SMF 4241 (formerly 1177.2a), an adult female, collected on an unknown date on ‘insula Nossi Bé’ (Nosy Be; approx. coordinates 13.2–13.4°S, 48.2–48.4°E), Diana Region, Madagascar, by Carl Ebenau (erroneously later designated as a lectotype by Mertens 1967) (Figs 8, 9, 11).

None. Boettger (1880a) states explicitly that the species is based on a single specimen.

Numerous specimens claimed to be syntypes/paralectotypes exist as a result of the erroneous designation of SMF 4241 as lectotype by Mertens (1967). We are not aware of an exhaustive list, but Barbour and Loveridge (1929) stated there were seven in the Museum of Comparative Zoology of Harvard, namely MCZ 2163 (one specimen), 2236 (one), 2731 (three), plus 9317 and 9318 (two). At least one of the specimens in MCZ 2731 was exchanged to the Field Museum of Natural History, where it is archived as FMNH 73363 and incorrectly listed as a ‘co-type’. A further specimen (EHT-HMS 44690, ex-SMF 4267) is listed as present in the type collection of the University of Illinois Museum of Natural History (Phillips 2015). This is also not a type. Four specimens formerly under catalogue number ZMB 10059 (now divided into ZMB 10059 [one specimen] and 51041–51043) were also originally incorrectly included in the catalogue of the Museum für Naturkunde, Berlin as types of R. testudo, but this was corrected in the digital catalogue.

We here examined SMF 4247–4263 (16 specimens), which Mertens (1967) incorrectly considered paralectotypes—none of these specimens in fact has type status. Additionally, we examined ZSM 474/2000 (FGMV 2000.276) and ZSM 475/2000 (FGMV 2000.277), two adult specimens of uncertain sex, collected on 11 March 2000 on the east coast of Lokobe National Park (13.4133°S, 48.3342°E, 110 m a.s.l.), Nosy Be, Diana Region, northern Madagascar, by F. Glaw, K. Schmidt, and M. Vences; UADBA-A-FGZC 5620, an adult male, collected on 29 April 2019 on the Kindro trail, Ampasindava (13.4099°S, 48.3051°E, ca 80 m a.s.l.), Lokobe National Park, Nosy Be, Diana Region, northern Madagascar, by F. Glaw, M.D. Scherz, and A. Razafindraibe (Fig. 10); and ZMB 51041, an adult female, collected in 1887 on Nosy Be (no precise collection data), Diana Region, northern Madagascar, by C. Reuter (originally part of ZMB 10059). We further examined photographs of the false ‘syntypes’, MCZ 2163, MCZ 9317, and MCZ 9318, to confirm their identity and morphological agreement with the holotype.

All referred specimens are unambiguously assigned to the species based on their overall morphology (the rotund body, short limbs, and chin barbels are unmistakable) and collection around the type locality. ZSM 475/2000 is used as the reference specimen for this species in 16S rRNA barcoding (16S3’ EU341110/AY594125; 16S5’ EU341110/AY594087; Vieites et al. 2009); a sample from either this specimen or ZSM 474/2000, with the tissue number MV 2000-B59, was used as the reference for COI barcoding (COIKF611596/MH940140; Perl et al. 2014). These specimens cluster in our mitochondrial phylogeny (Fig. 2). Both specimens are included in the RAG1 haplotype network (Fig. 4).

Type species of the genus Rhombophryne. Within the R. testudo group, this species is sister to R. matavy (Fig. 2; Belluardo et al. 2022). It is characterised by having the following unique suite of characters: (1) medium to large body size, adult SVL 33.0–43.1 mm; (2) head much wider than long (HW/HL 2.00–2.60); (3) small eyes (ED/HL 0.23–0.39); (4) short hindlimbs (HIL/SVL 1.18–1.41); (5) large inner metatarsal tubercle (IMTL/FOL 0.15–0.24); (6) generally pronounced outer metatarsal tubercle; (7) second finger slightly shorter than fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin rough with converging paravertebral ridges; (10) presence of chin barbels; (11) absence of pronounced superciliary spines; (12) absence of inguinal ocelli or spots; (13) absence of distinctive markings along the posterior thigh; (14) highly robust skull with very broad squamosal, maxilla, and posterior process of angulosplenial; (15) clavicles absent; and (16) advertisement call (based on 4 analysed calls by one individual) highly pulsed (162–177 pulses per call), with (17) call duration 823–894 ms, (18) inter-call interval 6071–10186 ms, and (19) dominant frequency 508–524 Hz.

Rhombophryne testudo is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘T’ at site 456, ‘T’ at site 651 and ‘C’ at site 734; in 16S3’, ‘C’ at site 1099, ‘C’ at site 1179, and ‘G’ at site 1216.

Within the genus Rhombophryne, R. testudo can easily be distinguished from all other species by the presence of several distinct chin barbels and its fortified skull, and from all species except R. coudreaui, R. matavy, and R. maraoraosp. nov. described below by its rotund body. From R. matavy it can further be distinguished by its pulsed (vs tonal) advertisement call that is much longer (call duration 823–894 ms vs 161–209 ms), and with a lower dominant frequency (508–524 Hz vs 1588–1688 Hz).

A specimen in a good state of preservation, quite stiff and hard, somewhat desiccated (Figs 8, 9). Developing eggs evident in a micro-CT scan of the specimen.

Body robust, rhomboid. Head very wide and short, much wider than long (HW/HL 2.45). Eyes small, pupils small, round. Snout obtuse, slightly protruding and rounded in dorsal view, angular in lateral view, with five barbels on it, two slightly above and between the nostrils, two directly below these, and a central one below these over the commissure of the jaws. Canthus rostralis distinct, convex. Loreal region concave, slightly oblique. Nostril openings small, angled anterolaterally, equidistant between tip of snout and eye, slightly protuberant. Tympanum indistinct, vertically oval. TDH/ED 0.827. Supratympanic fold distinct, weakly raised but tubercular and so uneven in height, forming a gentle curve from the line of the top of the eye over the tympanum, sloping down to the posterior of the top of the arm. Superciliary spines are absent but there is a small light-coloured spot centrally above each eye, with several small tubercles on the dorsal surface of the eye.

The jaw is firmly shut, such that it is impossible to open without damaging the specimen irreparably. The original description described the specimen as lacking maxillary teeth, having small and weak palatal bones (interpreted as the neopalatines), a simple unfringed ‘fold’ on the palate, which is interpreted as being the vomerine ridge, as the species lacks proper vomerine teeth (see Variation below), and having a large tongue that is wider than it is long, attached anteriorly and posteriorly free with a longitudinal furrow but without lateral emargination. Given that the jaw is so tightly shut, it is not clear how this information was obtained.

Forelimbs relatively short and thick, the upper arm hardly distinguishable from the trunk (FARL/SVL 0.397). Fingers without webbing, all short, relative lengths 1 < 2 = 4 < 3 (Fig. 9). Finger subarticular tubercles indistinct, single, round; inner metacarpal tubercle large, slightly shorter than first finger (IMCL/HAL 0.278); outer metacarpal/palmar tubercle indistinct, single. Hind limb thick, tibiotarsal articulation extent when adpressed anteriorly along the body cannot be assessed due to strong fixation. TIBL/SVL 0.259. Inner metatarsal tubercle present, large, longer than first toe, roughly as long as second toe (IMTL/FOL 0.193). Outer metatarsal tubercle faint. Toes not webbed; first toe distinctly reduced, toe lengths 1 < 2 < 5 < 3 < 4, fifth toe distinctly shorter than third; subarticular tubercles indistinct, single and round; toe tips not enlarged. Finger and toe tips without circum-marginal grooves (Fig. 9).

Dorsal skin smooth, with numerous tubercles on the flanks and limbs and along the jaw, and especially a number of barbels on the bottom lip. The ventral skin is wrinkled but smooth. Symmetrical converging ridges are present from behind the exoccipital region of the head running toward the cloaca, with a pair of less distinct, less extensive ridges between them from the posterior head to roughly the level of the suprascapulae.

After at least 137 years in preservative, the colouration of the specimen is still brown and does not appear to have faded except perhaps in a blemished area on the right side of the dorsum at roughly the level of the ilia. The brown base colour has darker-brown symmetrical markings, which consist of a chevron running from the medial inguinal region to the centre of the dorsum and two dark irregular patches posterior to the suprascapular region. The tubercles and digits of the hands and feet are cream, and there is a fine cream line defining the fold between the dorsal and ventral posterior thigh. A single dark brown crossband is present on the shank, one on the tarsus, and one on the lateral foot that matches with that of the shank when the leg is fully folded. The ventral colour is as the dorsum, but lighter brown over the chin and with a curious translucent spot on the ventral abdomen. The colour of the specimen in life is unknown.

SVL 33.0–43.1 mm (n = 18); full measurements are presented in Table S5. Most specimens could not be sexed because we did not have permission to dissect them, and the jaws of most specimens were so firmly fixed shut that we could not open the mouth and search for traces of vocal slits. Overall morphology is highly consistent. The tongue is broad and disc-like, posteriorly free. Maxillary teeth are absent. The vomerine teeth ridges form two straight transversal rows posterior to the rounded choanae, not meeting medially. The second and fourth fingers can vary in which is longer. There is a little variation in colouration, with some individuals uniformly brown in dorsal colour and others with dark-brown markings (e.g., Fig. 10).

The advertisement call recorded in January or February 1992 at Nosy Be (air temperature unknown) consists of a long, pulsed note emitted at irregular intervals (Fig. 12); calls are not arranged in call series. Pulses within calls are generally narrowly spaced and partly fused, but pulse repetition is distinctly faster in the second half of each call and results in respective parallel frequency bands reflecting pulse rate. Amplitude within calls is constantly increasing from the beginning towards the end where it drops to zero quickly. Numerical parameters of 4 analysed calls are as follows: call duration (= note duration) 823–894 ms (854 ± 30 ms); inter-call intervals 6071–10,186 ms (8370 ± 2100 ms); pulses per call 162–177 (169 ± 7); pulse repetition rate within first half of call approximately 135 pulses/second, within second half approximately 280 pulses/second; dominant frequency 508–524 Hz (519 ± 7 Hz); prevalent bandwidth 500–3200 Hz. Calls from the same recording (Vences et al. 2006, CD 3, track 33) have been described by Glaw and Vences (1992), D’Cruze et al. (2010), and Lambert et al. (2017) using slightly different terminological schemes.

Feminine nominative Latin noun meaning ‘turtle’ or ‘tortoise’, presumably in reference to the short limbs and rotund body shape of this species.

Confirmed from (1) Nosy Be (type locality), and (2) Nosy Komba (Glaw and Vences 1992; Andreone et al. 2003; Hyde Roberts and Daly 2014). Elevation: 0–450 m a.s.l. (the peak of Mt Lokobe on Nosy Be).

Records from Réunion (Guibé 1978) resulted from a clerical error when information were being copied from one catalogue to another, and were corrected by Glaw and Vences (2002). A record from ‘Imerina’ by Parker (1934) is based on BMNH 1895.10.29.30, collected by Richard Baron. The location Imerina could refer to anywhere across the high plateau of central Madagascar (the area where Baron served as a reverend; Laurence 1987). Baron was one of the most widely travelled explorers of that time, and the lack of precise collection date means that refinement of locality is challenging. However, it should be noted that Baron undertook an enormous journey from central-eastern Madagascar, along the coast north to Antsiranana, and then down the west coast to Nosy Be (a journey of almost 2000 km), collecting plants along the way (JSTOR Global Plants correspondence KADC2664 from Library and Archives at Royal Botanic Gardens, Kew). It is therefore conceivable that the location is an error; that Baron collected the specimen in Nosy Be at the end of his journey and sent it along with the consignment of plants to London. Examination of this specimen revealed it to be an adult male. It does not have any evident morphological differences from other R. testudo specimens. However, as stated above, a museomic sample of this specimen confirmed it to have moderately strong genetic differentiation from other R. testudo specimens. A BLASTn search of every contig in NCBI, however, consistently identified Rhombophryne testudoZSM 475/2000 as closest match, and with a sequence coverage of 4.9× and 2.9× for 16S3 and 16S5, respectively, it remains possible that a genetically divergent lineage is present in Imerina (or at some other location along Baron’s travel routes), which would be in need of re-discovery to verify. Records from Marojejy and Andapa-Sambava (Guibé 1978; Blommers-Schlösser and Blanc 1991; probably deriving from the same specimen, see Glaw and Vences 2002) referred to R. coudreaui by Andreone and Randrianirina (2008), but are here referred to R. maraoraosp. nov., described below.

Rhombophryne testudo is a fossorial species found in primary and secondary low-elevation humid forest, where it inhabits burrows 5–10 cm deep beneath the leaf litter (Glaw and Vences 1994). Calls are emitted from January to April, at highest intensity before and during heavy rain, irrespective of the time of day (Glaw and Vences 1994). Calling can occur without rain, but a series of two or three calls is then followed by a long pause of several minutes (Glaw and Vences 1994). Köhler et al. (1997) reported finding a 10 cm wide, 15 cm deep nest beneath a rock beside a small creek, containing two adults and 18 juveniles measuring 9–11 mm in SVL, in December 1995. This suggests development occurs in subterranean burrows with parental care, perhaps by both parents (Köhler et al. 1997). No tadpoles or eggs of the species have yet been observed.

A defensive behaviour is known wherein specimens stretch their hindlimbs to prevent them being turned onto their backs (Glaw and Vences 1994). We have also observed individuals puff themselves up significantly when caught, presumably to make them more difficult to swallow—common behaviours in burrowing microhylid frogs.

Keefe and Blackburn (2020) compared the humerus of Rhombophryne testudo to other burrowing frogs. They noted its similarity to forward-burrowers, suggesting that it may also be able to burrow forwards, but highlighting the need for behavioural observations of this species.

The gut of the holotype contains a great deal of soil, as evident from our micro-CT scans (Fig. 11). We examined the contents of the digestive system of an adult female specimen (with well-developed eggs), ZMB 51041. The stomach contained mostly detritus, especially tiny fragments of wood and leaves. Fragments of two insects were present in this detritus: the 4.7 mm abdomen of a small rove beetle (Staphylinidae), and the thorax and partial abdomen of an ant. The intestines contained mostly a fine mud with tiny fragments of wood and leaf, the head of an ant, and the thorax and head of the same rove beetle. By volume, the vast majority of gut contents was non-animal material. This suggests that most of the ingested matter of these frogs might be substrate, not insects. Although unlikely, more ecological research is needed to understand if these animals may be partly detritivorous or geophagous. However, it is more likely that insect larvae, annelid worms, or other soft-bodied organisms are the primary prey of these frogs, and are digested quickly and thus absent from the digestive system of preserved frogs.

The karyotype of this species was described by Aprea et al. (2007), with 2n = 26 largely metacentric chromosomes (second and third pairs submetacentric, fourth pair subtelocentric/telocentric). Nucleolar organiser regions were in a pericentromeric position on the short arm of the second chromosome pair. Heterochromatin was indistinct, and Chromomycin A₃ (CMA₃) and 4',6-diamidino-2-phenylindole (DAPI) negative, i.e., lacking particularly GC- or AT-rich regions.

MNHN 1937.19, an adult female, collected in January 1937 from ‘Réserve de Betampona (forêt orientale, près de Moramanga, à mi-chemin, entre Tamatave et Tananarive)’ (Angel 1938: 261), today the Réserve Naturelle Intégrale de Betampona, Antsinanana Region, eastern Madagascar (approx. coordinates 17.9°S, 49.2°E), by M. Coudreau (Figs 8, 9, 14).

None.

MRSN A6280 (FAZC 13600), an unsexed adult, collected on 12 February 2007 at Sahambendrana (17.8984°S, 49.2154°E, 458 m a.s.l.), Betampona Strict Nature Reserve, Antsinanana Region, eastern Madagascar, by G. de Sousa Miranda Rosa and F. Andreone (Fig. 13A–C); MRSN A6347 (FAZC 13887), an adult male, collected on 17 November 2007 at Maintimbato (17.8940°S, 49.2283°E, 255 m a.s.l.), Betampona Strict Nature Reserve, Antsinanana Region, eastern Madagascar, by G. de Sousa Miranda Rosa, F. Andreone, and J. Noel; MRSN A6267 (FAZC 13624) and MRSN A6271 (FAZC 13653; Fig. 13D–G), two unsexed individuals, collected on 19 February 2007 at Maintimbato (17.8940°S, 49.2283°E, 255 m a.s.l.), Betampona Strict Nature Reserve, Antsinanana Region, eastern Madagascar, by G. de Sousa Miranda Rosa.

The specimen MRSN A6347 is used as the reference specimen for this species in 16S rRNA barcoding (16S3’ FJ559299/HM364772; Vieites et al. 2009). All referred material agrees morphologically with the holotype, and is topotypical. Assignment of MRSN A6271, MRSN A6267 and MRSN A6280 is further confirmed by molecular taxonomic identification (Fig. 2). An additional tissue sample from a topotypical individual (not collected), DLR 550 (tissue number ACZC 7731) is present in the RAG1 haplotype network (Fig. 4).

Within the R. testudo group, this species is sister to R. maraoraosp. nov. (described below) based on molecular phylogenetic data (Fig. 2; Belluardo et al. 2022). It is characterised by the possession of the following unique suite of characters: (1) small to medium body size, adult SVL 21.5–26.4 mm; (2) head much wider than long (HW/HL 1.65–1.85); (3) small eyes (ED/HL 0.29–0.31); (4) short hindlimbs (HIL/SVL 1.17–1.30); (5) large inner metatarsal tubercle (IMTL/FOL 0.15–0.18); (6) generally indistinct outer metatarsal tubercle; (7) second finger equal in length to fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin rough to rugose with converging longitudinal rows of tubercles; (10) presence of few, small chin barbels; (11) absence of pronounced superciliary spines; (12) absence of inguinal ocelli or spots; (13) absence of distinctive markings along the posterior thigh; (14) broad but not fortified skull, without expansion of squamosal, maxilla, or posterior process of angulosplenial; and (15) clavicles absent.

Rhombophryne coudreaui is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘C’ at site 259, and ‘T’ at site 329 and ‘T’ at site 348. No diagnostic sites were identified for 16S3’.

Within the genus Rhombophryne, R. coudreaui can easily be distinguished from all other species except R. testudo, R. matavy, and R. maraoraosp. nov. described below by its flattened, rotund body and short, broad head. Among these species, see the account of R. testudo above for distinction from that species; it can be distinguished from R. matavy by smaller body size (SVL 21.5–26.4 mm vs 40–50 mm), rougher dorsal skin, and less fortified skull; for distinction from R. maraoraosp. nov., see the description of that species, below. Rhombophryne coudreaui may also differ from all other Rhombophryne species by the absence of carpal 2 in the hand (vs presence); see the ‘Osteology of the Rhombophryne testudo species group’ below for discussion.

A specimen in a mediocre state of preservation, with its arms and legs stretched straight and several broken bones (Figs 8, 9, 14; see osteology, below). An incision made along the left flank makes ova visible and has torn the stomach, which evidently contains the remains of some arthropods, but which we have not emptied.

Body robust and rotund, stout. Head very wide and short, much wider than long (HW/HL 1.72). Eyes small, pupils round. Snout rounded in dorsal view, rounded in lateral view. A few small chin barbels. Canthus rostralis distinct, concave. Loreal region concave, slightly oblique. Nostril openings small, angled laterally, closer to tip of snout than to eye, slightly protuberant. Tympanum indistinct, round. TDH/ED 0.824. Supratympanic fold distinct, raised, from posterior corner of eye straight over tympanum, then slightly curving downward. There are a few tiny bumps above each eye, which do not form distinct superciliary spines. Maxillary and vomerine teeth present, vomerine teeth distinct, each straight row bearing a diastema in its middle, separated from the contralateral at the midline by a small gap. Choanae oblong. Tongue very broad, round, attached anteriorly, posteriorly free.

Forelimbs relatively short and thick, the upper arm hardly distinguishable from the body cavity (FARL/SVL 0.321). Fingers without webbing, all short, relative lengths 1 < 2 = 4 < 3. Finger subarticular tubercles distinct, large and flat; inner metacarpal tubercle large (IMCL/HAL 0.289); outer metacarpal/palmar tubercle paired. Hind limb thick, tibiotarsal articulation extent when adpressed anteriorly along the body cannot be assessed due to the many broken bones in the legs. TIBL/SVL 0.302. Inner metatarsal tubercle present, large (IMTL/FOL 0.178). Outer metatarsal tubercle absent. Toes not webbed; first toe strongly reduced, second toe moderately reduced, toe lengths 1 < 2 < 5 < 3 < 4, fifth toe distinctly shorter than third; subarticular tubercles indistinct, single and round; toe tips not enlarged.

The dorsal skin is rather rough, with notable tubercles outlined in dark brown above the suprascapular and sacral regions. The ventral skin is as rough as the dorsal. Along the lower lip there are a series of small barbels, especially two on either side of the medial symphysis a little behind the line of the jaw.

After at least 83 years in preservative, the colouration of the specimen is pale creamy brown, with darker areas on the forearms and the areas of the body that are covered in the fixed specimen, such as the axillae. The ventral surface is a more homogeneous light brown. Distinctive dark brown markings surround the tubercles on the suprascapular and sacral regions, but otherwise the dorsum is rather homogeneous in colour. The hindlimbs have lost most colouration, but a distinctive cream tubercle surrounded in brown is present on each shank. The forelimbs are ventrally dark brown on the lower arm, with a brown crossband anteriorly; pale and indistinctly patterned on the upper arm. The colour of the specimen in life is unknown.

SVL 21.5–26.4 mm (n = 5); full measurements are presented in Table S5. The base colouration of all recently collected specimens is a dark chocolatey brown (see Fig. 13 for an idea of colour variation in life). Much of the body patterning is consistent, especially the dark suprascapular spots which define the short edge of a trapezium where the eyes mark the long edge. MRSN A6271 has a chin marbled with cream and also has cream spots on its anterior thigh and interior shank; no other examined specimen shares these patterns.

The call of this species is not known.

Eponym for Mr. Coudreau, ‘Conservateur des Réserves naturelles de Madagascar’ (Angel 1938).

This species is confined to low-elevation forests in eastern Madagascar, and is with certainty known only from (1) Réserve Naturelle Intégrale de Betampona (type locality), where it has been found at Sahambendrana, Maintimbato and Sahaindrana (Rosa et al. 2012) as well as at Sahabefoza (17.9142°S, 49.2078°E, 353 m a.s.l.). However, S. Andrianarivo provided MDS photographs clearly assignable to this species from (2) Ampasina, a highly degraded forest just 8 km east of Betampona (17.918°S, 49.323°E, ca 80 m a.s.l.), taken on 2 October 2022. This indicates that the species is present and may be able to persist in strongly anthropogenically altered forest. Elevation: ca 80–200 m a.s.l.

The record from Ambolokopatrika-Betaolana (Andreone 2003) unambiguously refers to R. maraoraosp. nov. (described below), as it is based on the type material of that species. The specimen MNHN 1973.576 from Marojejy in the northeast of Madagascar was assigned to R. coudreaui by Andreone and Randrianirina (2008), but the material used for comparison to R. coudreaui was also from the northeast and is described as a new species, R. maraoraosp. nov., below. Based on the locality of this specimen and its apparent affinity with R. maraoraosp. nov., we consider it likely that MNHN 1973.576 is referrable to that species, and therefore remove Marojejy from the locality record of R. coudreaui. The same applies also to other records from Marojejy (Raselimanana et al. 2000) and Maroantsetra (IUCN SSC Amphibian Specialist Group 2016d).

Rhombophryne coudreaui is a fossorial species restricted to low-elevation humid forest that is seldom encountered and poorly known. This species exhibits a death-feigning behaviour beyond normal tonic immobility wherein it straightens and stiffens all four limbs (Fig. 13F). One specimen was found at Sahaindrana campsite (Betampona Strict Nature Reserve) walking on the leaf litter in the early hours of the morning (around 6 am). Two individuals were found underneath wet leaf litter and rotten logs in almost-closed-canopy humid forest on the ridge at 460 m at 10:40 am in Sahabefoza.

This species is only known from the type series.

This species was listed as ‘Rhombophrynesp. nov.’ by D’Cruze et al. (2008), and ‘Rhombophryne sp. 8’ by Vieites et al. (2009).

ZSM 1628/2008 (FGZC 1888), an adult male, collected on 27 February 2008, in Forêt d’Ambre Special Reserve (now part of Montagne d’Ambre National Park) (12.4628°S, 49.2233°E, 482 m a.s.l.), Diana Region (part of former Antsiranana Province), northern Madagascar, by N. D’Cruze, F. Glaw, J. Köhler, and local guides (Figs 8, 9, 15, 16).

Three specimens: ZSM 1629/2008 (FGZC 1889), UADBA-A-FGZC 1890, and UADBA-A-FGZC 1891, three adult males with the same collection data as the holotype except that UADBA-A-FGZC 1891 was collected on 28 February 2008.

The holotype is used as the reference specimen for this species in 16S rRNA barcoding (16S3’ FJ559298; Vieites et al. 2009) and COI barcoding (COIKF611589; Perl et al. 2014). All paratypes agree morphologically with the holotype, and are topotypical. Assignment of UADBA-A-FGZC 1890 is further confirmed by molecular taxonomic identification (Fig. 2). ZSM 1628/2008 is present in the RAG1 haplotype network (Fig. 4).

Within the R. testudo group, this species is sister to R. testudo based on molecular phylogenetic data (Fig. 2; Belluardo et al. 2022). It is characterised by the possession of the following unique suite of characters: (1) large body size, adult SVL 40–50 mm (see ‘Variation’ below for discussion of these values); (2) head much wider than long (HW/HL 1.88–2.05); (3) small eyes (ED/HL 0.24–0.28); (4) short hindlimbs (HIL/SVL 1.17–1.25); (5) large inner metatarsal tubercle (IMTL/FOL 0.21–0.26); (6) pronounced outer metatarsal tubercle; (7) second finger rough equal in length to fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin with scattered warts and ridges; (10) absence of chin barbels; (11) absence of pronounced superciliary spines; (12) absence of inguinal ocelli or spots; (13) absence of distinctive markings along the posterior thigh; (14) broad and slightly fortified skull, but without expansion of maxilla or posterior process of angulosplenial; and (15) clavicles absent; and (16) advertisement call (based on 15 analysed calls by one individual) tonal, with (17) call duration 161–209 ms, (18) inter-call interval 267–353 ms, and (19) dominant frequency 1588–1688 Hz.

Rhombophryne matavy is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘T’ at site 474, ‘T’ at site 475, and ‘C’ at site 538; in 16S3’, ‘A’ at site 1018, ‘C’ at site 1072, and ‘T’ at site 1078.

Within the genus Rhombophryne, R. matavy can easily be distinguished from all other species except R. testudo, R. coudreaui, and R. maraoraosp. nov. described below by its rotund body and short, broad head. Among these species, see the accounts of R. testudo (its sister species) and R. coudreaui above for distinction from those species; for distinction from R. maraoraosp. nov., see the description of that species, below.

Adult male SVL 44.6–45.1 mm (n = 2); full measurements are presented in Table S5. D’Cruze et al. (2010) measured the same specimens and reported their SVLs to be substantially larger (46.7–47.6 mm). The reason for the discrepancy in measured size is not clear. D’Cruze et al. (2010) also measured two paratypes, UADBA-A-FGZC 1890 and 1891, as 39.4 and 49.4 mm, respectively. For this reason, we have given the SVL in the diagnosis above as between 40 and 50 mm.

The advertisement call of the holotype (ZSM 1628/2008), recorded on 27 February 2008 at Forêt d’Ambre Special Reserve (air temperature unknown), consists of a tonal note of moderate duration emitted in regular call series containing 5 calls repeated at regular succession (n = 3; Fig. 17). Each call exhibits considerable amplitude modulation, with highest energy present at approximately the last third of the call’s duration. Slight upward frequency modulation is evident in each call, followed by a fast terminal drop in frequency. Numerical parameters of 15 analysed calls are as follows: call duration (= note duration) 161–209 ms (183 ± 14 ms); inter-call intervals within regular call series 267–353 ms (299 ± 22 ms); number of calls per call series 5 (5.0 ± 0.0); duration of regular call series 2091–2202 ms (2130 ± 48 ms); dominant frequency 1588–1688 Hz (1652 ± 16 Hz); prevalent bandwidth 750–6800 Hz; frequency bands recognizable at approximately 880, 2500, 3360, 4160, 5060, and 5840 Hz. Calls from the same recording have been described by D’Cruze et al. (2010) using a slightly different terminological scheme.

The Malagasy adjective matavy meaning ‘fat’, in reference to the body shape of the species, especially when inflated (D’Cruze et al. 2010). Used as an invariable noun in apposition.

This species is only known from (1) the low-elevation parcel of forest in Montagne d’Ambre National Park, formerly known as Forêt d’Ambre Special Reserve (type locality). Elevation: ca 482 m a.s.l.

Rhombophryne matavy is a fossorial species found in low-elevation humid forest; its ecology is poorly known, but presumably much like its sister species, R. testudo. Highest calling activity (in choruses) was noticed during and just after rain, and the specimens were collected at night, mostly up to 5 cm deep in the leaf litter, though one was found active on top of it (D’Cruze et al. 2010). D’Cruze et al. (2010) noted a defensive behaviour involving the stretching of the limbs and arching the back, like R. testudo. They reported the faeces of one individual (ZSM 1628/2008) to include the remains of several insects, including beetles.

This species was referred to as R. minuta by Glaw and Vences (1992), where its call and morphology were first described.

One sequence belonging to this species, KU724182 in GenBank, is erroneously ascribed to collection number ZCMV 891 (corresponding to ZSM 463/2005, a Platypelis grandis); the actual R. mangabensis specimen to which this sequence belongs is ZCMV 890.

The call was published as ‘Plethodontohyla sp. (Nosy Mangabe)’ by Vences et al. (2006). This species was listed as ‘Rhombophryne sp. aff. minuta’ by Glaw and Vences (2007), as ‘Rhombophryne sp. 2 Nosy Mangabe’ by Wollenberg et al. (2008), and as ‘Rhombophryne sp. 5’ by Vieites et al. (2009).

ZSM 470/2005 (ZCMV 886), an adult male, collected on 22 February 2005 on ‘Nosy Mangabe island’ (ca 15.50°S, 49.77°E, ca 50–100 m a.s.l.), Analanjirofo Region, northeastern Madagascar, by F. Glaw, R.D. Randrianiaina, and M. Vences (Figs 8, 9, 19).

Eight specimens: ZSM 471/2005 (ZCMV 2118), ZSM 472/2005 (ZCMV 2154), UADBA-A-ZCMV 2119, and UADBA-A-ZCMV 890, three adult specimens (probably males) and one subadult, with the same collection data as the holotype (Fig. 18A–C); ZFMK 52769–52771, three adult males, and ZFMK 52772, one subadult specimen, all collected on 13 March 1991 at the type locality, by F. Glaw and M. Vences (ZFMK 52769 is shown in Fig. 18D).

ZSM 1573/2009, a subadult, collected in May/June 2003 on Nosy Mangabe (15.4959°S, 49.7693°E), Analanjirofo Region, northeastern Madagascar, by N. Lutzmann; ZSM 262/2016 (FGZC 5417), an unsexed adult, collected on 10 August 2016 near the ‘Eco-Lodge chez Arol’ (ca 15.712°S, 49.964°E, 21 m a.s.l.), Masoala Peninsula, Analanjirofo Region, northeastern Madagascar, by F. Glaw, D. Prötzel, J. Forster, K. Glaw, and T. Glaw; MRSN A2557, an unsexed adult, collected on 8 February 2002 at ‘Camp 2’ Mahalevona (ca 15.4178°S, 49.9410°E, ca 669 m a.s.l.), Masoala Peninsula, Analanjirofo Region, northeastern Madagascar, by J.E. Randrianirina; UADBA-A-APR12051 (Fig. 18E), an unsexed specimen, collected on 25 November 2015 at Ambohitsitondroina (15.5694°S 50.0034°E, 609 m a.s.l.), Masoala National Park, Analanjirofo Region, northeastern Madagascar, by A. Raselimanana.

The holotype is used as the reference specimen for this species in 16S rRNA barcoding (16S3’ EU341109/KU724181; 16S5’ EU341109; Vieites et al. 2009) and COI barcoding (COIKF611588/KU937775; Perl et al. 2014). All paratypes and referred specimens conform well with the holotype in morphology. The paratypes are all topotypical. Assignment of specimens ZSM 471/2005, UADBA-A-ZCMV 2119, MRSN A2557, and ZSM 262/2016 is further confirmed by molecular taxonomic identification (Fig. 2). MRSN A2557 and ZSM 262/2016 are present in the RAG1 haplotype network (Fig. 4).

Within the R. testudo group, this species is sister to R. savaka based on molecular phylogenetic data (Fig. 2; Belluardo et al. 2022). It is characterised by the possession of the following unique suite of characters: (1) small body size, adult SVL 19.6–23.2 mm; (2) head wider than long (HW/HL 1.60–1.86); (3) moderately small eyes (ED/HL 0.34–0.38); (4) short hindlimbs (HIL/SVL 1.54–1.60); (5) small inner metatarsal tubercle (IMTL/FOL 0.09–0.12); (6) indistinct outer metatarsal tubercle; (7) second finger roughly equal in length to fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin finely granular with a few scattered warts, especially a suprascapular pair outlined in black; (10) absence of chin barbels; (11) absence of pronounced superciliary spines; (12) absence of inguinal ocelli or spots; (13) absence of distinctive markings along the posterior thigh; (14) unfortified skull without expansion of maxilla or posterior process of angulosplenial; (15) clavicles reduced, thin, curving; and (16) advertisement call (based on 20 analysed calls by one individual) tonal, with (17) call duration 180–237 ms, (18) inter-call interval 419–822 ms, and (19) dominant frequency 3300–3550 Hz.

Rhombophryne mangabensis is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘A’ at site 383, ‘G’ at site 567 and ‘C’ at site 641; in 16S3’, A’ at site 917, ‘A’ at site 1088, ‘G’ at site 1090, and ‘A’ at site 1127.

Within the genus Rhombophryne, R. mangabensis can easily be distinguished from all members of the R. serratopalpebrosa species group by the absence of superciliary spines (vs presence); from members of the R. minuta species group by less gracile body and much shorter limbs; from R. proportionalis by its much larger body size (SVL 19.6–23.2 mm vs 11.0–12.3 mm); from members of the R. ellae species group by the absence of inguinal spots and reddish orange colouration on the hindlimbs (vs presence); from members of the R. laevipes species group by the absence of inguinal spots or ocelli (vs presence in most species), and smaller adult body size (SVL 19.6–23.2 mm vs 24.1–57.2 mm). Within the R. testudo species group, see accounts of R. testudo, R. coudreaui, and R. matavy above for distinction from those species. From its sister species, R. savaka, it can be distinguished by the less pronounced diastema in vomerine teeth, slightly longer relative tibia length (TIBL/SVL 0.44–0.46 vs 0.37–0.42), absence of inguinal spots (vs presence), and by advertisement call with slightly longer call duration (180–237 ms vs 121–142 ms), generally longer inter-call interval (419–822 ms vs 302–451 ms), and lower dominant frequency (3300–3550 Hz vs 4144–4210 Hz). For distinction from newly described species, see accounts of those species, below.

SVL 19.6–23.2 mm (n = 4 adults; two presumed subadults measure 16.5 and 18.9 mm, respectively); full measurements are presented in Table S5. Measurements are largely consistent with those given in the original description by Glaw et al. (2010b). All specimens are consistent in morphology and colouration, including the newly referred specimens from mainland Madagascar (ZSM 262/2016 and MRSN A2557). Two raised black markings with small light brown points in the suprascapular region are consistently present as part of the variably complete anterior chevron marking; a posterior chevron running from the inguinal region anteriorly over the dorsum is sometimes incomplete at the midline but is usually indicated (Fig. 18A, C–E). Shanks often exhibit a broad middle stripe and two narrow stripes proximal and distal to this stripe (Fig. 18A, C–E).

The advertisement call recorded on 13 March 1991 at Nosy Mangabe (air temperature unknown) consists of a tonal note of moderate duration emitted in regular call series containing a variable number of calls (2–5) repeated at rather regular succession (Fig. 20). Each call exhibits some irregular amplitude modulation, with 2 or 3 peaks recognizable within each call, with the terminal peak having the highest energy. Slight upward frequency modulation is evident in each call until the last third of the call’s duration, followed by a terminal drop in frequency. Numerical parameters of 20 analysed calls are as follows: call duration (= note duration) 180–237 ms (198 ± 15 ms); inter-call intervals within regular call series 419–822 ms (484 ± 113 ms); duration of regular call series 820–2895 ms (1779 ± 925 ms); dominant frequency 3300–3550 Hz (3434 ± 85 Hz); prevalent bandwidth 2800–7500 Hz; weak frequency bands recognizable at approximately 5250 and 6760 Hz. Calls from the same recording (Vences et al. 2006, CD 3, track 31) have been described by Glaw et al. (2010b) using a slightly different terminological scheme.

Toponym referring to Nosy Mangabe, the island where the species was originally discovered.

This species was originally known only from (1) Nosy Mangabe (type locality), but its presence on the Masoala Peninsula was reported by Raherilalao et al. (2016) and confirmed by Belluardo et al. (2022). The extent of its range on the peninsula constitutes three further distinct sites: (2) Tampolo (under which we include the nearby ‘Eco-Lodge chez Arol’), (3) Mahalevona, and (4) Ambohitsitondroina (15.5694°S 50.0034°E, 609 m a.s.l.; Fig. 18E). Elevation: ca 15–669 m a.s.l.

Rhombophryne mangabensis is a semi-fossorial or detriticolous species found in low-elevation humid forest. Specimens were collected at night during heavy rain, during which many calls were heard in an intense chorus. Males called from concealed positions in the leaf litter of ‘apparently primary low-altitude rainforests’ (Glaw et al. 2010b: 240). Calling has not been directly observed, but the call described above certainly belongs to this species, as specimens caught while searching for the source of calling were inflated with air, typical for calling Rhombophryne. Active specimens were encountered on the forest floor during the day, in the evening, and at night. One individual was captured by pitfall traps set up in a valley with closed-canopy humid forest associated with thick leaf litter and many rotten logs.

Aprea et al. (2007) reported on the karyotype of ‘Rhombophryne sp. aff. minuta’ from Masoala, but the specimen number they reported, MRSN A3656, is from Manarikoba in Tsaratànana, and is therefore not referrable to this species, but in fact belongs to Rhombophryne quentinisp. nov., described below. The karyotype of R. mangabensis is therefore unknown.

This species was listed as ‘Rhombophryne sp. 4’ by Vieites et al. (2009) and Glaw et al. (2010b), and ‘Rhombophryne sp. Ca4’ by Perl et al. (2014).

ZSM 468/2005 (ZCMV 2065), an adult male, collected on 18 February 2005 at ‘Camp Marojejia’ (14.4350°S, 49.7605°E, 746 m a.s.l.), Marojejy National Park, Sava Region, northeastern Madagascar, by F. Glaw, M. Vences, and R.D. Randrianiaina (Figs 8, 9, 22).

One specimen: UADBA-A-ZCMV 2079, a specimen of unknown age and sex with the same collection data as the holotype.

ZSM 519/2016 (MSZC 0319; Fig. 21D–F) and KU 347465 (CRH 1653; Fig. 21A–C), two adult males (call vouchers), collected at night on 2 December 2016 near ‘Camp Mantella’ (ca 14.438°S, 49.776°E, 450 m a.s.l.), Marojejy National Park, Sava Region, northeastern Madagascar, by M.D. Scherz, J.H. Razafindraibe, C.R. Hutter, and A. Razafimanantsoa; ZSM 520/2016 (MSZC 0318; Fig. 21G–I), an adult female, collected at night on 1 December 2016 near ‘Camp Marojejia’ (14.4340°S, 49.7610°E, ca. 750 m a.s.l.), Marojejy National Park, Sava Region, northeastern Madagascar, by M.D. Scherz, J.H. Razafindraibe, C.R. Hutter, and A. Razafimanantsoa.

The holotype is used as the reference specimen for this species in 16S rRNA barcoding (16S3’ KU724176; Vieites et al. 2009) and COI barcoding (COIKF611594; Perl et al. 2014). The paratype and referred material conform well with the holotype in morphology, and were collected at or near the type locality. Assignment of specimens ZSM 519/2016, ZSM 520/2016, and UADBA-A-ZCMV 2079 is further confirmed by molecular taxonomic identification (Fig. 1). KU 347465 has been sequenced with the FrogCap hybrid capture probe set; it is included in the RAG1 haplotype network (Fig. 4).

Within the R. testudo group, this species is sister to R. mangabensis based on molecular phylogenetic data (Fig. 2; Belluardo et al. 2022). It is characterised by the possession of the following unique suite of characters: (1) small body size, adult SVL 18.8–20.9 mm; (2) head wider than long (HW/HL 1.66–1.80); (3) moderately small eyes (ED/HL 0.35–0.43); (4) short hindlimbs (HIL/SVL 1.37–1.55); (5) small inner metatarsal tubercle (IMTL/FOL 0.11–0.14); (6) moderately distinct outer metatarsal tubercle; (7) second finger roughly equal in length to fourth, except in one individual where it is much shorter than fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin finely granular with a few scattered warts, especially a suprascapular pair outlined in black; (10) absence of chin barbels; (11) absence of pronounced superciliary spines; (12) occasional presence of small black inguinal ocelli without light outline; (13) absence of distinctive markings along the posterior thigh; (14) unfortified skull without expansion of maxilla or posterior process of angulosplenial; (15) clavicles present, thin, curving; and (16) advertisement call (based on 28 analysed calls by one individual) tonal, with (17) call duration 121–142 ms, (18) inter-call interval 221–395 ms, and (19) dominant frequency 3714–3861 Hz.

Rhombophryne savaka is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘C’ at site 355, ‘G’ at site 664 and ‘T’ at site 687; in 16S3’, ‘A’ at site 937, ‘T’ at site 1094, and ‘T’ at site 1155.

Within the genus Rhombophryne, R. savaka can easily be distinguished from all members of the R. serratopalpebrosa species group by the absence of superciliary spines (vs presence); from members of the R. minuta species group by less gracile body and much shorter limbs; from R. proportionalis by its much larger body size (SVL 18.8–20.9 mm vs 11.0–12.3 mm); from members of the R. ellae species group by the absence of reddish orange colouration on the hindlimbs (vs presence); from members of the R. laevipes species group by the absence of white outline on inguinal spots or whitish inguinal spots (vs presence in most species), and smaller adult body size (SVL 18.8–20.9 mm vs 24.1–57.2 mm). Within the R. testudo species group, see accounts of R. testudo, R. coudreaui, R. matavy, and its sister species R. mangabensis above for distinction from those species. For distinction from newly described species, see accounts of those species, below.

SVL 18.7–20.9 mm (n = 3). For variation in other measurements, see Table S5.

A detailed description of the species is given in Scherz et al. (2016a), but it was based on just a single individual. Additional specimens collected in 2016 are very similar to the holotype (Fig. 21). The largest specimen is an ovigerous female, ZSM 520/2016 (Fig. 21G–I), but this specimen is only 0.5 mm larger than the male holotype. The skin was consistently rather smooth in all individuals. ZSM 519/2016 shows a large diastema in its vomerine teeth, consistent with the holotype. All specimens are consistent in overall colouration, but differ in details of patterning. ZSM 520/2010 has an extensive near-black bar on its lower posterior thigh, where the other specimens have only a small trapezoid. This specimen also has blackish spots above its suprascapular region and faint crossbands on its hindlimbs, which are lacking form the other specimens. Inguinal spots were present only in the holotype; ZSM 520/2016 has a diminutive inguinal spot on the right side but not the left. The posterior thigh is solid cream in colour. The abdomen is also immaculate cream in all specimens, and very translucent in life (Fig. 21C, F, I). At least one specimen (ZSM 520/2016) has dark markings above the suprascapular region, but these are not as distinctive or dark as in R. mangabensis or in R. mavokelysp. nov. described below.

The advertisement call recorded on 2 December 2016 at Camp 1, Marojejy National Park (call voucher ZSM 519/2016 [MSZC 0319]; air temperature 22.6 °C) during rainfall, consists of a tonal note of short duration emitted in short regular call series (Fig. 23). Inter-call intervals within call series tend to be slightly longer in duration towards the end of a series. Each call exhibits some slight amplitude modulation, with call energy moderately fast increasing towards the middle of the call, then keeping the same level of energy until the last quarter of the call’s duration when it quickly drops towards the call’s end. Slight upward frequency modulation is evident in each call until two thirds of the call’s duration, followed by a slight terminal drop in frequency. Numerical parameters of 28 analysed calls are as follows: call duration (= note duration) 121–142 ms (132 ± 5 ms); inter-call intervals within regular call series 221–395 ms (296 ± 45 ms); number of calls per call series 4–5 (4.3 ± 0.5); duration of regular call series 1342–1883 ms (1483 ± 187 ms); dominant frequency 3714–3861 Hz (3807 ± 47 Hz); prevalent bandwidth 1600–7800 Hz; frequency bands recognizable at approximately 1900, 5700, and 7680 Hz.

Additional calls recorded on 2 December 2016 at the same locality (voucher specimen KU 347465 [CRH 1653]) completely agree in general characteristics with the call described above, except for a slightly higher dominant frequency explainable by smaller body size of the calling male, and have the following numerical parameters (3 call series and 13 calls analysed): call duration (= note duration) 110–122 ms (115 ± 3 ms); inter-call intervals within regular call series 302–451 ms (340 ± 46 ms); number of calls per call series 4–5 (4.3 ± 0.6); duration of regular call series 1461–1932 ms (1631 ± 261 ms); dominant frequency 4144–4210 Hz (4175 ± 27 Hz); prevalent bandwidth 1800–8500 Hz.

The Malagasy noun savaka meaning ‘diastema’, in reference to the diastema in the vomerine teeth that were thought to be diagnostic of this species. Used as an invariable noun in apposition.

Rhombophryne savaka is known only from (1) Marojejy National Park (type locality). Elevation: 450–750 m a.s.l. (based on newly collected material). Records from 1300±200 m a.s.l. by Rakotoarimalala and Raselimanana (2023) cannot be verified as we have not examined material and have no DNA sequences, so they are here not included.

Rhombophryne savaka is a semi-fossorial or detriticolous species found in low- to mid-elevation humid forest. Calling activity was triggered by rain in November and December 2016, especially at night. Locally the species seemed rather common, though it was very difficult to localise calling individuals. Males emit advertisement calls from within or on the leaf litter; ZSM 519/2016 was observed calling with a leaf resting on its back. Females likewise live within the leaf-litter; ZSM 520/2016 was collected whilst attempting to find a calling male from within the same quadrat of leaf litter (the male could not be found).

Specimens assignable to this species were attributed to Rhombophryne testudo by Blommers-Schlösser and Blanc (1991) and Guibé (1978), as R. coudreaui by Andreone (2003), as both R. coudreaui and R. testudo by Glaw and Vences (2007), and as R. coudreaui by Andreone and Randrianirina (2008).

This species was listed as ‘Rhombophryne sp. 9’ by Vieites et al. (2009), ‘Rhombophryne sp. Ca09’ by Belluardo et al. (2022), and ‘Rhombophryne sp. 9’ and ‘CCS “Sp. 9”’ by Carné and Vieites (2024).

According to current knowledge, this is the allopatric sister lineage of R. coudreaui, which it also closely resembles morphologically. However, it is genetically highly divergent (10% uncorrected p distance in the 16S3’ fragment), there is no haplotype sharing with R. coudreaui or any other Rhombophryne species in the nuclear gene RAG1 (Fig. 4), and it has subtle but recognizable morphological differences (see Diagnosis below). We are therefore convinced that it represents an evolutionarily independent lineage.

MRSN A2115 (FN 7705), an adult male, collected on 2 December 1998 in the Ambatoledama Corridor (Andasin’i Governera) (ca 15.30°S, 50.02°E, 650 m a.s.l.), Masoala Peninsula, Sava Region, northeastern Madagascar, by F. Andreone and J.E. Randrianirina (Figs 8, 9, 24D, 25).

Three specimens: MRSN A2496 (no field number) and MRSN A2497 (RJS 0496), an adult female and a juvenile, respectively, collected on 8 February 2002 at ‘Camp 7’ Antsiranana Faritany (15.4177°S, 49.9403°E, ca. 800 m a.s.l.), Amparihy, Masoala Peninsula, Analanjirofo Region, northeastern Madagascar, by J.E. Randrianirina; MRSN A6929 (FN 7292), an adult male, collected on 13 December 1997 at ‘Camp 3’ Antsinjorano (14.5433°S, 49.4300°E, ca 950 m a.s.l.), Ambolokopatrika-Betaolana Forest, Sava Region, northeastern Madagascar by F. Andreone, G. Aprea & J.E. Randrianirina (Fig. 24A–C). Note: MRSN A6929 formerly bore the collection number MRSN A2066 (Andreone 2003), but this number was apparently duplicated, so a new number was issued.

MNHN 1973.576, an unsexed specimen, collected on 19 December 1972 at ‘Sambava, km 17 route d’Andapa’ near the Marojejy Massif, Sava Region, northeastern Madagascar, by C. Blanc. This specimen was assigned morphologically to ‘R. coudreaui’ by Andreone and Randrianirina (2008), but the material used for comparison to R. coudreaui in that work constitutes the type series of R. maraoraosp. nov., and does not include any material of R. coudreaui sensu stricto. Although we were not able to re-examine this specimen, its assignment to R. maraoraosp. nov. is partly supported by the textual description from Andreone and Randrianirina (2008: 47), ‘this specimen (likely a female 34.9 mm long) does not show an evident tympanum, lacks protruding jaw whiskers and shows the typical rhomboidal drawing on the head, and has a rather dark belly’. This assignment remains tentative, however, and requires confirmation by either morphological inspection or museomic sequencing.

MRSN A5524, originally reported by Andreone and Randrianirina (2008) as being from Tsingy de Bemaraha in western Madagascar, was found by Belluardo et al. (2022) to be genetically identical with R. maraoraosp. nov. Belluardo et al. (2022) showed that its locality was probably confused, and it is most likely from somewhere in northeastern Madagascar. It is referred to this species on genetic and morphological grounds, but its incorrect former locality is not considered as part of the distribution of the species. We also do not include it in the diagnosis of the species, but comment on how its morphology expands our knowledge of the species in the Variation section, below.

BMNH 1987.331, an unsexed possible subadult, collected on 31 August 1986 in Anandrivola Forest (15.775°S, 49.600°E, ca 580 m a.s.l.), Analanjirofo Region, northeastern Madagascar, by C.J. Raxworthy, is tentatively assigned to this species based on its small size, rotund body and short head, rough skin, and the second finger being slightly shorter than the fourth (the last character being the key feature distinguishing it from R. coudreaui; see Diagnosis, below).

Specimens previously attributed to R. coudreaui from Marojejy (Raselimanana et al. 2000) and Maroantsetra (IUCN SSC Amphibian Specialist Group 2016d) may be referable to R. maraoraosp. nov., as these two species are only now being recognised as distinct, with R. maraoraosp. nov. apparently occurring north of R. coudreaui. However, these records may also refer to R. mavokelysp. nov. (described below), which may look similar in its flat body profile and broad head, so carefuly scrutiny is warranted, and we do not include these locations in the distribution of this species.

The holotype is used as the reference specimen for this species in 16S rRNA barcoding (16S5’ AY594072; Andreone et al. 2005; 16S3’ AY594110; Vieites et al. 2009). All paratypes and referred specimens conform well with the holotype in morphology. Assignment of MRSN A2497 is further confirmed by molecular taxonomic identification. MRSN A2115 and MRSN A2497 are present in the RAG1 haplotype network (Fig. 4).

Within the R. testudo group, this species is sister to R. coudreaui based on molecular phylogenetic data (Fig. 2; Belluardo et al. 2022). It is characterised by the possession of the following unique suite of characters: (1) small to medium body size, adult SVL 22.5–28.9 mm; (2) head much wider than long (HW/HL 1.69–1.88); (3) small eyes (ED/HL 0.25–0.27); (4) short hindlimbs (HIL/SVL 1.10–1.28); (5) well-developed inner metatarsal tubercle (IMTL/FOL 0.13–0.19); (6) indistinct outer metatarsal tubercle; (7) second finger slightly to distinctly longer than fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin rough to rugose with longitudinal rows of tubercles; (10) presence of pronounced, pointed chin barbels; (11) absence of pronounced superciliary spines; (12) absence of inguinal ocelli or spots; (13) absence of distinctive markings along the posterior thigh; (14) broad but not fortified skull, without expansion of squamosal, maxilla, or posterior process of angulosplenial; and (15) clavicles absent.

Rhombophryne maraoraosp. nov. is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘C’ at site 406, ‘T’ at site 459, and ‘T’ at site 500; in 16S3’, ‘A’ at site 1057, ‘A’ at site 1075, and ‘A’ at site 1092.

Within the genus Rhombophryne, R. maraoraosp. nov. can easily be distinguished from all other species except R. testudo, R. coudreaui, and R. matavy by its rotund body and short, broad head. Among these species, it can be distinguished from R. testudo by smaller body size (SVL 22.5–28.9 mm vs 33.0–43.1 mm), longer head (HW/HL 1.69–1.88 vs 2.00–2.60), rougher skin, smaller chin barbels, and much less fortified skull; and from R. matavy by smaller body size (SVL 22.5–28.9 mm vs 40–50 mm), longer head (HW/HL 1.69–1.88 vs 1.88–2.05), presence of chin barbels (vs absence), and less fortified skull. Rhombophryne maraoraosp. nov. is most closely related to, and most similar to, R. coudreaui. These species are difficult to distinguish morphologically. The most reliable character for distinguishing these species is the presence of pronounced pointed barbels along the lower lip in R. maraoraosp. nov., versus fewer, less pronounced barbels in R. coudreaui. They may also differ in eye size, with R. coudreaui having larger relative eye size (ED/HL 0.29–0.31) than R. maraoraosp. nov. (ED/HL 0.25–0.27); and in relative finger length, with the second finger at least slightly longer than the fourth in R. maraoraosp. nov., vs equal in length in R. coudreaui.

An adult male specimen in a moderately good state of preservation, though fairly soft (Figs 8, 9). An incision made along the right flank to check the sex. Testes distinct.

Body robust and rotund. Head wider than long (HW/HL 1.76). Eyes quite small (ED/HL 0.25), pupils large, round. Snout rounded in dorsal and lateral views. Canthus rostralis distinct, concave. Loreal region concave, oblique. Nostril closer to tip of snout than to eye, slightly protuberant. Tympanum indistinct, round, TDH/ED 0.594. Supratympanic fold moderately distinct, raised but tubercular and so uneven in height, forming a sigmoid curve from the line of the top of the eye straight over the tympanum, curving down behind the tympanum, and then posteriorly to the top of the arm. A row of five (right) or three (left) small superciliary spines above each eye, as well as small granules distributed over the top of the eye and head. A row or pronounced tubercles (barbels) along the lower lip. Tongue partly removed as a tissue sample. It was attached anteriorly, broad, and unlobed. Maxillary and vomerine teeth present, vomerine teeth present in two curving rows separated at the midline by a small gap. Choanae round, placed laterally in the roof of the mouth.

Forelimbs relatively short and thick, the upper arm hardly distinguishable from the body cavity (FARL/SVL 0.323). Fingers without webbing, all short, relative lengths 1 < 2 = 4 < 3 (Fig. 9). Finger subarticular tubercles distinct, round, whitish; inner metacarpal tubercle broad and flat, outer metacarpal/palmar tubercle distinct and round. Hind limb thick, tibiotarsal articulation reaching insertion of arm when adpressed anteriorly along the body. TIBL/SVL 0.304. Inner metatarsal tubercle present, large. Outer metatarsal tubercle faint. Toes not webbed; first toe distinctly reduced, toe lengths 1 < 2 < 5 < 3 < 4, fifth toe distinctly shorter than third; subarticular tubercles distinct, broad and round; toe tips not enlarged (Fig. 9).

After 25 years in preservative, the colouration of the specimen is largely faded. It is beige in base colour, with light brownish symmetrical markings. These border the back of the head region, the scapular region, and from the inguinal region to the posterior third of the back, forming a beige cross-like shape over the central dorsum. The legs too are beige above with faint light brown crossbands on the thigh, more distinct crossbands on the shank, and a dark posterior tarsus. The hidden surfaces of the thighs are whitish, but there is a trapezoidal brown marking around the vent. The dorsal and lateral foot are beige with very fine brown specks. The ventral body has a beige base-colour, intensely speckled with brown (more distinct than above), especially over the chin and pectoral girdle. This pattern extends onto the ventral arms and legs. Colouration in life (Fig. 24D) was much browner than the specimen is in preservative. The outline of the markings on the dorsum in beige-cream was particularly distinctive.

SVL 22.5–28.9 mm (n = 3; a putative subadult, MRSN A2497, measures 20.9 mm, and the referred specimen with uncertain collection locality, MRSN A5524, measures 29.8 mm). For variation in measurements, see Table S5. All specimens have pronounced tubercles along the lower lip. Most individuals are a brownish cream colour dorsally in preservative, much lighter in colour than most R. coudreaui, but MRSN A5524 is much browner and more mottled, and the colour of this species in life is also dark brown (Fig. 24); differences in colour of the specimens may be due to preservation fluids or other factors, and are not taken to be diagnostic. The referred specimen BMNH 1987.331 is rather dark, but has also been stained to have blue-green bones, which may have altered its skin colour as well. Much of the body patterning is consistent, especially the dark suprascapular spots which define the short edge of a trapezoid where the eyes form the ends of the long edge. The sacral region also has dark markings, though less consistently than in R. coudreaui. In four of the five specimens (not MRSN 2497) the chin is marbled brown and cream. The first toe of MRSN A2496 is less distinctly reduced than other specimens, and is connected to the second toe with distinct webbing on the left side but not on the right. MRSN A5524 has a substantially larger relative inner metatarsal tubercle than the other individuals (IMTL/FOL 0.23 vs 0.13–0.19).

The call of this species is not known.

The Malagasy adjective maraorao meaning ‘rough to the touch’, in reference to the rugose skin of this species in life and in preservative. Used as an invariable noun in apposition.

Currently known from (1) Ambatoledama Corridor (Andasin’i Governera); (2) Amparihy, (3) Ambolokopatrika-Betaolana, and possibly (4) Anandrivola. Referral of material from Marojejy to this species remains too uncertain to include in its distribution at present. Elevation: ca 650–950 m a.s.l.

Rhombophryne maraoraosp. nov. is a fossorial species found in low- to mid-elevation humid forest; its ecology is poorly known, but presumably much like R. coudreaui. All of the individuals from Masoala and Ambolokopatrika-Betaolana were unearthed and collected whilst digging in the soil to install pitfall traps. The gut of MRSN A6929 contained a beetle, an amphipod, a small ant, pieces of an arthropod, and detritus (several leaf and bark fragments).

This species was listed as ‘Rhombophryne sp. Ca17’ by Belluardo et al. (2022), and ‘Rhombophryne sp. 17’ and ‘CCS “Sp. 17”’ by Carné and Vieites (2024).

The new species is placed in a clade containing R. mangabensis, R. savaka, and an undescribed candidate species (R. sp. Ca16) from the Andapa area for which only genetic data are known. It differs, however, from all nominal species of Rhombophryne by very high genetic divergences: 10.3% and 10.9% uncorrected p distance in the 16S3’ fragment from R. mangabensis and R. savaka, respectively; and >11% from all other species (Belluardo et al. 2022). It furthermore differs from R. mangabensis and R. savaka by the presence of reddish-orange colouration on the posterior thigh, and from the syntopic R. savaka by bioacoustic and further morphological characters (see Diagnosis below). In addition, it is phylogenetically sister to the R. mangabensis / R. savaka subclade (Belluardo et al. 2022) and thus cannot be considered conspecific with either of these species. Its status as distinct species is therefore beyond doubt.

ZSM 521/2016 (MSZC 0269), an adult male (call voucher), collected on 22 November 2016 in low elevation primary rainforest within Marojejy National Park (14.4400°S, 49.7782°E, 402 m a.s.l.), Sava Region, northeastern Madagascar, by M.D. Scherz, J.H. Razafindraibe, and A. Razafimanantsoa (Figs 8, 9, 26A–C, 28).

Three specimens: ZSM 517/2016 (ZCMV 15088), an unsexed adult, collected on the morning of 16 November 2016 at ‘Camp 0’ (ca 14.446°S, ca 49.785°E, ca 310 m a.s.l.), Marojejy National Park, Sava Region, northeastern Madagascar, by M.D. Scherz, M. Vences, A. Rakotoarison, M.C. Bletz, J.H. Razafindraibe, and A. Razafimanantsoa (Fig. 26D–G); ZSM 518/2016 (MSZC 0310), a juvenile, and UADBA-A-MSZC 0307 (Fig. 26H–K), an unsexed adult, both collected in the evening of the 26 November 2016 from the same locality as ZSM 517/2016, by M.D. Scherz, J.H. Razafindraibe, A. Razafimanantsoa, and C.R. Hutter.

The holotype is used as the reference specimen for this species in 16S rRNA barcoding (16S5’ OL780607; Belluardo et al. 2022). All paratypes conform well with the holotype in morphology, and are from near the type locality. Assignment of specimens ZSM 518/2016, ZSM 517/2016, and UADBA-A-MSZC 0307 is further confirmed by molecular taxonomic identification (Fig. 2). RAG1 sequence of this species is so far not available.

Within the R. testudo group, this species is most closely related to R. mangabensis, R. savaka, and its possible sister lineage R. sp. Ca16 based on molecular phylogenetic data (Fig. 2; Belluardo et al. 2022). It is characterised by the possession of the following unique suite of characters: (1) small body size, adult SVL 21.2–21.3 mm; (2) head wider than long (HW/HL 1.60–1.68); (3) moderately small eyes (ED/HL 0.36–0.38); (4) short hindlimbs (HIL/SVL 1.50–1.61); (5) small inner metatarsal tubercle (IMTL/FOL 0.12–0.13); (6) outer metatarsal tubercle absent; (7) second finger distinctly longer than fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin finely granular with a few scattered warts, especially a suprascapular pair outlined in black; (10) absence of chin barbels; (11) absence of pronounced superciliary spines; (12) absence of inguinal ocelli or spots; (13) presence of reddish orange in the inguinal region and on the posterior thigh; (14) unfortified skull without expansion of maxilla or posterior process of angulosplenial; (15) clavicles present, thin, curving; and (16) advertisement call (based on 16 analysed calls by one individual) tonal, with (17) call duration 231–262 ms, (18) inter-call interval 623–808 ms, and (19) dominant frequency 3178–3265 Hz.

Rhombophryne mavokelysp. nov. is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘A’ at site 315, ‘C’ at site 326, and ‘T’ at site 331; in 16S3’, ‘G’ at site 937, ‘G’ at site 938, and ‘A’ at site 956.

Within the genus Rhombophryne, R. mavokelysp. nov. can easily be distinguished from all species except R. ellae, R. ornata, and two other species described below (R. quentinisp. nov. and R. kotrobaratrasp. nov.), by the presence of reddish orange colouration on the posterior thigh. Among these species, it can be distinguished from R. ellae by a more dorsoventrally compressed habitus, smaller body size (SVL 21.2–21.3 mm vs 24.9 mm), wider head (HW/HL 1.60–1.68 vs 1.47), and shorter hindlimbs (HIL/SVL 1.50–1.61 vs 1.71); and from R. ornata by the absence of superciliary spines (vs presence). For distinction from R. quentinisp. nov. and R. kotrobaratrasp. nov., see the descriptions of those species, below. When the orange of the limbs is not visible there is also some resemblance to R. coudreaui and R. maraorao, which however differ by generally larger adult body size (SVL 21.5–28.9 vs 21.2–21.3 mm), much shorter hindlimbs (HIL/SVL 1.10–1.30 vs 1.50–1.61), and presence of chin barbels (vs absence).

Rhombophryne mavokelysp. nov. occurs syntopically or in near sympatry with the closely related R. savaka. Aside from colouration, R. mavokelysp. nov. can be distinguished from R. savaka by its rougher dorsal skin with more ridges (vs relatively smooth), and by the longer advertisement call duration (231–262 ms vs 121–142 ms), longer inter-call interval (623–808 ms vs 221–395 ms), and slightly lower dominant frequency (3178–3265 Hz vs 3714–3861 Hz).

A specimen in a good state of preservation (Fig. 8). A tissue sample was taken from its left thigh for genetic analysis.

Body rotund. Head wider than long (HW/HL 1.68). Eyes quite small (ED/HL 0.36), pupils small, round. Snout rounded in dorsal view, truncate in lateral view. Canthus rostralis distinct, concave. Loreal region concave, oblique. Nostril closer to tip of snout than to eye, slightly protuberant. Tympanum indistinct, round, TDH/ED 0.62. Supratympanic fold indistinct, demarcated at its anterior end by a dark comma-shaped marking. In life it was more distinct, curving from the posterior corner of the eye over the tympanum and towards the insertion of the arm (Fig. 26A). Superciliary spines absent, but two white dots above each eye. Small granules and ridges distributed over the body in life are largely flat in preservative but mostly still marked by a lighter colouration. Most prominent of these are a pair of markings in the suprascapular region, and a series of three (left) and two (right) bumps along the ilia and in the sacral region. Tongue broad, attached anteriorly, posteriorly free. Maxillary and vomerine teeth present, vomerine teeth present in two curving rows separated at the midline by a small gap. Choanae round, placed laterally in the roof of the mouth.

Forelimbs relatively short (FARL/SVL 0.417), fairly slender. Fingers without webbing, all short, relative lengths 1 < 4 < 2 < 3, second finger slightly longer than fourth (Fig. 9). Finger tips not expanded, slightly pointed. Finger subarticular tubercles indistinct, whitish; inner metacarpal tubercle broad and flat, outer metacarpal/palmar tubercle indistinct, greyish. Hind limb thick, tibiotarsal articulation reaching the eye when adpressed anteriorly along the body. TIBL/SVL 0.461. Inner metatarsal tubercle present, oblong, whitish. Outer metatarsal tubercle visible only as a slightly lightened area of the outer metatarsus. Toes not webbed; toes unreduced, toe lengths 1 < 2 < 5 < 3 < 4, fifth toe distinctly shorter than third; subarticular tubercles distinct, greyish, rather flat; toe tips slightly enlarged, slightly pointed (Fig. 9).

After seven years in preservative, the colouration of the specimen is quite vibrant, though lighter than in life (Fig. 8). The base colour is a soft pink, becoming more reddish posteriorly and mauve anteriorly, especially over the head. The dorsal surfaces of the eyes are dark mauve. There are several dark brown markings on the body, particularly the comma-shaped markings in the supratympanic region, the black spots with mauve centres on the suprascapular region and iliac/sacral region, and crossbands on the forelimbs. Additionally, the ventral surfaces of the feet, and especially the ventral portion of the posterior thigh are almost black. The darkened area of the thigh is not trapezoidal as in some other Rhombophryne species, but really extends over the entire length of the posterior thigh. It is separated from the dorsal colouration by areas that are cream in preservative. The dorsal surfaces of the legs have faint brown crossbands, two on the thigh, two on the shank, and two or three on the feet. The dorsal surface of the foot is laterally pinkish, but over most of its surface is mottled brown, with a light annulus before each toe tip. The dorsal surfaces of the hands are similar. The flank colouration merges seamlessly with the venter (i.e., there is no dorsolateral colour border, nor indeed a lateral head colour border). The ventral colouration is largely cream mottled with a greyish brown. The chin is darkest, with the posterior extent of the vocal sac clearly demarcated. The ventral arms are a light cream, less yellow than over the hind limbs. Colouration in life was like in preservative but generally more orange.

SVL 21.2–21.3 mm (n = 2). For variation in other measurements, see Table S5. Morphology is highly consistent. All specimens collected were characterised by highly similar colouration and patterning, except that in ZSM 517/2016 the posterior thigh is bright pink where it is cream in ZSM 521/2016, the thigh is more clearly striated, and the dark colouration around the cloaca is more restricted in distribution. All known specimens possess a dark suprascapular spot with a light middle, and a dark, almost comma-shaped marking in the supratympanic region (Figs 26, 27), similar to R. mangabensis (Fig. 18), and distinct from R. savaka (Fig. 21).

The holotype (ZSM 521/2016) was collected after recording a call in primary low-altitude rainforest, under leaf litter, during dry weather. It was not seen calling, but was collected from the location of the call emission, and the call is similar to but distinctly different from that of R. savaka, and we are therefore confident that it is assignable to this species and this individual. The advertisement call, recorded on 23 November 2016 (20:20 h) at an unknown air temperature, consists of a tonal note of moderate duration emitted in regular call series (Fig. 29). Each call exhibits some amplitude modulation with a very short intermittent drop in energy occurring after about one third of the call’s duration. This drop in energy is also visible in the audiospectrogram, with frequencies slightly being shifted in the last two thirds of the call’s duration when compared to the first third and showing a somewhat different structure of harmonics. Overall, slight upward frequency modulation is evident within each call, with a short terminal drop. Numerical parameters of one complete call series and 16 analysed calls are as follows: call duration (= note duration) 231–262 ms (245 ± 8 ms); inter-call intervals within regular call series 623–808 ms (701 ± 59 ms); number of calls per call series 14; duration of regular call series 12,583 ms; dominant frequency 3178–3265 Hz (3219 ± 28 Hz); prevalent bandwidth 1500–8400 Hz; frequency bands in the first third of the call recognizable at approximately 2050, 3100, 4200, 5200 and 6140 Hz, in the last two thirds of the call at approximately 1650, 3250, 4800, 6400, and 8100 Hz.

The Malagasy adjective mavokely meaning ‘pink’, in reference to the pinkish colouration of this species in life and in preservative, especially on the legs. ‘Mavokely’ is also a linguistic quirk of the Malagasy language, as it is derived from the juxtaposition of the components mavo meaning ‘yellow, and kely meaning ‘small’. This name thus forms a double entendre, by referring also to the small stature and yellowish colouration of some individuals in life. Used as an invariable noun in apposition.

This species is currently definitively known only from (1) Marojejy National Park (type locality). However, photographs of specimens tentatively referrable to this species from (2) Anjanaharibe-Sud (14.72°S, 49.46°E, ca 1430 m a.s.l.) and (3) Simpona Lodge in Makira Natural Park (near 15.1992°S, 49.6208°E, ca 410 m a.s.l.) have been sent to us by Éric Mathieu and Lucas Pasteur, respectively (Fig. 27), suggesting that it may have a somewhat larger distribution in the rainforests of northeastern Madagascar. Elevation: ca 310–402 m a.s.l., but the record from Anjanaharibe-Sud would add ca 1000 m elevation to ca 1430 m a.s.l., if verified.

Rhombophryne mavokely is a semi-fossorial or detriticolous species found in low- to mid-elevation humid forest. All specimens were found in the leaf litter, and this species probably spends most of its life in the interstitial layer between the surface of the leaflitter and the soil. ZSM 517/2016 was collected less than a metre from a curled-up snake, Alluaudina bellyi, which is likely to prey upon this and other leaf-litter dwelling frog species (Hutter et al. 2018). We found Rhombophryne mavokelysp. nov. at consistently lower elevation than R. savaka, but it is not clear if there is a contact zone between the two species at around 400–450 m a.s.l., and records from higher elevations mentioned above remain to be verified.

This candidate species was identified by Belluardo et al. (2022) based exclusively on GenBank sequences of the specimen AMNH A181903 (RAX 10368), a specimen registered as ‘Rhombophryne cf. minuta’ on the AMNH online database portal (https://emu-prod.amnh.org, accessed 25 January 2023). It was referred to as ‘Rhombophryne sp. 16’ by Belluardo et al. (2022) and ‘UCS “Sp. CA16”’ by Carné and Vieites (2024). It has been sequenced for mitochondrial markers 16S3’ and 16S5’ (KM509192), COI (KM509860), and nuclear genes BDNF (KM509332), TYR (KM509984), SIAH1 (KM509728), and C-MYC (KM509466). It was collected in the Andapa area (given as a county in the AMNH online database, without precise coordinates) of the Sava Region, northeastern Madagascar by C.J. Raxworthy. Based on its phylogenetic position (Fig. 2; Belluardo et al. 2022), it appears to be a member of the R. mangabensis species complex, but we have not been able to examine this specimen, and therefore are not able to assess it taxonomically. Genetically, it differs by >7.95% uncorrected p distance in the 16S3’ fragment from all other Rhombophryne species (Table S2). It is distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘A’ at site 293, ‘G’ at site 483, and ‘A’ at site 539. No diagnostic sites were identified for 16S3’.

The sphenethmoid varies from fully ossified and covering the entire wall of the braincase (R. testudo, R. matavy, R. maraoraosp. nov.), to strongly ossified and covering most of the wall of the braincase (R. coudreaui, R. mangabensis, R. savaka), to strongly ossified but only covering the anterior half of the wall of the braincase (R. mavokelysp. nov.).

The exoccipital is surprisingly weakly ossified in the otherwise hyperossified skull of R. testudo. It is ossified in R. savaka, R. mangabensis, and R. matavy, but not the other species (but this is not a diagnostic feature, as ossification in this bone varies within species). The occipital condyles are enlarged in R. testudo and R. matavy. The exoccipitals do not meet medially. The prootic is well ossified in all species.

The septomaxilla is strongly reduced in R. testudo to a diminutive element lacking the medial ramus (and apparently unossified on the right side, see Fig. 11D). The medial ramus is apparently also missing from R. maraoraosp. nov., R. mangabensis, and R. coudreaui, but it is present in R. matavy; however, see our previous comments on the septomaxilla and its ossification, and why it should not be relied upon as a diagnostic feature in micro-CT scans (Scherz et al. 2017a).

The columella is rather similar in shape and structure among species. It nearly touches the otic ramus of the squamosal in R. testudo.

Ventral investing and palatal bones. The cultriform process of the parasphenoid is extremely broad in R. testudo and R. matavy, broad in R. coudreaui and R. maraoraosp. nov., and not expanded in R. mavokelysp. nov., R. mangabensis, and R. savaka.

The anterior portion of the vomer is triradiate, nearly crescentic in some species. The posterior portion is generally sigmoid, but rather straight in R. testudo and R. matavy. It bears distinct teeth in all species except R. testudo, where there are strong, bumpy ventral ridges. There is a distinct diastema in the vomerine teeth of R. savaka, R. mavokelysp. nov., and R. coudreaui, and a small gap that may be a diastema in R. mangabensis. The neopalatine, which lies dorsally on top of the vomer, is distally expanded in R. testudo and R. matavy.

Maxillary arcade. Maxillary teeth are present in all species except R. testudo. The premaxilla is small in R. testudo. The maxilla itself is extremely deep in R. testudo, much more so than any other species. The facial process of maxilla is bluntly (R. coudreaui, R. mangabensis, R. maraoraosp. nov., R. mavokelysp. nov., R. savaka, R. mangabensis), or sharply and triangularly (R. matavy, R. testudo) raised, in R. testudo in broad dorsal contact with the maxillary process of the nasal (closely approaching in R. matavy, not in contact in any other species). The contact with the quadratojugal is extremely fortified in R. testudo, and is strong in all other species.

Suspensorium. The anterior ramus of the quadratojugal in R. savaka and R. mavokelysp. nov. has a concave ventral edge in lateral view; it is rather straight in the other species, except R. testudo, where it is highly unusual in shape, curving ventrally, in the opposite direction to its normal curve in lateral perspective (Fig. 11G). The quadratojugal-squamosal contact in R. testudo is nearly the full length of the bone; in the other species, it is brief and posterior.

The squamosal is ventrally hugely fortified in R. testudo and to a lesser degree in R. matavy, with a strongly expanded ventral ramus. The otic and zygomatic rami form a scooped structure in dorsal view in all species of this group. The zygomatic ramus is longer than the otic in R. testudo, but they are more or less the same length in the other taxa. In all species, the otic ramus ascends and flattens dorsoventrally. It is flat ended in R. testudo, but bluntly rounded in all other species.

The pterygoid is likewise extraordinary in R. testudo, with a massively expanded posterior ramus and expanded medial ramus. The medial ramus is exceptionally long in R. matavy.

Mandible. The mentomeckelians of R. testudo are at an almost right-angle to their normal position, forming essentially blunt caps for the angulosplenials. They are ‘normal’, hourglass-shaped small elements forming the mandibular symphysis medially in all other species. The dentary is either totally reduced or short and thin in R. testudo. It is poorly ossified in R. maraoraosp. nov. and R. matavy.

The angulosplenial is posteriorly strongly expanded in R. testudo, with a deep posterolateral facet that gives it a rather unusual shape. The coronoid process is strongly raised in that species. The coronoid process of R. mavokelysp. nov. is more strongly raised than that of R. savaka or R. mangabensis. The posterior process (articular facet) is moderately expanded in all species except R. testudo, where it is strongly expanded.

Pectoral girdle. The coracoids of R. testudo and R. matavy have a long medial contact facet (unossified), much longer than other members of the species group. Clavicles are present and curved in R. mavokelysp. nov. and R. savaka, reduced (or poorly ossified) in R. mangabensis, but absent in all other species. The scapula and cleithra do not differ sufficiently for further comment.

The humeral crests are strongly developed in all species, though to the greatest extent in R. testudo. The crista ventralis is strong, extending one third (R. mavokelysp. nov.), around half (R. savaka, R. maraoraosp. nov., R. mangabensis), or over half (R. testudo, R. coudreaui, R. matavy) the length of the bone. The crista lateralis is particularly strong in R. testudo and R. matavy. The radioulna varies in dimensions, but not substantially in structure among species.

Carpals 2, 3–5, element Y, radiale and ulnare present. Howes and Ridewood (1888) asserted that the carpus of Rhombophryne testudo has carpal 2 fused into the joint 3–5 element of most other frogs, but we do not find this to be the case. However, R. coudreaui does not seem to have a carpal 2 (Fig. 14I), so it may be that Howes and Ridewood (1888) were examining bones of that species. The carpal elements of the examined specimen of R. maraoraosp. nov. were not sufficiently ossified to study the bones of the hands (Fig. 25I). The prepollex of R. savaka, R. mangabensis, R. testudo, R. matavy, and R. coudreaui is large and subtriangular. The digital formula of all species is the same (2-2-3-3), and terminal phalanges consistently end with small knobs.

Vertebral column. Transverse processes of V2 perpendicular to body axis in all species except R. savaka, where they are angled anteriorly. All transverse processes long, much longer than the centra are wide in all species except R. mangabensis, R. savaka, and R. maraoraosp. nov., where the posterior four presacrals have transverse processes slightly shorter than the centrum is wide. The sacrum is as wide as V4 in all species, its anterior edge straight, angled either slightly anteriorly (R. savaka) or posteriorly (all other species). The diapophyses are not strongly flared, and the posterior edge is at most slightly curved. The urostyle has a dorsal ridge along its entire length in R. testudo and R. maraoraosp. nov., but the posterior quarter is free in all other species.

Iliac shafts with strong dorsal crests in all species except R. mavokelysp. nov. and R. savaka. The oblique groove is practically absent and dorsal prominence absent in all species except R. matavy, where there is a distinct dorsal prominence and corresponding oblique groove, and R. mangabensis, where an oblique groove is recognisable, but there is no dorsal prominence. The femur has a slight posterior ridge in all species except R. savaka, R. mavokelysp. nov., and R. mangabensis. The tibiofibula and tarsus do not bear further comment. The toe formula is standard (2-2-3-4-3). The prehallux of R. testudo and R. matavy is a dramatically expanded single element. In R. savaka, R. mangabensis, and R. coudreaui it is comprised of two elements. The state in R. maraoraosp. nov. and R. mavokelysp. nov. cannot be commented upon because of the low ossification. Terminal phalanges of all toes short and knobbed.

Type species of Mantiphrys Mocquard, 1895. Parker (1934) considered R. laevipes to be a synonym of Mantipus hildebrandti Peters, 1883, and it was, in essence, described as such by Mocquard; the description given is of a specimen assigned to M. hildebrandti, but in a footnote Mocquard notes the numerous points of difference from Peters’ description, and states that, if Peters’ description is found to be accurate, then he would propose to name the new form Mantiphrys laevipes (Mocquard 1895). The name was resurrected by Guibé (1946). Today, Mantipus hildebrandti is considered a junior synonym of Plethodontohyla inguinalis Boulenger, 1882. We have verified this based on re-examination of the holotype of M. hildebrandti, ZMB 10440, which was reported lost by Glaw and Vences (1992) but was rediscovered by Bauer et al. (1996).

Some specimens formerly thought to be juveniles of this species have been reidentified in this study as R. ellae.

MNHN 1893.285, an adult male, collected on an unknown date on ‘Montagne d’Ambre’, Diana Region, northern Madagascar by Mr Alluaud and Mr Belly (Figs 30, 31, 34).

None.

ZSM 902/2003 (FGMV 2002.0916), a juvenile specimen, collected on 19 February 2003, and ZSM 925/2003 (FGMV 2002.0998), an adult female, collected on 19–20 February 2003 on Montagne d’Ambre (no precise coordinates), Diana Region, northern Madagascar, by F. Glaw, R.D. Randrianiaina, and A. Razafimanantsoa; ZSM 200/2004 (FGZC 387) and ZSM 218/2004 (FGZC 423), a juvenile and an unsexed individual, collected on 19 February 2004 on the Voie des Milles Arbres (12.5200°S, 49.1756°E, 1052 m a.s.l.), Montagne d’Ambre National Park, Diana Region, northern Madagascar, by F. Glaw, M. Puente, R. Randrianiaina, A. Razafimanantsoa; ZSM 2188/2007 (FGZC 1283), a juvenile, collected on 13 March 2007 near the Cascade Antakarana (ca 12.52°S, 49.17°E, ca 1030 m a.s.l.), Montagne d’Ambre National Park, Diana Region, northern Madagascar, by P. Bora; ZSM 77/2018 (MSZC 0648), adult male (call voucher), collected at 14:56 h on 19 November 2017 near the Gîte d’Étape (12.5204°S, 49.1718°E, 1066 m a.s.l.), Montagne d’Ambre National Park, Diana Region, northern Madagascar, by M.D. Scherz, J.H. Razafindraibe, A. Razafimanantsoa, O. Randriamalala, S.M. Rasolonjavato, R. Tiavina, and A. Rakotoarison (Fig. 32A–C, 33A–C); UADBA-A 62340 (MSZC 0526), a subadult, collected at night on 25 December 2017 at 12.5205°S, 49.1890°E, 1028 m a.s.l. in Montagne d’Ambre National Park, Diana Region, northern Madagascar, by M.D. Scherz, J.H. Razafindraibe, A. Razafimanantsoa, O. Randriamalala, S.M. Rasolonjavato, R. Tiavina, and A. Rakotoarison (Fig. 32D–F); UADBA-A 62493 (MSZC 0654), a juvenile, collected on 19 November 2017 at 12.5206°S, 49.1862°E, 1008 m a.s.l. in Montagne d’Ambre National Park, Diana Region, northern Madagascar, by M.D. Scherz, J.H. Razafindraibe, A. Razafimanantsoa, O. Randriamalala, S.M. Rasolonjavato, R. Tiavina, and A. Rakotoarison (Fig. 32G–I); UADBA-A-FGZC 1052, individual of unknown sex or maturity, collected on 25 February 2007 on Montagne d’Ambre in a pitfall trap (precise coordinates not available), Diana Region, northern Madagascar, by F. Glaw, P. Bora, H. Enting, J. Köhler, and I. Knoll.

The specimen ZSM 853/2003 (FGMV 2002.823), an adult female, collected on 3 February 2003 at ‘Camp 1’ (13.9770°S, 48.4220°E, 751 m a.s.l.), Manongarivo Massif, Diana Region, northern Madagascar, by F. Glaw, R.D. Randrianiaina, and M. Vences (Fig. 33H–I), is phylogenetically sister to all other specimens collected so far (Fig. 2), and differs genetically from all other specimens of R. laevipes by 1.24–2.46% in the 16S3’ marker, and 4.90–5.45% in the 16S5’ marker, but is consistently recovered as conspecific in species delimitation, and is therefore assigned to this species. A second specimen from the other side of this mountain, BMNH 1987.2300, an unsexed adult, collected on 25 February 1988 at ‘Camp B’ (14.067°S, 48.283°E, 350 m a.s.l.), Manongarivo Massif, Sofia Region, northern Madagascar, by C.J. Raxworthy, agrees morphologically, and is consequently also assigned to this species.

ZSM 218/2004 is used as the reference specimen for this species in 16S rRNA barcoding (16S3’ and 16S5’ EU341104; Vieites et al. 2009) and COI barcoding (COIKF611587; Perl et al. 2014). All of the referred material except ZSM 853/2003 is collected at the general type locality. The adult specimens conform with the holotype in overall morphology, and especially in the presence of white spots on the hidden surfaces of the legs. Assignment of UADBA-A-FGZC 1052 (not examined morphologically), UADBA-A 62340 (MSZC 0526), UADBA-A 62493 (MSZC 0654), ZSM 77/2018, and ZSM 853/2003 is further confirmed by molecular taxonomic identification (Fig. 2). ZSM 77/2018 has been sequenced with the FrogCap hybrid capture probe set and is included in the RAG1 haplotype network (Fig. 4).

Within the R. laevipes group, this species has a rather isolated position, and is probably sister to a subclade containing various other species based on molecular phylogenetic data (Fig. 2; Belluardo et al. 2022). It is characterised by the possession of the following unique suite of characters: (1) large body size, adult SVL 42.8–50.8 mm; (2) head wider than long (HW/HL 1.57–1.84); (3) moderately small eyes (ED/HL 0.30–0.34); (4) relatively long hindlimbs (HIL/SVL 1.62–1.86); (5) small inner metatarsal tubercle (IMTL/FOL 0.08–0.11); (6) outer metatarsal tubercle absent; (7) second finger shorter than or equal in length to fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin smooth with very few raised bumps in some individuals; (10) absence of chin barbels; (11) absence of pronounced superciliary spines; (12) presence of white inguinal spots on a dark brown background; (13) presence of white spots on the posterior thigh and ventral surface of the shanks; (14) unfortified skull without expansion of maxilla or posterior process of angulosplenial; (15) clavicles present, thin, curving; and (16) advertisement call (based on 12 analysed calls by one individual) highly pulsed, with (17) call duration 208–254 ms, (18) inter-call interval 1563–2186 ms, and (19) dominant frequency 612–631 Hz.

Rhombophryne laevipes is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘T’ at site 354, ‘G’ at site 395, and ‘C’ at site 611; in 16S3’, ‘G’ at site 1075, ‘T’ at site 1086, and ‘G’ at site 1165.

Within the genus Rhombophryne, R. laevipes can easily be distinguished from R. testudo, R. coudreaui, R. matavy, and R. maraoraosp. nov. by smooth skin (vs rough), absence of chin barbels (vs presence), much longer hindlimbs (HIL/SVL 1.62–1.86 vs 1.10–1.41), and presence of white spots in the inguinal region and on the ventral shank (vs absence); from R. mangabensis, R. mavokelysp. nov., R. savaka, R. proportionalis, and members of the R. ellae and R. minuta species groups by much larger adult body size (SVL 42.8–50.8 mm vs 11.0–30.1 mm), and presence of white spots in the inguinal region and on the ventral shank (vs absence); and from all members of the R. serratopalpebrosa species group by the absence of superciliary spines (vs presence), and presence of white spots in the inguinal region and on the ventral shank (vs absence).

Within the R. laevipes species group, R. laevipes may not be distinguishable from R. nilevina morphologically (traits formerly thought to be diagnostic of the latter species are now known to be variable and overlap with R. laevipes; see the account, below), but can be distinguished by its shorter advertisement call (call duration 208–254 ms vs 526–534 ms), much shorter inter-call interval (1.5–2.2 s vs 42–126 s), and higher dominant frequency (612–631 Hz vs 526–534 Hz). It can be distinguished from R. botabota by the presence of white spots on the inguinal region, posterior thigh, and ventral shank (vs black inguinal ocelli or absence of inguinal spots, and no remarkable colour on the hindlimbs), and pulsed (vs tonal) advertisement call that is longer (call duration 208–254 ms vs 161–201 ms) and lower in dominant frequency (612–631 Hz vs 1256–1291 Hz). For distinction from newly described members of this species group, see their respective descriptions below.

An adult male specimen in a good state of preservation, though strongly faded (Figs 30, 31). An L-shaped incision made in the dorsal skin, a further such incision made over the pectoral girdle to expose the pectoral girdle, and a straight incision along the right flank. The rictus is ripped on both sides, and a small pinhole through the middle of the chin.

Body robust. Head wider than long (HW/HL 1.62). Eyes quite large (ED/HL 0.31), pupils large, round. Snout rounded in dorsal and lateral view. Canthus rostralis distinct, concave. Loreal region concave, oblique. Nostril closer to tip of snout than to eye, slightly protuberant. Tympanum distinct, oval, TDH/ED 0.57. Supratympanic fold distinct, strongly raised, running straight from posterior corner of eye over tympanum, curving ventrally posterior to the tympanum towards the insertion of the arm. Superciliary spines absent. Dorsal skin smooth. Ventral skin very finely granular. Tongue broad, attached anteriorly, posteriorly free. Maxillary and vomerine teeth present, varying in height, separated at the midline by a small gap. Choanae ovoid, placed laterally in the roof of the mouth.

Forelimbs relatively long (FARL/SVL 0.403), strongly built. Fingers without webbing, moderately long, relative lengths 1 < 2 < 4 < 3, second finger slightly shorter than fourth. Finger tips not expanded, rounded. Finger subarticular tubercles distinct, whitish, flat; inner metacarpal tubercle broad and flat, outer metacarpal/palmar tubercle indistinct. Hind limb strong, tibiotarsal articulation reaching tympanum when adpressed anteriorly along the body. TIBL/SVL 0.524. Inner metatarsal tubercle present, oblong, somewhat bulging. Outer metatarsal tubercle absent. Toes not webbed; toes unreduced, toe lengths 1 < 2 < 5 < 3 < 4, fifth toe distinctly shorter than third; subarticular tubercles distinct, slightly raised; toe tips not enlarged, rounded.

After at least 128 years in preservative, the colouration of the specimen is largely lost and the skin rather translucent, especially ventrally. The only traces of colouration that remain are on the legs: The posterior thighs are dark brown with several large white spots on the ‘hidden’ areas (not symmetrical). The left shank and foot are dark brown dorsally, and ventrally the shanks are also dark brown with round whitish spots. Colouration in life unknown.

SVL 42.8–50.8 mm (n = 5). For variation in other measurements, see Table S6. A dark brown chevron is often present over the scapular region (Figs 32, 33), and the side of the head is usually dark brown below the supratympanic fold, but lighter brown ventrally along the mouth and rictus (Figs 32A, 32D, 32G, 33A, 33D, 33F, 33H). The inguinal region is dark brown with white spots, and the posterior thigh (e.g., Fig. 33A, B, F, H) and ventral shank also have distinctive white or orange spots. These are present also in juveniles (e.g., Fig. 32I). The dorsal colouration can be highly reticulated dark patterns (e.g., Fig. 33G, H), or just scattered dark spots (e.g., Fig. 33F). The ventral abdomen is highly variable, usually with numerous dark spots, and large unpigmented areas (Figs 32C, 32F, 32I, 33E, 33I). The dorsal thigh and shank showed dark brown crossbands in all adult specimens we examined, but these were only very weakly visible in the juvenile UADBA-A 62493 (MSZC 0654) (Fig. 32G–I). Juveniles and subadults tend to be quite orange in colour (Fig. 32D–I, see also image captioned ‘Rhombophryne sp., Montagne d’Ambre’ on page 448 of Glaw and Vences 2007), often with an X-shaped marking (which can be indistinct, cf. Fig. 32I) on the dorsum. The areas that lack dark colouration appear to correspond to those that appear white in adults. Round spots on the ventral shank are less distinct in juveniles, and apparently become more distinct with age (Fig. 32). The dark colouration of the lateral head is always present.

The advertisement call recorded on 19 November 2017 (14:30 h) near the Gîte d’Étape (air temperature 21.3 °C; voucher specimen ZSM 77/2018, MSZC 0648) consists of a low-pitched, pulsed note of moderate duration, usually emitted in short call series containing 2 or 3 calls, although one single call was also recorded (Fig. 35). Calls (= notes) exhibit distinct amplitude modulation, with call energy starting at low level, rapidly increasing after about a fifth of the call’s duration, reaching its maximum at about half of the call’s duration, followed by a decrease towards the call’s end. Pulses are very narrowly spaced and very short in duration, with each pulse apparently shorter than 3 ms, but difficult to measure exactly. It is also not possible to count the number of pulses per note (= call), but pulse repetition rate can roughly be calculated in major parts of the note. Numerical parameters of 12 analysed calls are as follows: call duration (= note duration) 208–254 ms (228 ± 13 ms); inter-call intervals within regular call series 1563–2186 ms (1758 ± 231 ms); number of calls per call series 2 or 3 (2.1 ± 0.3); duration of regular call series 2008–4167 ms (2632 ± 899 ms); pulse repetition rate within calls about 310–320 pulses/second; dominant frequency 612–631 Hz (619 ± 6 Hz); prevalent bandwidth 320–3000 Hz; numerous parallel frequency bands recognizable with approximately 320 Hz spacing up to 9200 Hz, which represent a reflection of pulse rate (see Köhler et al. 2017).

Latin feminine nominative singular adjective derived from the words ‘laevis’, meaning smooth or slippery, and ‘pes’ meaning ‘foot’.

This species is known from mid-elevation rainforests of (1) Montagne d’Ambre National Park (type locality). In an intensive survey on Montagne d’Ambre in 2017 and 2018, we did not find it above 1100 m a.s.l. on this mountain, nor did we find it below 900 m a.s.l. This matches observations by Raxworthy and Nussbaum (1994), who recorded this species to occur 900–1200 m a.s.l. Additionally, we here confirm its occurrence (2) on the Manongarivo Massif (at 350–751 m a.s.l.). Elevation: 350–1200 m a.s.l.

Rhombophryne laevipes is a semi-fossorial or detriticolous species found in low- to mid-elevation humid forest. Males call during and shortly after rain, especially at night, from concealed positions within the leaf litter. Between November 2017 and January 2018, calling activity was greatest at the start of November, and diminished as rain frequency increased. This suggests that mating may take place at the start of the rainy season. When handled, captured males that had been calling struggled to deflate their vocal sacs, and emitted distress calls. Juvenile and subadult individuals were more commonly encountered than adults, usually active at night. After capture, we spent a short time observing the behaviour of ZSM 77/2018. Its initial escape attempts were long leaps. After calming down, when placed in leaf litter, it did not attempt to dig backwards, as is thought to be the dominant mode of digging in Rhombophryne. Instead, it attempted to hide by pushing itself under objects head-first, using its strong hindlimbs to push its body forward (Fig. 33C). Eudeline et al. (2015) reported on the predation of this species by Compsophis albiventris.

This species was listed as ‘Rhombophryne sp. 1’ by Wollenberg et al. (2008), ‘Rhombophryne sp. 2’ by Vieites et al. (2009), and ‘Rhombophryne sp. Ca2’ by Perl et al. (2014). Carné and Vieites (2024) treated specimens from Makira as ‘DCL “Makira”’.

ZSM 358/2005 (FGZC 2896), an adult male, collected on 18 February 2005 at ‘Camp Simpona’ (14.4364°S, 49.7433°E, 1326 m a.s.l.), Marojejy National Park, Sava Region, northeastern Madagascar, by F. Glaw, M. Vences, and R.D. Randrianiaina (Figs 30, 31, 37).

Six specimens: ZSM 538/2009 (ZCMV 11473), ZSM 539/2009 (ZCMV 11474), two presumably immature males, collected on 21 June 2009 at ‘Camp 1’ Angozongahy, (15.4370°S, 49.1186°E, 1009 m a.s.l.), western side of the Makira Plateau, Analanjirofo Region, northeastern Madagascar, by M. Vences, D.R. Vieites, F. Ratsoavina, R. Randrianiaina, E. Rajeriarison, T. Rajofiarison, and J. Patton; MRSN A2956 (FN 7164), MRSN A2640 (FN 7238), MRSN A2954 (FN 7281), MRSN A2955 (FN 7300), two males and two females, collected on 9–15 December 1997 at ‘Camp 2’ Andranomadio (14.5304°S, 49.4383°E, 860 m a.s.l.), Ambolokopatrika-Betaolana Forest, Sava Region, northeastern Madagascar, by F. Andreone, G. Aprea, and J.E. Randrianirina.

UADBA-A-ZCMV 15158 (Fig. 36L–N), ZSM 515/2016 (ZCMV 15241; Fig. 36J, K), and ZSM 513/2016 (ZCMV 15159; Fig. 36O–Q), three juveniles, and ZSM 514/2016 (ZCMV 15160; Fig. 36D–F), ZSM 523/2016 (ZCMV 15216; Fig. 36G–I), and ZSM 524/2016 (ZCMV 15279; Fig. 36A–C), three unsexed adults, all collected on 18–20 November 2016 in the vicinity of ‘Camp Simpona’ (ca 14.4366°S, 49.7434°E, 1325 m a.s.l.), Marojejy National Park, Sava Region, northeastern Madagascar, by M.D. Scherz, A. Rakotoarison, M. Bletz, M. Vences, J. Razafindraibe, and A. Razafimanantsoa; MNCN-uncatalogued (DRV 5836), an unsexed individual, collected on 25 June 2009 at ‘Camp 1’ Angozongahy, (15.4370°S, 49.1186° E, 1009 m a.s.l.), western side of the Makira Plateau, Analanjirofo Region, northeastern Madagascar, by M. Vences, D.R. Vieites, F. Ratsoavina, R. Randrianiaina, E. Rajeriarison, T. Rajofiarison, and J. Patton.

The holotype is used as the reference specimen for this species in 16S rRNA barcoding (16S3’ EU341102/FJ559297; 16S 5’ EU341102; Vieites et al. 2009) and COI barcoding (COIKF611585; Perl et al. 2014). All paratypes and referred specimens conform well with the holotype in morphology. MRSN A2640, MRSN A2956, ZSM 513/2016, ZSM 514/2016, ZSM 515/2016, ZSM 524/2016, ZSM 538/2009, ZSM 539/2009, MNCN-DRV 5836, and UADBA-A-ZCMV 15158 are further confirmed by molecular taxonomic identification (Fig. 2). MRSN A2956 is present in the RAG1 haplotype network (Fig. 4).

Within the R. laevipes group, this species appears to be sister to a clade consisting of R. sonaliaesp. nov. and R. anatialasp. nov. (described below) based on molecular phylogenetic data (Fig. 2; Belluardo et al. 2022). It is characterised by the possession of the following unique suite of characters: (1) medium body size, adult SVL 24.2–32.2 mm; (2) head wider than long (HW/HL 1.44–1.69); (3) moderately small eyes (ED/HL 0.33–0.38); (4) moderately long hindlimbs (HIL/SVL 1.41–1.75); (5) small inner metatarsal tubercle (IMTL/FOL 0.08–0.13); (6) outer metatarsal tubercle absent; (7) second finger shorter than or equal in length to fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin smooth; (10) absence of chin barbels; (11) absence of pronounced superciliary spines; (12) absence of distinct inguinal spots (sometimes dark brown lines converging anterodorsally); (13) absence of distinctive markings along the posterior thigh; (14) unfortified skull without expansion of maxilla or posterior process of angulosplenial; (15) clavicles present, thin, curving; and (16) advertisement call (based on 4 analysed calls by one individual) tonal, with (17) call duration 161–201 ms, (18) inter-call interval 2529–2716 ms, and (19) dominant frequency 1256–1291 Hz.

Rhombophryne botabota is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘G’ at site 304, ‘T’ at site 568, and ‘A’ at site 682. No diagnostic sites were identified for 16S3’.

Within the genus Rhombophryne, R. botabota can easily be distinguished from R. testudo, R. coudreaui, R. matavy, and R. maraoraosp. nov. by smooth skin (vs rough), absence of chin barbels (vs general presence), longer hindlimbs (HIL/SVL 1.41–1.75 vs 1.10–1.41); from R. mangabensis by larger body size (SVL 24.2–32.2 mm vs 19.6–23.2 mm), and smooth skin (vs finely granular with scattered warts); from R. savaka by larger body size (SVL 24.2–32.2 mm vs 18.8–20.9 mm), absence of a diastema in the vomerine teeth (vs presence), and absence of inguinal spots (vs occasional presence); from R. mavokelysp. nov., R. ornata, and members of the R. ellae species group by the absence of reddish orange colouration on the posterior thigh and in the inguinal region (vs presence); from members of the R. minuta species group by generally shorter hindlimb length (HIL/SVL 1.41–1.75 vs 1.73–1.84), and less gracile habitus; from R. proportionalis by much larger adult body size (SVL 24.2–32.2 mm vs 11.0–12.3 mm); and from all members of the R. serratopalpebrosa species group by the absence of superciliary spines (vs presence).

Within the R. laevipes species group, see the account of R. laevipes above for distinction from that species. Rhombophryne botabota can be distinguished from R. nilevina by smaller body size (SVL 24.2–32.2 mm vs 41.2–57.2 mm), absence of white spots in the inguinal region and on the posterior thigh and ventral shank (vs sometimes present), and tonal (vs pulsed) advertisement call that is shorter (call duration 161–201 ms vs 538–598 ms) and higher in dominant frequency (1256–1291 Hz vs 526–534 Hz). For distinction from newly described members of this species group, see their respective descriptions below.

SVL ranges from 24.2–32.2 mm; for variation in other measurements, see Table S6. Skin texture of the newly collected material was surprisingly variable in life, ranging from smooth to tubercular (Fig. 36). The supratympanic fold was consistently highly pronounced and always dark in colour. Colouration was noted to vary substantially in the type series by Scherz et al. (2016a), most importantly including the occasional presence of spots on the posterior thigh, and presence of a dark inguinal ‘stripe’ in almost all individuals. Many also possessed a pair of dark spots on top of the head behind the eyes (Fig. 36J, M, P).

The allocation of the analysed recording to R. botabota is slightly tentative, as the recorded individual was not seen calling. However, R. botabota was the only Rhombophryne species found at the place of call emission (see Scherz et al. 2016a). The advertisement call recorded on 24 June 2009 (12:00 h) at Angozongahy site, Makira (estimated air temperature 22–24 °C), consists of a single tonal note of moderate duration repeated at regular intervals, but apparently not arranged in regular call series. Calls lack any frequency modulation, but exhibit moderate amplitude modulation, with call energy increasing from the beginning of the call and reaching its maximum at approximately half of the call’s duration (Fig. 38). Numerical parameters of 4 analysed calls are as follows: call duration (= note duration) 161–201 ms (180 ± 19 ms); inter-call intervals 2529–2716 ms (2638 ± 97 ms); dominant frequency 1256–1291 Hz (1274 ± 16 Hz); prevalent bandwidth 1100–3200 Hz; harmonic frequency bands recognizable at about 630, 1910, 2580 and 3160 Hz. Calls from the same recording have been described by Scherz et al. (2016a) using a slightly different terminological scheme. Slight differences in temporal measurements when compared to Scherz et al. (2016a) result from different recognition of the ‘tapering tail’ in calls, which we here consider to likely represent an echo effect.

The Malagasy adjective botabota meaning ‘chubby’, in reference to the body shape of this species. Used as an invariable noun in apposition.

Known from (1) Marojejy National Park (type locality), (2) Ambolokopatrika-Betaolana, and (3) Makira in northeastern Madagascar (Scherz et al. 2016a). Elevation: 860–1326 m a.s.l. Records from 750±200 m a.s.l. by Rakotoarimalala and Raselimanana (2023) cannot be verified as we have not examined material and have no DNA sequences, so they are not included here.

Rhombophryne botabota is a semi-fossorial or detriticolous species found in mid-elevation humid forest. In the vicinity of ‘Camp Simpona’ in November 2016, we found R. botabota to be moderately abundant during surveys. Specimens were routinely found by raking over quadrats of leaf litter, or collecting the quadrats in rice bags and sorting through them by hand. Previously, most specimens had been collected using pitfall traps (Scherz et al. 2016a). Some calls were heard, but no individuals could be observed calling. Paratype ZSM 538/2009 was recorded by Scherz et al. (2016a) to have a subulinid snail in its gut, making it the only record of gastropod consumption by a Rhombophryne species.

Lambert et al. (2017) mistakenly gave the holotype’s collection number as KU 340893 in their tables 1 and 2 and figure 3. The correct number is KU 340897.

The candidate species ‘Rhombophryne sp. 3’ of Vieites et al. (2009) and ‘Rhombophryne sp. Ca3’ of Perl et al. (2014) and Belluardo et al. (2022) from Tsaratànana is here included in R. nilevina due to its small uncorrected p distances (Tables S2, S3) and the results of our species delimitation analysis.

Carné and Vieites (2024) treated specimens from Marojejy and Anjanaharibe-Sud as ‘R. sp. cf. nilevina’ referring to them as ‘DCL “North”’, and treated R. sp. Ca03 as an unconfirmed candidate species ‘UCS “Sp. 3”’.

KU 340897 (CRH 798), an adult male, collected at mid-day on 8 February 2015 from ‘montane rainforest near the former village of Andemaka in Ranomafana National Park’ (ca 21.1287°S, 47.5054°E, 1240 m a.s.l.), Vatovavy-Fitovinany Region, South Central East Madagascar, by S.M. Lambert, E. Rajeriarison, and R.J. Fulgence (Figs 30, 31, 40).

One specimen: UADBA-A-CRH 799, an adult male, collected on the morning of 7 February 2015 from the same locality as the holotype, by S.M. Lambert and R.J. Fulgence (Fig. 39A–C).

ZSM 516/2016 (ZCMV 15215), an unsexed adult, collected on 18 November 2016 near ‘Camp Simpona’ (ca 14.4366°S, 49.7434°E, 1325 m a.s.l.), Marojejy National Park, Sava Region, northeastern Madagascar, by M.D. Scherz, A. Rakotoarison, M. Bletz, M. Vences, J. Razafindraibe, and A. Razafimanantsoa; MRSN A4598 (FN 7252), an adult male, collected on 12 December 1997 near ‘Camp 2’ Andranomadio (ca 14.7180°S, 49.5124°E, 820 m a.s.l.), Ambolokopatrika-Betaolana corridor, Sava Region, northeastern Madagascar, by F. Andreone.

According to our species delimitation, specimens formerly assigned to R. sp. Ca03 are also included in R. nilevina: MRSN A2631 (FAZC 11002), an adult female, ZSM 664/2001 (FGMV 2001.124), a subadult, ZSM 667/2001 (FGMV 2001.131), a <10 mm juvenile (the original genetic reference specimen for the candidate species), MRSN A3016 (FAZC 11135), an adult male (sexed by incision), and MRSN A3249 (FAZC 11086), a juvenile, all collected between 4 and 9 February 2001 at Antsahamanara (ca 14.05°S, 48.79°E, ca 1000 m a.s.l.), Tsaratànana Massif, Diana Region, Madagascar, by F. Andreone, F. Mattioli, J.E. Randrianirina, and M. Vences.

The holotype is to be used as the reference specimen for this species in 16S rRNA barcoding (16S3’ KY288475; Lambert et al. 2017), but by inclusion of R. sp. Ca03, so too is ZSM 667/2001 (16S3’ FJ559296; Vieites et al. 2009). ZSM 667/2001 (MV 2001.F5; KF611592) and MVTIS 2001.E50 (KF611593) (both originally R. sp. Ca03) are used as references for COI barcoding (Perl et al. 2014). The paratype and referred material conform well with the holotype in morphology, but see Variation section for comments on colour variation within the species. The paratype is topotypical. Assignment of specimens ZSM 516/2016, ZSM 667/2001, MRSN A2631, MRSN A4598, and MRSN A3016 (as well as tissue sample MV 2001-E50) is confirmed by molecular taxonomic identification (Fig. 2). KU 340897, MRSN A4598, MRSN A2631, and MVTIS 2001.E50 are present in the RAG1 haplotype network (Fig. 4).

Within the R. laevipes group, this species forms a subclade with R. botabota, R. sonaliaesp. nov. and R. anatialasp. nov. (described below) based on molecular phylogenetic data (Fig. 2; Belluardo et al. 2022). It is characterised by the possession of the following unique suite of characters: (1) large body size, adult SVL 41.2–57.2 mm; (2) head wider than long (HW/HL 1.42–1.81); (3) moderately small eyes (ED/HL 0.31–0.34); (4) relatively long hindlimbs (HIL/SVL 1.52–1.83); (5) small inner metatarsal tubercle (IMTL/FOL 0.10–0.14); (6) outer metatarsal tubercle absent; (7) second finger distinctly shorter than fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin smooth; (10) absence of chin barbels; (11) absence of pronounced superciliary spines; (12) presence or absence of white inguinal spots on a blackish background; (13) presence or absence of white spots on the posterior thigh and ventral shank; (14) unfortified skull without expansion of maxilla or posterior process of angulosplenial; (15) clavicles present, thin, curving; and (16) advertisement call (based on 7 analysed calls by one individual) pulsed, with (17) call duration 538–598 ms, (18) inter-call interval 42–126 s, and (19) dominant frequency 526–534 Hz.

Rhombophryne nilevina is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘G’ at site 389, ‘T’ at site 401, and ‘T’ at site 555; in 16S3’, ‘T’ at site 956, ‘T’ at site 1075, ‘A’ at site 1131, and ‘A’ at site 1157.

Within the genus Rhombophryne, R. nilevina can easily be distinguished from R. testudo, R. coudreaui, R. matavy, and R. maraoraosp. nov. by smooth skin (vs rough), absence of chin barbels (vs general presence), longer hindlimbs (HIL/SVL 1.52–1.83 vs 1.10–1.41); from R. mangabensis and R. savaka by much larger body size (SVL 41.2–57.2 mm vs 18.7–23.2 mm), longer relative forearm length (FARL/SVL 0.39–0.42 vs 0.33–0.38), well-ossified clavicles (vs poorly ossified), absence of black inguinal spots (vs presence in R. savaka); from R. mavokelysp. nov., R. ornata, and members of the R. ellae species group by the absence of reddish orange colouration on the posterior thigh and in the inguinal region (vs presence); from members of the R. minuta species group by usually shorter relative hindlimb length (HIL/SVL 1.52–1.81 vs 1.73–1.84), and less gracile habitus; from R. proportionalis by much larger adult body size (SVL 41.2–57.2 mm vs 11.0–12.3 mm); and from all members of the R. serratopalpebrosa species group by the absence of superciliary spines (vs presence).

Within the R. laevipes species group, see the accounts of R. laevipes and R. botabota above for distinction from those species. Note that several traits thought to distinguish R. nilevina from R. laevipes and R. botabota (e.g., absence of stark colour boundary between lateral head and dorsum, and absence of white spots in the inguinal region; Lambert et al. 2017) are now known to vary within the species (see Variation, below) and cannot be used as diagnostic traits anymore. For distinction from newly described members of this species group, see their respective descriptions below.

(a specimen of R. sp. Ca03 now included in R. nilevina): An adult female specimen in a good state of preservation. The right half of the body cavity is opened with the organs exposed; a piece of liver tissue was taken for genetic analysis. A small number of well-developed eggs lies in the dorsal part of the body cavity, which is taken up mostly with the thick-walled stomach.

Body robust. Head wider than long (HW/HL 1.71). Eyes quite small (ED/HL 0.32), pupils large, round. Snout rounded in dorsal and lateral view. Canthus rostralis distinct, concave. Loreal region concave, oblique. Nostril closer to tip of snout than to eye, slightly protuberant. Tympanum distinct, round, TDH/ED 0.75. Supratympanic fold distinct, slightly raised, running straight from posterior corner of eye over tympanum, curving gently ventrally posterior to the tympanum, demarcating the boundary of the dark brown lateral head colouration. Superciliary spines absent, but one white dot above each eye. Dorsal skin smooth in preservative, was slightly granular in life with a few larger granules (Fig. 41). Tongue broad, attached anteriorly, posteriorly free. Maxillary and vomerine teeth present, vomerine teeth present, curved, with small lateral diastemata, separated at the midline by a small gap. Choanae round, placed laterally in the roof of the mouth.

Forelimbs relatively short (FARL/SVL 0.443), strongly built. Fingers without webbing, moderately long, relative lengths 1 < 2 < 4 < 3, second finger distinctly shorter than fourth. Finger tips not expanded, rounded. Finger subarticular tubercles distinct, whitish, flat; inner metacarpal tubercle broad and flat, outer metacarpal/palmar tubercle indistinct, greyish. Hind limb strong, tibiotarsal articulation reaching between eye and nostril when adpressed anteriorly along the body. TIBL/SVL 0.537. Inner metatarsal tubercle present, oblong, whitish, somewhat bulging. Outer metatarsal tubercle absent. Toes not webbed; toes unreduced, toe lengths 1 < 2 < 5 < 3 < 4, fifth toe distinctly shorter than third; subarticular tubercles distinct, cream, slightly raised; toe tips not enlarged, rounded.

After 22 years in preservative, the colouration of the specimen remains quite vibrant, though less strongly contrasting than in life (Fig. 41). The base colour is a coffee brown across the dorsum, and venter except that it takes on a purplish tone over the abdomen, and a richer brown on the chin. On the dorsum, a broad pattern of darker brown is present, across which is strewn almost black markings, especially in an interocular line, a small trianguloid marking on the head, and a V-shaped area on the back. The lateral surface of the head is almost black, strongly separated from the dorsal body colouration. The inguinal region has a large blackish splotch and a series of small white spots. The dorsal surfaces of the hindlimbs have a series of dark brown crossbands; the posterior surfaces of the thighs are dark chocolate brown with a few light brown or cream spots. The cloaca marks the top of a blackish trapezoid, and above it there is a small blackish bar. The ventral thighs are coffee brown with small cream flecks, the ventral shanks are dark chocolate brown with cream spots. The dorsal foot is spotted with cream, its ventral surface dark brown. The ventral abdomen is cream and a purplish brown. Each finger and toe has a cream annulus before the distalmost phalange. The arm has blackish disjointed crossbands dorsally, but is coffee brown below, including on the palmar surface. Colouration in life was like in preservative but with a grey, rather than a brown, base colour (Fig. 41).

SVL ranges from 41.2–57.2 mm; for variation in other measurements, see Table S6. The newly examined material from northeastern Madagascar generally agrees well with the type series in morphology, despite extending the range of the species by well over 800 km. Unlike the types, northern specimens have distinct white spots in the inguinal region and on the posterior thigh and ventral shank. Many specimens have at least a spot, generally a bar, above the cloaca (absent from MRSN 4598), and all have a distinct colour border between their lateral head and dorsal head. MRSN A4598 has distinct vocal slits that confirm its sex as male.

The advertisement call recorded on 8 February 2015 (12:00 h) near Andemaka, Ranomafana National Park (air temperature estimated to be around 20 °C; presumably emitted by the holotype KU 340897), consists of a pulsed note of moderate to long duration, emitted at irregular and long intervals. Calls (= notes) exhibit distinct amplitude modulation, with call energy starting at low level, moderately increasing to about one fourth of the call’s duration, rapidly increasing after half of the call’s duration, reaching its maximum in its last quarter, followed by a decrease towards the call’s end. The second half of the call is characterized by a short intermittent drop in call energy. Pulses are very narrowly spaced in the second half of the call and very short in duration, with each pulse being apparently shorter than 2 ms, but almost impossible to measure exactly. In the first half of the call, pulses are longer in duration (ca. 9 ms) and repeated less rapidly. It is not possible to count the number of pulses per note (= call), but pulse repetition rate can roughly be calculated for each section of the note. Numerical parameters of 7 analysed calls are as follows: call duration (= note duration) 538–598 ms (561 ± 21 ms); inter-call intervals rather long and irregular, varying from 42–126 s (81 ± 41 s); pulse repetition rate within first half of the call 100 pulses/second, within second half of the call approximately 260–270 pulses/second; dominant frequency 526–534 Hz (530 ± 3 Hz); prevalent bandwidth 250–4500 Hz; numerous parallel frequency bands recognizable within the second half of the call, representing a reflection of pulse rate (see Köhler et al. 2017). Calls from the same recording have been described by Lambert et al. (2017) using a different terminological scheme.

The Malagasy adjective nilevina meaning ‘buried’, in reference to the habit of this species of calling from burrows that must be excavated to catch the frogs. Used as an invariable noun in apposition.

Records from northern Madagascar (Belluardo et al. 2022) dramatically increased the range of R. nilevina. Currently known from (1) Andemaka in Ranomafana National Park (type locality), (2) Ambolokopatrika, (3) Marojejy, and (4) Antsahamanara on the Tsaratànana Massif. Elevation: 1000–1325 m a.s.l.

Rhombophryne nilevina is a semi-fossorial or detriticolous species found in low- to mid-elevation humid forest. Lambert et al. (2017) reported that R. nilevina called during the day from burrows within the soil, and its calling activity was heightened by inclement weather. The newly referred specimens from the north were collected active above the ground in largely undisturbed primary rainforest.

The karyotype of a specimen assignable to this candidate species (FAZC 11063 from Tsaratànana) was described by Aprea et al. (2007) under the name ‘Plethodontohyla laevipes’. Its karyotype was 2n = 26, with a subtelocentric fourth chromosome pair. Nucleolar organiser regions were located in a peritelomeric position on the long arm of the second chromosome pair. Centromeric bands were CMA₃ and DAPI negative.

This species has been incorrectly assigned to Plethodontohyla alluaudi since at least 1975 (Blommers-Schlösser 1975, 1976; Blommers-Schlösser and Blanc 1991), but the identity of that nomen was recently clarified (Bellati et al. 2018), leaving this relatively well-known species in need of a new name.

The vast majority of mentions of ‘Mantipus alluaudi’, ‘Plethodontohyla alluaudi’, and ‘Rhombophryne alluaudi’ in publications between 1976 and 2018 in fact refer to this species, especially in all genetic analyses (Blommers-Schlösser 1976; Vences and Glaw 2003; Vences et al. 2003b, 2006; Vallan et al. 2004; Veith et al. 2004; Andreone et al. 2005; van der Meijden et al. 2005; Frost et al. 2006; Aprea et al. 2007; van der Meijden et al. 2007; Wollenberg et al. 2008; Vieites et al. 2009; D’Cruze et al. 2010; Glaw et al. 2010b; Raselimanana 2010; Perl et al. 2014; Scherz et al. 2014, 2015a, 2015b, 2016a, 2016b, 2017a, 2017b). The following exceptions are noted: records from the north of Madagascar, including Ambolokopatrika (Andreone et al. 2000), Manongarivo (Rakotomalala 2002), and Bemanevika (Rabearivony et al. 2010) probably refer to other species of Rhombophryne. Records from southeastern Madagascar likely refer to the true Plethodontohyla alluaudi (Ramanamanjato et al. 2002; Andrianarimisa et al. 2009; Ramanamanjato and Soanary 2011). Some records, e.g., that from Andringitra (Raxworthy and Nussbaum 1996) are uncertain, and are omitted from our treatment here, pending verification with voucher specimens.

Belluardo et al. (2022) mistakenly figured specimen MRSN A2610 of R. sp. Ca10 as specimen MRSN A2620 of R. sp. Ca19 in figure 1 of their paper.

This species was referred to as ‘Rhombophryne sp.’ by Bellati et al. (2018), ‘Rhombophryne sp. ex-alluaudi’ by Scherz (2020), ‘Rhombophryne sp. Ca19’ by Belluardo et al. (2022), and ‘Rhombophryne sp. 19’ and ‘CCS “Sp. 19”’ by Carné and Vieites (2024).

The new species is placed in a clade containing R. botabota, R. nilevina, and a further new species, R. anatialasp. nov. (described below), which was recovered as its sister species with high support (Belluardo et al. 2022). Genetic divergences among these lineages are less significant than those observed in the R. testudo group, but they all consistently differ among each other by >3.5% uncorrected p distance in the 16S3’ fragment (3.8% between R. sonaliaesp. nov. and R. anatialasp. nov.) and thus at a level typically indicative of species-level differentiation in Malagasy frogs (Vieites et al. 2009). Furthermore, the new species differs from R. botabota by larger body size, from R. nilevina by advertisement call differences, and from both these species by colour pattern (many individuals have a light brown dorsolateral stripe and large light spots in the inguinal region and posteroventrally on hindlimbs; see Diagnosis below). There is no detected haplotype sharing with any other Rhombophryne species in the nuclear gene RAG1 (Fig. 4). These differences are substantial and together with the molecular divergence strongly support the hypothesis of R. sonaliaesp. nov. constituting a new species. See also the Justification section for R. anatialasp. nov. below.

Carné and Vieites (2024) recovered two deep conspecific lineages of this species, from Iampirano (misspelled ‘Lampirano’) and Tsararano. Our species delimitation based on 16S3’ analyses also recovered these as conspecific.

ZSM 3/2002 (FGMV 2001.1271) an adult male, collected on 3 December 2001 in Andasibe (no precise coordinates), Alaotra-Mangoro Region, North Central East Madagascar, by M. Vences (Figs 30, 31, 44).

Seven specimens: ZSM 467/2005 (ZCMV 2221), a juvenile, and ZSM 466/2005 (ZCMV 2209), an ovigerous adult female, collected in February 2005 in pitfall traps in Andasibe (ca 18.9361°S, 48.4122°E, 939 m a.s.l.), Alaotra-Mangoro Region, North Central East Madagascar, by R. Dolch and Mitsinjo colleagues; MRSN A2620 (FN 6426), an adult male (sexed by incision), collected on 10 December 1996 in Tsararano (ca 14.907°S, 49.687°E, ca 700 m a.s.l.), Sava Region, northeastern Madagascar, by F. Andreone; MRSN A5034 (RJS 0883), an adult male, collected on 15 January 2005 in Iampirano (16.8218°S, 49.1843°E, ca 500 m a.s.l.), Analanjirofo Region, North Central East Madagascar, by J.E. Randrianirina; ZFMK 52765, an adult presumed male, collected on 16 February 1991 in Andasibe (ca 18.9245°S, 48.4149°E, ca 940 m a.s.l.), Alaotra-Mangoro Region, North Central East Madagascar, by F. Glaw and M. Vences (Fig. 43A–D); UADBA 20308 (ZCMV 968), an adult male, collected on 21 February 2004 in Torotorofotsy (ca 18.874°S, 48.373°E, ca 960 m a.s.l.), Alaotra-Mangoro Region, North Central East Madagascar, by M. Vences, E. Edwards, and C. Woodhead; MRSN A7143 (FAZC 15560), an adult male, collected on 6 March 2017 in Maromizaha (18.9653°S, 48.4652°E, ca 1000 m a.s.l.), Alaotra-Mangoro Region, North Central East Madagascar, by E. Coppola (Fig. 43H, I).

BMNH 1986.28, an unsexed adult, collected on 8 July 1985 by C.J. Raxworthy at ‘Camp 5’ in Zahamena Reserve (ca 17.67°S, ca 48.83°E, elevation unknown), Analanjirofo Region, North central east Madagascar, by C.J. Raxworthy. UADBA-A 62371 (MSZC 1480), collected on 13 March 2026 by Sandratra Rakotomanga, Alice Petzold, and Mark D. Scherz near Torotorofotsy (18.76965°S, 48.43532°E, 953 m a.s.l.), Alaotra-Mangoro Region, North Central East Madagascar; this specimen has been partly dissected in order to sequence and annotate its genome.

The paratype UADBA 20308 (ZCMV 968) is used as the reference specimen for this species in 16S rRNA barcoding (16S3’ and 16S5’ EU341105; Vieites et al. 2009) and COI barcoding (COIKF611584; Perl et al. 2014). The sequence of the holotype is identical to the sequence of this specimen in 16S3’ (AY594112), and it differs by two mutations in 16S5’ (99.7% identical; AY594074), and by five mutations in COI (99.1% identical; EF396063). All paratypes and referred specimens conform well with the holotype in morphology. Assignment of specimens ZSM 466/2005, MRSN A2620, MRSN A5034, and MRSN A7143 is further confirmed by molecular taxonomic identification (Fig. 2). ZSM 3/2002, MRSN A2620, and MRSN A7143 are present in the RAG1 haplotype network (Fig. 4).

Within the R. laevipes group, this species is sister to R. anatialasp. nov. (described below) based on molecular phylogenetic data (Fig. 2; Belluardo et al. 2022). It is characterised by the possession of the following unique suite of characters: (1) medium to large body size, adult SVL 33.0–44.7 mm; (2) head wider than long (HW/HL 1.59–1.71); (3) moderately small eyes (ED/HL 0.28–0.36); (4) relatively long hindlimbs (HIL/SVL 1.44–1.53); (5) small inner metatarsal tubercle (IMTL/FOL 0.12–0.15); (6) outer metatarsal tubercle absent; (7) second finger distinctly shorter than fourth; (8) third toe distinctly longer than fifth, reaching or barely surpassing the joint of the first and second phalange of the fourth toe; (9) dorsal skin smooth; (10) absence of chin barbels; (11) absence of pronounced superciliary spines; (12) presence of large white or yellowish inguinal spots on a black background, and a light-brown dorsolateral stripe broadening from the eye towards the inguinal region; (13) presence of large white or yellowish spots on a black background on the posterior thigh and ventral surfaces of the shanks; (14) unfortified skull without expansion of maxilla or posterior process of angulosplenial; (15) clavicles present, thin, curving; and (16) advertisement call (based on 4 analysed calls by one individual) pulsed, with (17) call duration 207–228 ms, (18) inter-call interval long (not measured), and (19) dominant frequency 785–828 Hz.

Rhombophryne sonaliaesp. nov. is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘T’ at site 392, ‘T’ at site 445, and ‘A’ at site 740; in 16S3’, ‘A’ at site 1027, ‘T’ at site 1076, ‘C’ at site 1104, and ‘T’ at site 1172.

Within the genus Rhombophryne, R. sonaliaesp. nov. can usually be distinguished from all species except R. anatialasp. nov. described below by the presence of a light brown dorsolateral stripe expanding from the eyes towards the inguinal region. However, as this trait is not always present (Fig. 43E, F), additional traits are necessary for a reliable diagnosis.

Rhombophryne sonaliaesp. nov. can easily be distinguished from R. testudo, R. coudreaui, R. matavy, and R. maraoraosp. nov. by smooth skin (vs rough), absence of chin barbels (vs general presence), longer hindlimbs (HIL/SVL 1.44–1.53 vs 1.10–1.41); from R. mangabensis and R. savaka by larger body size (SVL 33.0–44.7 mm vs 18.7–23.2 mm), presence of multiple large light-coloured inguinal spots (vs black inguinal ocelli in R. savaka), and pulsed (vs tonal) advertisement call; from R. mavokelysp. nov., R. ornata, and members of the R. ellae species group by the absence of reddish orange colouration on the posterior thigh and in the inguinal region (vs presence); from members of the R. minuta species group by shorter hindlimb length (HIL/SVL 1.44–1.53 vs 1.73–1.84), and less gracile habitus; from R. proportionalis by much larger adult body size (SVL 33.0–44.7 mm vs 11.0–12.3 mm); and from all members of the R. serratopalpebrosa species group by the absence of superciliary spines (vs presence).

Within the R. laevipes species group, R. sonaliaesp. nov. can be distinguished from R. laevipes by shorter hindlimbs (HIL/SVL 1.44–1.53 vs 1.62–1.86), larger inner metatarsal tubercle (IMTL/FOL 0.12–0.15 vs 0.08–0.11), and advertisement call with a higher dominant frequency (785–828 Hz vs 612–631 Hz); from R. botabota by larger body size (SVL 33.0–44.7 mm vs 24.2–32.2 mm), presence of large light-coloured spots in the inguinal region and on the posterior thigh and ventral shank (vs absence), and pulsed (vs tonal) advertisement call that is slightly longer (call duration 207–228 ms vs 161–201 ms) and lower in dominant frequency (785–828 Hz vs 1256–1291 Hz); and from R. nilevina by generally shorter hindlimbs (HIL/SVL 1.44–1.83 vs 1.52–1.69), and advertisement call that is shorter (call duration 207–228 ms vs 538–598 ms) and higher in dominant frequency (785–828 Hz vs 526–534 Hz). For distinction from other newly described members of this species group, see their respective descriptions below.

An adult male specimen in a moderately good state of preservation (Fig. 30). The abdomen is opened with the organs exposed. Tip of right third finger missing.

Body robust and rotund. Head broader than trunk, wider than long (HW/HL 1.59). Eyes quite small (ED/HL 0.28), pupils small, round. Snout rounded in dorsal and slightly truncate in lateral view. Canthus rostralis distinct, concave. Loreal region concave, oblique. Nostril closer to tip of snout than to eye, slightly protuberant. Tympanum indistinct, round, TDH/ED 0.64. Supratympanic fold distinct, slightly raised, running straight from posterior corner of eye over tympanum, curving gently ventrally posterior to the tympanum. Slight colour border between lateral head and dorsal head, with the lateral head being lighter in colour. Superciliary spines absent, no white dots above the eyes. Dorsal skin smooth in preservative. Tongue broad, attached anteriorly, posteriorly free. Maxillary and vomerine teeth present, vomerine teeth curved, with a dent each row marginally closer to midline than to lateral end, separated at the midline by a small gap. Choanae round and surrounded by pigment, placed laterally in the roof of the mouth.

Forelimbs relatively short (FARL/SVL 0.386), strongly built. Fingers without webbing, moderately long, relative lengths 1 < 2 < 4 < 3, second finger distinctly shorter than fourth (Fig. 31). Finger tips not expanded, rounded. Finger subarticular tubercles distinct, whitish, flat; inner metacarpal tubercle broad and rounded, outer metacarpal/palmar tubercle indistinct, greyish. Hind limb strong, tibiotarsal articulation reaching between tympanum and eye when adpressed anteriorly along the body. TIBL/SVL 0.407. Inner metatarsal tubercle present, oblong, whitish, distinctly raised. Outer metatarsal tubercle absent. Toes not webbed; toes unreduced, toe lengths 1 < 2 < 5 < 3 < 4, fifth toe distinctly shorter than third, third toe just exceeding the base of the second phalange of the fourth toe; subarticular tubercles indistinct; toe tips slightly enlarged, rounded (Fig. 31).

After 20 years in preservative, the base colour is a coffee brown across the dorsum, and a lighter brown on the limbs. The central dorsum is immaculate, bordered either side by greyish wavy patterns riddled with tiny white points, giving an overall ‘milky way’ impression. There is a slight colour border between the dorsal colour and the lateral head, with the lateral head lighter in colour than the dorsal surface. The inguinal region bears several large white spots which also extend onto the anterior thigh. There are also several white spots on the posterior thigh, ventral shank, and dorsal foot. The ventral thigh is light brown flecked with cream. The ventral feet are a light chocolate brown. A light annulus is present before the terminal phalange of each finger and toe. The legs lack crossbands dorsally. The arms have a single crossband on the lower arm. The palmar surface is grey-brown. The chin is light brown, the ventral abdomen flecked with cream. The cloaca region is unmarked, and there is no blackish bar above it. The colouration in life was not recorded.

Type series SVL 33.0–44.7 mm (n = 5 adults). For variation in other measurements, see Table S6. Morphology is highly consistent. Third toe consistently reaching the second phalangeal articulation of the fourth toe or barely exceeding it. The most distinctive and constant feature is the diffuse light brown to grey stripe running from the eye toward the inguinal region flecked with tiny white specks, and distinct whitish or yellowish spots on the anterior and posterior thigh, inguinal region, and ventral shank. Only in MRSN A2620 are these spots not clearly defined and rather small. In all other specimens they are extremely strongly defined. Ventral colour likewise consistent, but varying over the posterior abdomen from covered in flecks (ZSM 467/2005) to almost immaculate (MRSN A5034). Chin dark in all available specimens. The referred specimen, BMNH 1986.28, is somewhat smaller than the rest of the type series, and its dorsal colouration is more mottled.

The advertisement call recorded on 21 February 2004 (15:20 h) at Torotorofotsy (air temperature 19.1 °C) consists of a single pulsed note of moderate duration repeated at long irregular intervals (Fig. 45). Calls (= notes) exhibit distinct amplitude modulation, with call energy starting at low level, constantly increasing to about two thirds of the call’s duration where energy reaches its maximum, followed by a decrease towards the call’s end. Pulses are more narrowly spaced in the last two thirds of the call’s duration and very short in duration, with each pulse having around 1 ms duration, but impossible to measure exactly. In the first third of the call, pulses are longer in duration (5–7 ms) and repeated less rapidly. It is not possible to count the number of pulses per note (= call), but pulse repetition rate can roughly be calculated for each section of the note. Numerical parameters of 4 analysed calls from 2 individuals are as follows: call duration (= note duration) 207–228 ms (219 ± 10 ms); inter-call intervals apparently long and irregular and not measured (probably poorly motivated calling; see Köhler et al. 2017); pulse repetition rate within first half of the call approximately 130–190 pulses/second, within second half of the call approximately 370–420 pulses/second; dominant frequency 785–828 Hz (805 ± 23 Hz); prevalent bandwidth 350–4000 Hz; numerous parallel frequency bands recognizable within the last two thirds of the call, representing a reflection of pulse rate (see Köhler et al. 2017). The call recording analysed herein has been published on the audio CD by Vences et al. (2006) as ‘Plethodontohyla alluaudi’ (CD 3, track 28). Assignment to this species is tentative, as the calling individual was not vouchered.

We dedicate this species to Sonali Garg, in recognition of her substantial contributions to knowledge of taxonomy and biogeography of South and Southeast Asian frogs, especially microhylids (e.g., Garg et al. 2018, 2019, 2022; Garg and Biju 2019).

Evidently widespread in eastern to northeastern Madagascar, but seldom encountered. Definitive records come from (1) Andasibe (type locality), (2) Torotorofotsy, (3) Iampirano, (4) Tsararano, (5) Maromizaha (Ratsimbazafy et al. 2008), and (6) Mandraka (Blommers-Schlösser 1975). We have examined a referrable specimen from (7) Zahamena (BMNH 1986.28). It has also been recorded in the (8) Ambatovy-Analamay region (Raselimanana 2010), and (9) An’Ala (Vallan et al. 2004). Elevation: ca 500–1200 m a.s.l.

Rhombophryne sonaliaesp. nov. is a semi-fossorial or detriticolous species found in mid-elevation humid forest. Calling activity occurs mostly during or shortly after rain, often during the day but probably also at night. The captured calling male from Torotorofotsy was calling during the day from a burrow in the forest floor under the leaf litter. The gut contents of MRSN A2620 included four large termites (each ca 9 mm long), the remains of a katydid (shanks 10.8 mm), a whole spider, a staphylinid rove beetle (ca 9 mm), and three small ants, as well as two parasitic worms. There was only little detritus other than these arthropods in the gut. Those of MRSN A5034 contained a beetle tentatively assigned to Elateridae (click beetles), measuring 10.6 mm, a beetle elytrum, pieces of an ant, and a few large pieces of leaf, as well as two small parasitic worms. Field notes on ZFMK 52765 indicate that it had a caterpillar, among other things, in its stomach. Vallan et al. (2004) recorded a slight increase in detection of this species after logging of forest in An’Ala, but this may have been coincidental. Blommers-Schlösser (1975) found a female under a fallen tree trunk at 1200 m a.s.l. Referred specimen UADBA-A 62371 (MSZC 1480) was collected calling (including in response to playbacks) after rain at 10h13 in the morning on 13 March 2026. It was calling from under ca 10 cm of soil at the base of a tree; whilst excavating it, we encountered an adult Plethodontohyla notosticta, an adult Paradoxophyla cf. palmata, and a putative adult Madascincus cf. nanus.

The karyotype was originally described by Blommers-Schlösser (1976) based on a female from Mandraka (as ‘Mantipus alluaudi’). It consists of 10 large and 16 small pairs of chromosomes (2n = 26). Pair 4 subtelocentric, pairs 3, 7, 10, and 13 submetacentric. Aprea et al. (2007) provided a new description based on the holotype (ZSM 3/2002, as ‘Plethodontohyla alluaudi’). They reported both the fourth and the eleventh chromosome pairs to be subtelocentric. Nucleolar organiser regions were located in a peritelomeric position on the long arm of the second chromosome pair. Centromeric bands were DAPI positive.

MRSN A5477, a specimen housed in the same jar as MRSN A5524, the specimen of R. maraoraosp. nov. discussed above, likewise allegedly comes from Tsingy de Bemaraha in western Madagascar, but agrees morphologically with R. anatiala. We are confident that this specimen, too, was collected in northeastern Madagascar. However, as for R. maraorao, we do not include the mislocated specimen in the diagnosis of the species (also because we lack DNA sequence data on it), in order to avoid introducing errors, but recognise that it is probably referrable to R. anatialasp. nov. nonetheless.

This species was listed as ‘Rhombophryne sp. 1’ by Vieites et al. (2009) and ‘Rhombophryne sp. Ca01’ by Scherz et al. (2016b) and Belluardo et al. (2022), and ‘Rhombophryne sp. 1’ and ‘UCS “Sp. 1”’ by Carné and Vieites (2024).

The new species was found to be the sister species of R. sonaliaesp. nov. (described above) with high support based on a multigene phylogeny (Belluardo et al. 2022). The genetic divergences between these two lineages is >3.8% uncorrected p distance in the 16S3’ fragment, and thus at a level typically indicative of species-level differentiation in Malagasy frogs (Vieites et al. 2009). We found absence of haplotype sharing between R. anatialasp. nov. and R. sonaliaesp. nov. and between R. anatialasp. nov. and any other Rhombophryne species in the analysed fragment of the nuclear gene RAG1 (Fig. 4). Morphologically, the two lineages differ in relative toe length (see Diagnosis below). Taken together, and based on other example of pairs of species of Malagasy frogs allopatrically distributed in the North East vs. Northern Central East of Madagascar, we consider the hypothesis of these two lineages representing two distinct species as most likely, although we acknowledge the need for in-depth study of their contact zone. In the highly unlikely case future studies will find the two nomina to be subjective synonyms, we recommend as first reviser action to give priority to sonaliae over anatiala.

MRSN A2696 (RJS 0597) an adult female, collected on 15 February 2002 at ‘Camp 7’ Antsiranana Faritany (15.4177°S, 49.9403°E, ca. 800 m a.s.l.), Amparihy, Masoala Peninsula, Analanjirofo Region, northeastern Madagascar, by J.E. Randrianirina (Figs 30, 31, 47).

Two specimens: MRSN A4544 (FAZC 10314; Fig. 46), and MRSN A4600 (FAZC 10304), two ovigerous adult females, collected on 11 and 12 December 1999 (respectively) at ‘Camp 5’ Menamalona (15.3812°S, 49.9878°E, ca 800 m a.s.l.), Ilampy Corridor, Masoala Peninsula, Analanjirofo Region, northeastern Madagascar, by F. Andreone and J.E. Randrianirina.

The paratype MRSN A4544 is used as the reference specimen for this species in 16S rRNA barcoding (16S3’ FJ559295; Vieites et al. 2009). COI is so far not available for this species. The 16S3’ sequence of the holotype is identical to that of this specimen (OL780571) and has also been sequenced for 16S5’ (OL780600). Both paratypes conform well with the holotype in morphology (MRSN A4544 could only be examined from photographs; Fig. 46). The assignment of MRSN A4600 is further confirmed by molecular taxonomic identification (Fig. 2). MRSN A2696 and MRSN A4544 are present in the RAG1 haplotype network (Fig. 4).

A further specimen, MRSN A2584 (RJS 0348), is recovered by molecular taxonomic identification as conspecific, but could not be examined morphologically. Database records indicate that this should be a Spinomantis specimen, indicating some kind of specimen or metadata mix-up. To avoid confusion, we have not designated this specimen as a paratype.

Within the R. laevipes group, this species is sister to R. sonaliaesp. nov. (described above) based on molecular phylogenetic data (Fig. 2; Belluardo et al. 2022). It is characterised by the possession of the following unique suite of characters: (1) medium to large body size, adult SVL 34.3–37.9 mm; (2) head wider than long (HW/HL 1.56–1.76); (3) moderately small eyes (ED/HL 0.31–0.35); (4) relatively long hindlimbs (HIL/SVL 1.51–1.58); (5) small inner metatarsal tubercle (IMTL/FOL 0.11–0.13); (6) outer metatarsal tubercle absent; (7) second finger subequal to fourth; (8) third toe distinctly longer than fifth, reaching the second phalange of the fourth toe; (9) dorsal skin smooth; (10) absence of chin barbels; (11) absence of pronounced superciliary spines; (12) presence of large white inguinal spots on a black background, and a light-brown dorsolateral stripe broadening from the eye towards the inguinal region; (13) presence of large white or yellowish spots on a black background on the posterior thigh and ventral surfaces of the shanks; (14) unfortified skull without expansion of maxilla or posterior process of angulosplenial; and (15) clavicles present, thin, curving.

Rhombophryne anatialasp. nov. is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘G’ at site 259, ‘C’ at site 654, and ‘G’ at site 739. No diagnostic sites were identified for 16S3’.

Within the genus Rhombophryne, R. anatialasp. nov. can usually be distinguished from all species except R. sonaliaesp. nov. described above by the presence of a light brown dorsolateral stripe expanding from the eyes towards the inguinal region. However, as this trait is not always present (Fig. 46A), additional traits are necessary for a reliable diagnosis.

Rhombophryne anatialasp. nov. can easily be distinguished from R. testudo, R. coudreaui, R. matavy, and R. maraoraosp. nov. by smooth skin (vs rough), absence of chin barbels (vs general presence), longer hindlimbs (HIL/SVL 1.51–1.58 vs 1.10–1.41); from R. mangabensis and R. savaka by larger body size (SVL 34.3–37.9 mm vs 18.7–23.2 mm), and presence of multiple large light-coloured inguinal spots (vs black inguinal ocelli in R. savaka); from R. mavokelysp. nov., R. ornata, and members of the R. ellae species group by the absence of reddish orange colouration on the posterior thigh and in the inguinal region (vs presence); from members of the R. minuta species group by shorter hindlimb length (HIL/SVL 1.51–1.58 vs 1.73–1.84), and less gracile habitus; from R. proportionalis by much larger adult body size (SVL 34.3–37.9 mm vs 11.0–12.3 mm); and from all members of the R. serratopalpebrosa species group by the absence of superciliary spines (vs presence).

Within the R. laevipes species group, R. anatialasp. nov. can be distinguished from R. laevipes by shorter hindlimbs (HIL/SVL 1.51–1.58 vs 1.62–1.86), and larger inner metatarsal tubercle (IMTL/FOL 0.11–0.13 vs 0.08–0.11); from R. botabota by larger body size (SVL 34.3–37.9 mm vs 24.2–32.2 mm), and presence of large light-coloured spots in the inguinal region and on the posterior thigh and ventral shank (vs absence); and from R. nilevina by smaller body size (SVL 34.3–37.9 mm vs 41.2–57.2 mm). As far as is known, Rhombophryne anatialasp. nov. can only be distinguished morphologically from R. sonaliaesp. nov. by the longer third toe, reaching the midpoint of the second phalange of the fourth toe (vs reaching or barely surpassing the joint of the first and second phalange of the fourth toe). For distinction from the last newly described member of this species group, see its description below.

Specimen in a moderately good state of preservation, though slightly soft (Fig. 30). An incision made along the left flank to assess the sex, and part of the tongue taken as a tissue sample. Small ova, ovaries, and fallopian tubes clearly visible.

Body robust and rotund. Head wider than long (HW/HL 1.76). Eyes quite small (ED/HL 0.31), slightly depressed, pupils small, oval. Snout rounded in dorsal and slightly truncate in lateral view. Canthus rostralis distinct, concave. Loreal region concave, oblique. Nostril equidistant between tip of snout and eye, slightly protuberant. Tympanum indistinct, round, TDH/ED 0.59. Supratympanic fold distinct, slightly raised, dark brown, running straight from posterior corner of eye over tympanum, curving gently ventrally posterior to the tympanum to above the forearm’s insertion. Lateral head similar in colour to dorsal head, except for the supratympanic fold. Superciliary spines absent, one subtle light dot above each eye. Dorsal skin smooth in preservative. Tongue partly taken as tissue sample, originally broad, attached anteriorly, posteriorly free. Maxillary and vomerine teeth present, vomerine teeth curved, without pronounced height variation, separated at the midline by a small gap. Choanae round and surrounded by pigment, placed laterally in the roof of the mouth.

Forelimbs relatively short (FARL/SVL 0.380), strongly built. Fingers without webbing, moderately long, relative lengths 1 < 2 < 4 < 3 on left hand, 1 < 4 < 2 <3 on right, in both cases distinctly so (Fig. 31). Finger tips not expanded, rounded. Finger subarticular tubercles distinct, whitish, flat; inner metacarpal tubercle broad and rounded, outer metacarpal/palmar tubercle indistinct, greyish. Hind limb strong, tibiotarsal articulation reaching between tympanum and eye when adpressed anteriorly along the body. TIBL/SVL 0.428. Inner metatarsal tubercle present, oblong, whitish, distinctly raised. Outer metatarsal tubercle absent. Toes not webbed; toes unreduced, toe lengths 1 < 2 < 5 < 3 < 4, fifth toe distinctly shorter than third, third toe extending to the middle of the second phalange of the fourth toe; subarticular tubercles slightly distinct; toe tips slightly enlarged, rounded (Fig. 31).

After 19 years in preservative, the base colour is a coffee brown across the dorsum, and a darker brown on the limbs. The dorsum is mottled brown, with a clear V-shaped marking over the suprascapular region. Behind the eyes, running towards the inguinal region, are lighter brown wavy patterns riddled with tiny white points, very similar to R. sonaliaesp. nov. No distinct colour difference between the lateral and dorsal head except on the supratympanic fold, which is dark brown. The inguinal region bears several large white spots which also extend onto the anterior thigh, on a dark brown background. There are also several white spots on the posterior thigh, ventral shank, and dorsal foot. The ventral thigh is mostly cream, mottled with light brown. The ventral feet are a light brown. A light annulus is present before the terminal phalange of each finger and toe. The legs have distinct crossbands on the thigh, shank, tarsus, and foot. The arms have a single crossband on the lower arm. The palmar surface is grey-brown. The chin is light brown, the ventral abdomen mostly cream, with a few brown flecks. The cloaca region is unmarked, and there is no blackish bar above it.

SVL 34.3–37.9 mm (n = 2). For variation in other measurements see Table S6. MRSN A4600 has a distinctly different skin texture in preservative, and is also much less mottled than the holotype. It lacks the V-shaped marking of the dorsum and the crossbands on the legs of the holotype. MRNS A4544 likewise lacks the V-shaped marking on the dorsum, but does have the crossbands on its legs.

The call of this species is unknown.

The Malagasy adjective anatiala meaning ‘in the forest’, in reference to the habitat of this species in the rainforests of Masoala. Used as an invariable noun in apposition.

This species is only known from (1) Amparihy (type locality) and (2) Menamalona on the Masoala Peninsula. Elevation: 778–800 m a.s.l.

Little is known of the ecology of this species, but we presume that it is similar to its sister species, R. sonaliaesp. nov., in its ecology and behaviour; see the account of that species, above.

This species was listed as ‘Rhombophryne sp. 10’ by Vieites et al. (2009) and ‘Rhombophryne sp. Ca10’ by Scherz et al. (2015b), Lambert et al. (2017), Scherz (2020), and Belluardo et al. (2022), and ‘Rhombophryne sp. 10’ and ‘UCS “Sp. 10”’ and ‘UCS “Sp. 20”’ by Carné and Vieites (2024). A specimen of this species (MRSN A2610) was mistakenly figured as the specimen MRSN A2620 of ‘R. sp. Ca19’ by Belluardo et al. (2022).

The new species was found to be the sister species of R. sp. Ca15 from Betampona of which no further data are available (see account on this candidate species below). Together, the clade of these two lineages is sister to all other species of the R. laevipes group based on a multigene phylogeny (Belluardo et al. 2022) which by itself already excludes conspecificity with any of the other nominal species. Genetic divergence of R. kotrobaratrasp. nov. to all other nominal species of Rhombophryne is >7.5% uncorrected p distance in the 3’-terminal fragment of 16S and thus much higher than the 3% level typically indicative of species-level differentiation in Malagasy frogs (Vieites et al. 2009). There is no haplotype sharing in the analysed fragment of the nuclear gene RAG1 between R. kotrobaratrasp. nov. and any other species of the Rhombophryne genus in the analysed dataset (Fig. 4). Furthermore, it also differs from other nominal species in the R. laevipes group by morphological characters (see Diagnosis below), and its status as distinct species is therefore beyond doubt. More research is necessary to understand the status of R. sp. Ca15 (see below).

MRSN A2990 (RJS 0581), an adult female, collected on 17 February 2002 at ‘Camp 7’ Antsiranana Faritany (15.4177°S, 49.9403°E, ca. 778 m a.s.l.), Amparihy, Masoala Peninsula, Analanjirofo Region, northeastern Madagascar, by J.E. Randrianirina (Figs 30, 31).

Nine specimens: MRSN A2610 (FAZC 10312; Fig. 48A–C), an adult male, and MRSN A2599 (FAZC 10307), an adult female, collected on 11 and 13 December 1999 (respectively) at ‘Camp 5’ Menamalona (15.3812°S, 49.9878°E, ca 800 m a.s.l.), Ilampy Corridor, Masoala Peninsula, Analanjirofo Region, northeastern Madagascar, by F. Andreone and J.E. Randrianirina; MRSN A1845 (FN 6310), an adult female, collected on 3 December 1996 in Antsarahan’ny Tsararano (ca 14.9067°S, 49.6867°E, ca 700 m a.s.l.), Sava Region, northeastern Madagascar, by F. Andreone (Fig. 48E, F); MRSN A2609 (FN 7519; Fig. 49), an adult male, and MRSN A2601 (FN 7560), an adult female, collected on 23 and 24 November 1998 (respectively) at ‘Camp 2’ Beanjada (15.2638°S, 49.9583°E, ca 1000 m a.s.l.), Masoala Peninsula, Analanjirofo Region, northeastern Madagascar, by F. Andreone and J.E. Randrianirina; UADBA-A-APR 12594, UADBA-A-APR 12541, and UADBA-A-APR 12563, a putative male and two small juveniles (respectively), collected on 16–19 May 2016 at mid-elevation in Marojejy National Park (14.4559°S, 49.7749°E, 765–780 m a.s.l.), Sava Region, northeastern Madagascar, by A.P. Raselimanana; UADBA-A-APR 12765, an adult female, collected on 1 June 2016 at mid-elevation in southwestern Marojejy National Park (14.5074°S, 49.6153°E, 835 m a.s.l.), Sava Region, northeastern Madagascar, by A.P. Raselimanana.

The paratype MRSN A2610 (FAZC 10312) is used as the reference specimen for this species in 16S rRNA barcoding (16S5’ AY594073; Andreone et al. 2005; 16S3’ AY594111; Vieites et al. 2009). The holotype is used as the reference specimen for COI barcoding (COIOL790134; Belluardo et al. 2022). The 16S sequence of the holotype differs from the 16S reference sequence by eight mutations and three gaps in the 16S3’ fragment (98% identical; OL780580). All paratypes and referred specimens conform well with the holotype in morphology; no further specimens are sequenced. MRSN A2990 and MRSN A2610 are present in the RAG1 haplotype network (Fig. 4).

Within the R. laevipes group, this species along with R. sp. Ca15 represents the sister clade of all other group members based on molecular phylogenetic data (Fig. 2; Belluardo et al. 2022). It is characterised by the possession of the following unique suite of characters: (1) medium body size, adult SVL 24.1–33.0 mm; (2) head wider than long (HW/HL 1.46–1.64); (3) moderately small eyes (ED/HL 0.34–0.44); (4) long hindlimbs (HIL/SVL 1.81–1.92); (5) small inner metatarsal tubercle (IMTL/FOL 0.09–0.11); (6) outer metatarsal tubercle sometimes present; (7) second finger distinctly shorter than fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin granular with scattered warts in life; (10) absence of chin barbels; (11) absence of pronounced superciliary spines; (12) absence of distinct inguinal spots; (13) presence of bright orange colouration on the hidden surfaces of the legs in life; (14) unfortified skull without expansion of maxilla or posterior process of angulosplenial; and (15) clavicles present, thin, curving.

Rhombophryne kotrobaratrasp. nov. is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16S rRNA gene (positions relative to the full 16S sequence of Anilany helenaeMZ751042): in 16S5’, ‘C’ at site 288, ‘T’ at site 355, and ‘T’ at site 402. No diagnostic sites were identified for 16S3’.

Within the genus Rhombophryne, R. kotrobaratrasp. nov. is highly distinctive, and can be distinguished from all other species by the combination of orange colouration on the hidden surfaces of the legs (otherwise present only in the R. ellae species group and R. mavokelysp. nov.), absence of inguinal ocelli (present in R. ellae and R. quentinisp. nov.), and long legs (HIL/SVL 1.81–1.92 vs 1.50–1.61 in R. mavokelysp. nov., 1.40–1.80 in the R. ellae species group). It also typically has a distinctive dark chevron dorsally, which can be useful to distinguish it from most other species. These chevrons and in general the presence of a rather tubercular dorsal skin appear to distinguish the species from all other nominal species in the R. laevipes group.