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 (COI KF611596/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 helenae MZ751042): 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. maraorao sp. 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 testudo ZSM 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. maraorao sp. 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. maraorao sp. 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 helenae MZ751042): 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. maraorao sp. 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. maraorao sp. 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. maraorao sp. 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. maraorao sp. nov., below. Based on the locality of this specimen and its apparent affinity with R. maraorao sp. 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 ‘Rhombophryne sp. 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 (COI KF611589; 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 helenae MZ751042): 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. maraorao sp. 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. maraorao sp. 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 (COI KF611588/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 helenae MZ751042): 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 quentini sp. 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 (COI KF611594; 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 helenae MZ751042): 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. mavokely sp. 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. maraorao sp. 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. maraorao sp. 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. maraorao sp. 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. maraorao sp. nov., as these two species are only now being recognised as distinct, with R. maraorao sp. nov. apparently occurring north of R. coudreaui. However, these records may also refer to R. mavokely sp. 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 maraorao sp. 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 helenae MZ751042): 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. maraorao sp. 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 maraorao sp. 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. maraorao sp. 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. maraorao sp. 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. maraorao sp. 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 maraorao sp. 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 mavokely sp. 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 helenae MZ751042): 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. mavokely sp. nov. can easily be distinguished from all species except R. ellae, R. ornata, and two other species described below (R. quentini sp. nov. and R. kotrobaratra sp. 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. quentini sp. nov. and R. kotrobaratra sp. 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 mavokely sp. nov. occurs syntopically or in near sympatry with the closely related R. savaka. Aside from colouration, R. mavokely sp. 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 mavokely sp. 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 helenae MZ751042): 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. maraorao sp. 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. mavokely sp. 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. maraorao sp. 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. maraorao sp. nov., and not expanded in R. mavokely sp. 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. mavokely sp. 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. maraorao sp. nov., R. mavokely sp. 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. mavokely sp. 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. maraorao sp. 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. mavokely sp. 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. mavokely sp. 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. mavokely sp. nov.), around half (R. savaka, R. maraorao sp. 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. maraorao sp. 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. maraorao sp. 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. maraorao sp. nov., but the posterior quarter is free in all other species.

Iliac shafts with strong dorsal crests in all species except R. mavokely sp. 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. mavokely sp. 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. maraorao sp. nov. and R. mavokely sp. 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 (COI KF611587; 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 helenae MZ751042): 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. maraorao sp. 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. mavokely sp. 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 (COI KF611585; 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. sonaliae sp. nov. and R. anatiala sp. 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 helenae MZ751042): 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. maraorao sp. 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. mavokely sp. 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.