104 urn:lsid:arphahub.com:pub:f2cd1fff-21e4-581f-a7fa-850997197b7f urn:lsid:zoobank.org:pub:B1C81912-2D17-4CD8-8D2C-EFEAAAB2EF75 Vertebrate Zoology VZ 1864-5755 2625-8498 Senckenberg Gesellschaft für Naturforschung 10.3897/vz.73.e101065 101065 Research Article Ctenomyidae Mammalia Placentalia Rodentia Theria Taxonomy An appraisal of the species richness of the Ctenomys mendocinus species group (Rodentia: Ctenomyidae), with the description of two new species from the Andean slopes of west-central Argentina Teta Pablo https://orcid.org/0000-0001-8694-0498 1 Jayat J. Pablo 2 Alvarado-Larios Raquel https://orcid.org/0000-0001-8322-287X 3 Ojeda Agustina A. https://orcid.org/0000-0003-2007-5061 3 Cuello Pablo 3 D’Elía Guillermo guille.delia@gmail.com https://orcid.org/0000-0001-7173-2709 4 División Mastozoología, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Avenida Ángel Gallardo 470, C1405DJR Buenos Aires, Argentina Unidad Ejecutora Lillo (UEL), CONICET-Fundación M. Lillo, Miguel Lillo 251, CP 4000, San Miguel de Tucumán, Tucumán, Argentina Laboratorio de Filogeografía, Taxonomía Integrativa y Ecología, Instituto Argentino de Investigaciones de las Zonas Áridas (IADIZA), CCT-CONICET Mendoza, Avenida Ruiz Leal s/n, CP 5500, Mendoza, Argentina Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, Chile Colección de Mamíferos, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, Chile

Corresponding author: Guillermo D’Elía (guille.delia@gmail.com)

Academic editor Clara Stefen

 2023 16 05 2023 73 451 474 1386E629-B670-5A10-AD7E-9D43F1063167 BD96329D-A6E3-46C8-94A9-50C1B198BB89 7947654 27 01 2023 18 04 2023 Pablo Teta, J. Pablo Jayat, Raquel Alvarado-Larios, Agustina A. Ojeda, Pablo Cuello, Guillermo D’Elía This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. http://zoobank.org/BD96329D-A6E3-46C8-94A9-50C1B198BB89

The genus Ctenomys of subterranean rodents is one of the most species-rich genera of Mammalia, with 66 living species currently recognized. However, the taxonomy of the genus is dynamic with several new species and new synonymies proposed during the last decade. One of the species groups that have undergone more changes in contents in the last years is the Ctenomys mendocinus species group. Here, based on phylogenetic analysis of mitochondrial DNA sequences and qualitative and quantitative morphological evidence, we conducted an appraisal of the species richness of tuco-tucos of the C. mendocinus species group, describing two new species from west-central Argentina. The new taxa are morphometrically distinctive when compared with other geographically or phylogenetically close species of the genus, showing qualitative differences in their craniodental anatomy. One of the new species is known from the eastern Andean slopes of La Rioja and San Juan provinces, occurring on montane grasslands and shrublands above 3,500 m a.s.l., while the other is endemic of southwestern Mendoza province, occurring on montane grasslands and shrublands between 2,400–2,700 m a.s.l. In addition, we include for the first time the nominal forms C. fochi and C. validus in a phylogenetic analysis of the genus Ctenomys, showing that both correspond to the C. mendocinus species group, being the second a junior synonym of C. mendocinus. Finally, we made some comments about other candidate species within this species group as well as highlight issues that need to be addressed to gain a robust picture of the specific richness of Ctenomys.

 Andean Highlands Caviomorpha Octodontoidea species limits taxonomy tuco-tucos Universidad Nacional de Chilecito (Proyecto FICyT 2019) FONDECYT 1221115 Citation:

Teta P, Jayat JP, Alvarado-Larios R, Ojeda AA, Cuello P, D’Elía G (2023) An appraisal of the species richness of the Ctenomys mendocinus species group (Rodentia: Ctenomyidae), with the description of two new species from the Andean slopes of west-central Argentina. Vertebrate Zoo­logy 73 451–474. https://doi.org/10.3897/vz.73.e101065

 Introduction

Arguably, Rodentia is the mammalian order with the most dynamic taxonomy. New species are routinely described (e.g., Rowsey et al. 2022; Zhang et al. 2022), at the time that the taxonomic status of its numerous nominal forms are changing because new species synonyms are advanced and names traditionally viewed as synonyms are considered full species (e.g., Abreu et al. 2021; Pradhan et al. 2021). As such, the species richness of Rodentia keeps increasing, although it is still far from being well characterized (for a synthesis of current trends on rodent taxonomy see D’Elía et al. 2019).

A genus that is a good representative of the scenario above mentioned is Ctenomys de Blainville, 1826, which is one of the most diverse of the order Rodentia (D’Elía et al. 2021). Currently, it is composed of 66 known living species, which are distributed from southern Peru to the archipelago of Tierra del Fuego in southernmost Argentina and Chile (Bidau 2015). Our knowledge about the alpha taxonomy of this genus is still far from complete (D’Elía et al. 2021) and is highly dynamic, as indicated by the fact that several nominal forms have been described in the last few years (Teta and D’Elía 2020; Brook et al. 2022; Mapelli et al. 2022), others were synonymized (Parada et al. 2012; Teta et al. 2020; D’Elía et al. 2021), or suggested as candidate species (e.g., Caraballo and Rossi 2017; Tammone et al. 2021, 2022a, 2022b). As the species of Ctenomys are morphologically conservative (e.g., Fornel et al. 2018), these advances have been mostly based on integrative taxonomic approaches, using karyotypic, molecular, and morphological datasets.

Based on phylogenetic studies of mitochondrial DNA sequences and morphologic traits, species of the genus Ctenomys are grouped into nine main species groups and several species without clear phylogenetic relationships (Parada et al. 2011; De Santis et al. 2021; see also Sánchez et al. 2019; Londoño-Gaviria et al. 2019; Leipnitz et al. 2020). Among these groups, the C. mendocinus species group is widely distributed through central Argentina between the Andes and the Atlantic coast (e.g., Mapelli et al. 2017), reaching eastern Uruguay and southernmost Brazil (D’Elía et al. 1999). Karyotypic studies (e.g., Massarini et al. 1991) and phylogenetic analysis of DNA sequences (e.g., Mapelli et al. 2017) show a complex evolutionary history for the C. mendocinus species group, which reflects the difficulty to establish species limits as well as the instability in the advanced taxonomic schemes. For instance, D’Elía et al. (2021) recently synonymized C. azarae Thomas, 1903 and C. porteousi Thomas, 1919 under C. mendocinus Philippi, 1869. As currently understood, six species (i.e., C. australis Rusconi, 1934; C. bergi Thomas, 1902, C. famosus Thomas, 1920; C. flamarioni Travi, 1981; C. mendocinus; and C. rionegrensis Langguth & Abella, 1970) are included within this group (D’Elía et al. 2021; Mapelli et al. 2022), but several others are likely linked to it, at least judging by their morphology and geographic distribution (e.g., C. bonettoi Contreras & Berry, 1982; C. fochi Thomas, 1919; C. johannis Thomas, 1921, C. tulduco Thomas, 1921, and C. validus Contreras, Roig & Suzarte, 1977). The status of some of these species (e.g., C. fochi, C. johannis) is dubious as their descriptions were based on few specimens and their distinction have never been evaluated with contemporaneous approaches. Additionally, analyses of DNA sequences (Parada et al. 2011; Mapelli et al. 2017; Tammone et al. 2021, 2022a, 2022b) have identified other six candidate species within the radiation of this species group that needs to be further reviewed to corroborate or refute their distinction from other species. One of these candidate species was erroneously referred in the literature as C. fulvus Philippi, 1860 and is found at the San Guillermo National Park, in the northernmost portion of the Andes of San Juan province (cf. Haene et al. 2001; for its reference to the mendocinus group, see Borghi and Giannoni 2007). A second one was recently reported for the highland areas of western La Rioja province, being documented for the Laguna Brava area (Tammone et al. 2022a). Interestingly, these two candidate species occur in the same environment above 3,500 m a.s.l., in the Central Andean Puna ecoregion (sensu Olson et al. 2001), being separated from each other by ca. 110 km. Finally, a third one was initially reported by Mapelli et al. (2017; labeled as “Las Leñas”) and later by Tammone et al. (2021; identified as “Ctenomys sp. 3”) and is so far known from Las Leñas Valley, southwestern Mendoza province.

In this contribution, we used cytochrome b (cyt b) sequences of the mitochondrial DNA and qualitative and quantitative morphological traits of skins and skulls to evaluate the species richness of the C. mendocinus species group. We describe two new species, based on the above-mentioned candidate species. One of the new species corresponds to those populations of northernmost San Juan and western La Rioja provinces, while the other encompasses the lineage of Las Leñas, in southwestern Mendoza province. Additionally, we test the phylogenetic position of C. fochi and C. validus, suggesting that both belong to the C. mendocinus species group and the latter is a synonym of C. mendocinus.

 Materials and methods Species concept

We follow the General Lineage Species Concept, which considers that species are metapopulational lineages recognized by their emergent properties (e.g., monophyly, morphological diagnosability; de Queiroz 1998, 2007), as an ontological (i.e., primary) species concept; additionally, we framed our contribution under the so-called Phylogenetic Species Concept (PSC; sensu Cracraft 1983), which considers that species are unique evolutionary lineages which exhibit unique combinations of qualitative and quantitative traits (the smallest diagnosable clusters of samples), as an operational (i.e., secondary) species concept.

 Sampling for genetic and phylogenetic analyses

Genetic comparisons and phylogenetic analyses are based on DNA sequences of the mitochondrial cyt b gene. We used an extensive sampling of DNA sequences of specimens of the C. mendocinus species group; we included 164 sequences that were retrieved from all species belonging to the group (sensu D’Elía et al. 2021), five of the six candidate species, as well as from C. fochi and C. validus that likely belong to the group (see Supplementary Material 1). Of the sequences of the C. mendocinus species group, 17 were gathered by us as indicated below. Additionally, our sampling included sequences of each of the other 42 species of Ctenomys available in GenBank (by November 2022) plus C. pilarensis Contreras, 1993 (specimen TK66077 from the Natural Science Research Laboratory, Texas Tech University); the sequence of C. pilarensis was gathered by us (see below). This is, up to now, the phylogenetic study with the broadest specific sampling of Ctenomys. The outgroup was formed with sequences of a representative of each of the genera of Octodontidae, the sister family of Ctenomyidae, with complete sequences available in GenBank. In the light of preliminary analyses (conducted also as indicated below) we excluded three sequences downloaded from GenBank from the final analyses. Sequences MZ333073 and MZ333064 identified in GenBank as of C. azarae (a synonym of C. mendocinus; D’Elía et al. 2021) fall outside the C. mendocinus species group and related to C. talarum Thomas, 1898. These two sequences are quite similar to those of C. talarum; then considering that they were retrieved from specimens collected in Coronel Suárez (Buenos Aires, Argentina), and Arroyo Sauce Chico (Buenos Aires, Argentina), two areas where so far only C. talarum is known, they likely belong to specimens of this species. Sequence MZ333063 labeled in GenBank as C. australis falls outside the clade of the C. mendocinus species group. A close inspection of this sequence allows us to suggest that it may have some editing problems that likely affect their phylogenetic placement and it was also excluded from the analyses. Details of all sequences of the C. mendocinus species group used in the final genetic-based analyses are included in Supplementary Material 1. GenBank accession numbers of all sequences, including those of specimens that do not belong to the C. mendocinus species group, are provided in Fig. 1. Sequences acquired here (some of them from dry skins) were obtained using primers MVZ 05 and MVZ 16 (da Silva and Patton 1993) and MVZ 103 and MVZ 14 (Smith and Patton 1993) following the protocol outlined in Cadenillas and D’Elía (2021). Amplicons were purified and sequenced by Macrogen Inc., Korea. New sequences were deposited in GenBank (OQ305611–OQ305627; OQ319606).

10.3897/vz.73.e101065.figure1 63AE2611-9DD5-52D4-BC8E-0E369BE6F6AF

Maximun Likelihood tree (ln = –12720.876) obtained in the analysis of 164 cytochrome b gene sequences of the Ctenomys. Numbers indicate bootstrap (right of the diagonal) and posterior probability (left of the diagonal) values of adjacent nodes; a missing value indicates that the given node has less than 50% of posterior probability; a dash indicates that the given node was not recovered in the Bayesian analysis. For clarity the tree is split into two. In the left panel the general tree of Ctenomys is shown (outgroup not shown); species groups (sensu D’Elía et al. 2021) are indicated with bars (the two main clades of C. famosus are also labeled as in Tammone et al. 2022a). In the right panel the focus is on the Ctenomys mendocinus species group. Terminal labels indicate species name and GenBank accession numbers. For the species of the Ctenomys mendocinus species group, terminal labels include Province/State/Department and abbreviated locality (see more details in Supplementary File 1). The silhouette of Ctenomys was taken from PhyloPic and was made available by Chloé Schmidt under a license CC BY 3.0.

https://binary.pensoft.net/fig/850077 Genetic and Phylogenetic analyses

Clustal, as implemented in MEGA 6 (Tamura et al. 2013) and using the default values for all alignment parameters, was employed to perform sequence alignment. Alignment was straightforward and no adjustment by eye was needed; the alignment has no gaps. The constructed matrix was subjected to Bayesian (BA; Rannala and Yang 1996) and Maximum Likelihood (ML; Felsenstein 1981) analyses. The HKY+G+I model, selected with jModelTest (Darriba et al. 2012), was specified in both analyses. BA was performed in MrBayes 3.1 (Ronquist and Huelsenbeck 2003), by means of 2 independent runs with 3 heated and 1 cold Markov chains each. All model parameters were estimated in MrBayes; uniform interval priors were assumed for all parameters except base composition and HKY parameters, which assumed a Dirichlet process prior. Runs lasted for 10 million generations, with trees being sampled every 1,000 generations. Run convergence on a stable log-likelihood value was checked by plotting Log-likelihood values against generation time and by checking that Potential Scale Reduction Factor converged to 1. The 1st 25% of the trees sampled were discarded as burn-in; the remaining trees, sampled within the convergence zone, were used to compute a 50% majority rule consensus tree and to obtain posterior probability (PP) estimates for each clade. The ML analysis was conducted with IQ-TREE (Nguyen et al. 2015) using the online implementation W-IQ-TREE (http:/iqtree.cibiv.univie.ac.at; Trinoupoulus et al. 2016), with perturbation strength set to 0.5 and stopping rule set to 100. Clade support was calculated with 1000 ultrafast bootstrap pseudo-replications (BS; Hoang et al. 2018). The observed percentage of sequence divergence, between pairs of local samples and clades (see below), was calculated with MEGA 6 (Tamura et al. 2013) in the form of p distances ignoring those sites with missing data.

 Studied specimens in the morphological analyses

Morphological analyses of qualitative and quantitative external and cranial traits were carried out on 131 adult specimens of Ctenomys collected at 36 localities in west-central Argentina and northern Chile (Fig. 2; see Supplementary Material 2 for details). Studied specimens are housed in the following biological collections: Facultad de Ciencias Naturales e Instituto Miguel Lillo (CML; San Miguel de Tucumán, Argentina); Fundación de Historia Natural “Félix de Azara” (CFA; Ciudad Autónoma de Buenos Aires, Argentina); Instituto Argentino de Investigaciones de Zonas Áridas (CMI; Mendoza, Argentina); Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (MACN-Ma; Ciudad Autónoma de Buenos Aires, Argentina); Natural History Museum, (NHMUK; London, United Kingdom); Universidad Nacional de Río Cuarto (CUNRC; Río Cuarto, Argentina); and Universidad Austral de Chile (UACH; Valdivia, Chile). Studied specimens correspond both to species of the group of C. mendocinus (e.g., C. bergi, C. emilianus Thomas & Saint Leger, 1826, C. fochi, C. mendocinus), as well as other taxa distributed in the Andean ranges of central Argentina and Chile (e.g., C. fulvus Philippi, 1860; C. maulinus Philippi, 1872). Skins and skulls of specimens of C. coludo, C. famosus and C. knighti Thomas, 1919 were examined through photographs (Sánchez et al. 2019; SAyDS-SAREM 2019; Tammone et al. 2022a).

10.3897/vz.73.e101065.figure2 DBD88940-F06C-5C7F-B69B-97D0F521D01B

Map of central Argentina, southern Brazil and Uruguay, depicting the generalized distributional boundaries of the species and candidate species of the group of Ctenomys mendocinus. Numbers 1–10 and 11–12 correspond to the known localities for the “La Rioja-San Juan lineage,” and “Las Leñas lineage,” respectively (for reference of the numbers, see the text).

https://binary.pensoft.net/fig/850078 Anatomical descriptions and cranial measurements

Anatomical terms employed to describe external and cranial traits follow Brook et al. (2022) and De Santi et al. (2020, 2021). Fur coloration was defined following the nomenclature of Ridgway (1912). Standard external measurements were taken from field catalogs or specimen tags, including: TOTL, total length; TAIL, tail length; HFL, hind foot length (including the claw); EAR, ear length; and W, weight. Sixteen craniodental measurements were taken on each specimen with a digital caliper (nearest to 0.01 mm), following the definitions provided by Contreras and Contreras (1984). Reported measurements are: TLS, total length of the skull; CIL, condylo-incisive length; NL, nasal length; NW, nasal width; RW, rostral width; FL, frontal length; IOC, interorbital constriction; ZB, greatest zygomatic breadth; BB, braincase breadth; MB, mastoid breadth; IFH, infraorbital foramen height; DL, upper diastema length; PL, palatal length; UIW, upper incisors width; PM4L, upper fourth premolar length; and TRL, upper toothrow length.

 Morphological analyses

Morphological comparisons were guided by the results of the analyses of molecular data (see below), geography, and current taxonomy. We use descriptive statistics (i.e., mean, minimum and maximum values, standard deviation) and multivariate statistical analyses to assess the patterns of variation among lineages. Principal component analysis (PCA) was computed using sixteen craniodental measurements, all of which were previously log10 transformed. The PCA was conducted with exploratory aims in order to identify the contribution of each measurement to the total variance, extracting them from a variance-covariance matrix (Strauss 2010). Data from both males and females were pooled with the aim to obtain more robust samples for its inclusion in the statistical analyses (see Kelt and Gallardo 1994; Teta et al. 2020, Teta and D’Elía 2020). All statistical analyses were carried out with the software PAST v2.17 (Hammer et al. 2001).

 Results Phylogenetic relationships

The phylogenetic analyses strongly recovered the monophyly of Ctenomys (BS = 100; PP = 1; Fig. 1). In turn, the basal dichotomy of the clade leads on one hand to the clade formed by C. plebiscitum and C. sociabilis (BS = 100; PP = 1) and the clade formed by all other species of the genus (BS = 86; PP = 0.87). Within the latter clade, all species groups are recovered monophyletic with varying levels of support (Fig. 1). Ctenomys pilarensis falls within the C. tucumanus species group (BS = 96; PP = 1).

The clade corresponding to the C. mendocinus species group appears highly supported (BS = 99; PP = 0.91) and it is composed of 12 main lineages. The two haplotypes of C. bergi form a strongly supported clade (BS = 100; PP = 0.99), which is one of the main lineages of the C. mendocinus species group. C. flamarioni (BS = 100; PP = 1) and C. rionegrensis (BS = 100 PP = 1) also appear highly supported. Within the latter there are three main lineages; one (BS = 98; PP = 1) composed by haplotypes of Uruguayan specimens, which is sister (BS = 99; PP = 0.74) to the lineage composed by a single available haplotype from Ibicuy in southern Entre Rios province (Argentina), and the third one (BS = 99; PP = 1) composed by variants collected at two localities, Parana and Parque Nacional Pre-Delta, in west central Entre Rios province (Argentina). Average divergence value between the Uruguayan and the Ibicuy lineages is 0.13%, between the Uruguayan the Parana-Pre Delta lineages is 0.11% and between the Ibicuy and Parana-Pre Delta lineages is 0.14%. C. famosus is recovered monophyletic (BS = 97; PP = 0.99) and also shows internal geographical structure, including one clade (BS = 100; PP = 1) with haplotypes from medium elevations at the Velazco mountain chains (La Rioja) and another (BS = 99; PP = 0.95) with variants from the Famatina range (La Rioja) and Antofagasta de la Sierra (Catamarca). Average divergence value between both clades is 1.11 %. Another of the main lineages of the C. mendocinus species group is a clade (BS = 100; PP = 1) distributed in northern Neuquén and southern Mendoza provinces, that includes the haplotype of one individual of the type series of C. emilianus (see Tamonne et al. 2021). This clade is genetically homogenous (average percentage of intra clade p distance is 0.51 %) and is here tentatively referred to C. emilianus. Topotypic sequences of C. fochi form a well-supported clade (BS = 100; PP = 1) that is sister (BS = 93; PP = 0.80) to an haplotype of one individual (AO472) from Córdoba province. The latter differ on average by 1.21 % from sequences of C. fochi. Haplotypes from the nearby candidate species identified by Mapelli et al. (2017) as “Arenales” and by Parada et al. (2011) as “Tupungato” form a clade (BS = 93; PP = 0.68) that is sister (BS = 100; PP = 0.99) to the clade containing the haplotypes of C. fochi and the specimen from Córdoba. Average genetic divergence between the “Arenales-Tupungato” clade and that containing haplotypes from topotypes of C. fochi and specimen AO472 is 1.86 %. A geographically wide clade (BS = 82; PP = 0.79) is that corresponding to C. mendocinus sensu stricto; this clade shows some genealogical structure although lacks geographic structure. Haplotypes from paratypes of C. validus (OQ305615 and OQ305616) fall within the clade of C. mendocinus sensu stricto. Moreover, three haplotypes (AF370697; MZ333061, MZ333062) labeled in GenBank as C. australis also fall in the clade of C. mendocinus sensu stricto. Another main lineage (BS = 100; PP = 1) of the C. mendocinus species group is form by sequences from a specimen of Auca Mahuida in eastern Neuquén Province, referred as C. sp. 4 by Tammone et al. (2021) and three other haplotypes from two localities, General Acha and Reserva Provincial Parque Luro, from east-central La Pampa Province (labeled by Carnovale et al. 2021 as C. azarae, which is now regarded as a synonym of C. mendocinus); here, we refer to this clade as of the “Neuquén-La Pampa lineage”. Remarkably, haplotypes of other specimens collected at the two mentioned Pampean localities (see collection details in Carnovale et al. 2021: table 1) form part of the C. mendocinus s.s. clade.

Percentage of average genetic variation (p distances), based on cytochrome b sequence data, observed within and between pairs of species and candidate species (see text) of the Ctenomys mendocinus species group.

intraspecific 1 2 3 4 5 6 7 8 9 10 11
1 Arenales Tupungato 1.00
2 C. bergi 0.09 1.94
3 C. eileenae sp. nov. 0.62 3.14 2.93
4 C. emilianus 0.51 2.60 2.83 3.16
5 C. famosus 0.86 2.37 1.97 3.17 2.53
6 C. flamarioni 0.17 3.06 3.37 3.64 3.76 3.11
7 C. fochi 0.85 1.86 2.46 3.47 2.62 2.74 2.88
8 C. mendocinus 1.13 2.86 2.50 3.31 3.12 2.41 2.51 2.62
9 Neuquén-La Pampa 0.75 2.94 2.88 3.68 3.26 2.83 3.01 2.97 1.98
10 Quijadas 0.28 2.01 1.14 3.04 1.92 1.82 2.59 2.39 2.08 2.43
11 C. rionegrensis 0.64 2.50 1.68 3.49 3.24 2.33 3.36 2.80 2.69 2.81 2.09
12 C. verzi sp. nov. 0.00 2.08 1.71 2.99 2.47 1.93 2.82 2.35 2.33 2.42 1.25 2.30

Finally, there are three main lineages of the C. mendocinus species group with no available name. One of these (BS = 99; PP = 0.98) is formed by sequences retrieved from specimens from Quijadas (San Luis) which are here informally referred to, following Mapelli et al. (2017), as the “Quijadas lineage”. The second one is formed by haplotypes from specimens collected in the mountains of La Rioja and San Juan (BS = 100; PP = 1) and is here referred to as the “La Rioja-San Juan lineage”. The last one, which include the haplotypes of three individuals collected in Las Leñas, Mendoza province, form a well-supported clade (BS = 100; PP = 1) that is here referred to as “Las Leñas lineage”.

Relationships among the 12 main lineages of the C. mendocinus species group remain mostly unresolved; the single relationship that gets significant support in both analyses is that of the clade formed by C. rionegrensis and C. bergi (BS = 99; PP = 0.97). Both analyses recovered a clade formed by the “Quijadas linage”, the “Neuquén-La Pampa lineage”, C. flamarioni, and C. mendocinus sensu stricto, but it only gets significant support in the ML tree (BS = 96; PP = 0.69); the same occurs for the clade formed by the “Neuquén-La Pampa lineage”, C. flamarioni, and C. mendocinus sensu stricto (BS = 99; PP = 0.92). Another relationship observed in both analyses, but that does not get significant support in any tree (BS = 85; PP = 0.92) is that of C. flamarioni and C. mendocinus sensu stricto. Meanwhile, in the ML tree there is a clade (BS = 92) formed by C. emilianus and the “La Rioja-San Juan lineage” that is not recovered in the Bayesian tree as both lineages fall to the polytomy observed at the base of the clade corresponding to the C. mendocinus species group. Observed averages of percentage of sequence divergence between pairs of species/lineages of the C. mendocinus species group are shown in Table 1.

 Morphological variation

Qualitative morphological descriptions, including the listing of the traits that characterize each lineage, are discussed below in the context of the new species described here. Descriptive statistics for cranial measurements are provided on Table 2.

Summary statistics (mean, SD, range) of cranial measurements (in mm) of adult samples (N) of eight species of the genus Ctenomys. See Materials and Methods for abbreviations.

C. emilianus C. fochi C. fulvus C. johannis
Variable N Mean SD Min. Max. N Mean SD Min. Max. N Mean SD Min. Max. N
TLS 3 50.89 4.55 45.74 54.35 2 39.89 1.1 39.11 40.67 47 54.9 3.32 47.09 61.51 1 45.29
CIL 3 46.84 2.78 44.31 49.82 2 39.26 1.22 38.39 40.12 47 51.56 3.13 43.6 57.56 1 44.11
NL 3 17.48 0.12 17.36 17.6 2 13.16 0.78 12.61 13.71 47 18.87 1.52 15.84 21.4 1 15.33
NW 3 8.13 0.72 7.32 8.71 2 6.58 0.59 6.16 6.99 47 9.03 0.84 7.03 10.78 1 6
RW 3 11.97 1.04 10.83 12.88 2 9.15 0.49 8.8 9.5 47 13.36 1.31 10.43 15.86 1 9.49
FL 3 14.55 1.43 13.01 15.84 2 11.79 0.5 11.44 12.15 47 14.71 1.01 12.29 16.42 1 12.86
IOC 3 10.48 0.87 9.94 11.49 2 7.98 0.33 7.75 8.21 47 11.76 1.13 9.85 14.33 1 8.25
ZB 3 29.19 1.97 26.99 30.81 2 23.86 0.11 23.78 23.94 47 33.81 2.72 28.64 39.7 1 26.93
BB 3 19.92 2.77 17.18 22.72 2 16.11 0.21 15.96 16.26 47 20.72 0.8 18.73 22.46 1 18.19
MB 3 28.21 2.13 25.79 29.77 2 23.66 0.47 23.33 24 47 33.04 2.41 28.92 37.67 1 25.75
IFH 3 9.68 0.81 8.84 10.45 2 7.68 0.29 7.48 7.89 47 11.37 0.9 9.55 13.05 1 8.57
DL 3 13.46 2.26 11.45 15.9 2 10.02 0.72 9.51 10.53 47 14.46 1.24 12.14 17.25 1 12.11
PL 3 21.77 1.71 20.09 23.51 2 16.91 0.57 16.51 17.32 47 23.23 1.75 19.32 26.71 1 19.37
UIW 3 7.68 0.96 6.82 8.71 2 5.76 0.26 5.58 5.95 47 8.67 0.87 6.99 10.49 1 6.5
PM4L 3 4.18 0.46 3.68 4.6 2 3.19 0.19 3.05 3.32 47 4.26 0.21 3.63 4.71 1 3.17
TRL 3 10.88 0.69 10.14 11.51 2 8.52 0.28 8.32 8.72 47 11.44 0.57 10.02 12.82 1 8.97
C. maulinus C. mendocinus C. eileenae sp. nov. C. verzi sp. nov.
N Mean SD Min. Max. N Mean SD Min. Max. N Mean SD Min. Max. N
TLS 8 46.55 4.1 41.63 53.4 33 41.16 2.74 37.1 47.44 23 46.49 3.2 41.73 53.96 1 43.58
CIL 8 44.66 4.04 39.45 51.67 33 39.91 2.68 36.11 46.42 23 44.75 3.1 40.08 51.69 1 40.68
NL 8 16.74 1.82 14.76 19.31 33 13.67 1.12 11.74 16.92 23 16.31 1.27 14.02 19.61 1 15.2
NW 8 6.87 0.88 5.77 8.44 33 6 0.45 5.15 7.44 23 7.17 0.59 5.86 8.39 1 7.65
RW 8 10.33 1.02 8.97 12.08 33 9.34 0.9 7.91 11.3 23 10.7 0.99 9.25 12.51 1 10.26
FL 8 13.01 1.02 12.18 15.4 33 12.15 0.84 10.1 13.95 23 13.43 0.71 12.51 15.35 1 12.31
IOC 8 8.79 0.66 7.87 9.74 33 7.93 0.49 6.89 9.12 23 9.11 0.59 8.05 10.12 1 8.42
ZB 8 26.14 1.89 23.22 29.68 33 23.96 1.54 21.11 27.59 23 27.23 1.69 25.12 30.2 1 25.04
BB 8 17.01 0.61 16.01 17.67 33 16.81 1.25 15.16 22.33 23 18.53 0.6 17.66 19.69 1 17.76
MB 8 23.84 2.3 21.43 28.84 33 23.75 1.4 20.04 26.63 23 27.03 1.43 24.95 29.51 1 23.36
IFH 8 9.34 0.72 8.07 10.12 33 7.47 0.56 6.41 9.07 23 8.74 0.77 7.78 10.67 1 8.33
DL 8 13.04 1.57 10.9 15.83 33 10.38 1.15 7.49 12.97 23 11.71 0.98 10.33 14.29 1 10.98
PL 8 20.71 2.09 18.16 24.48 33 17.54 1.46 15.2 20.67 23 19.01 1.66 17.16 22.7 1 18.2
UIW 8 6.92 0.69 6.03 7.99 33 5.99 0.6 5.18 7.43 23 6.79 0.68 5.61 8.3 1 6.58
PM4L 8 3.77 0.25 3.52 4.26 33 3.29 0.18 2.85 3.66 23 3.44 0.19 3.19 3.86 1 3.67
TRL 8 9.97 0.88 8.94 11.4 33 8.64 0.5 7.61 9.78 23 9.3 0.67 8.25 10.44 1 8.82

The first two principal components (PCs) together accounted for 94.8% of the total variance (Fig. 3; Table 3). PCA revealed that all variables were positively correlated with the PC1 (93.3% of the total variance), suggesting that it mostly corresponds to a vector of size. Plots of individual scores shows that C. bergi, C. mendocinus (including C. validus), the “La Rioja-San Juan lineage”, and C. fulvus mostly segregate along PC1 from lower to higher values, while the latter three occupy similar range values along PC2. C. emilianus partially overlaps with C. fulvus and the “La Rioja-San Juan lineage.” C. fochi and C. johannis were included within the polygon of C. mendocinus. The “Las Leñas lineage” is placed in an intermediate position between C. mendocinus and the “La Rioja-San Juan lineage”. Secondarily, C. maulinus was segregated from all other taxa along the second axis as it occupies lower values on this PC. Highest absolute loadings on PC1 corresponded to variables IFH, UIW and NW, while for the PC2 were DL, IOC and MB (Fig. 3; Table 3).

10.3897/vz.73.e101065.figure3 A1BCCA94-8A65-5D77-812E-212BB37FF16E

Individual scores of adult specimens of Ctenomys from west-central Argentina (n = 131) for: principal components 1 and 2. Abbreviations are as follow: be, C. bergi; em, C. emilianus (= Central Clade of Tammone et al. 2021); fo, C. fochi; fu, C. fulvus; jo, C. johannis; ma, C. maulinus; me, C. mendocinus (two paratypes of C. validus are depicted with a “va”); lrsj, La Rioja-San Juan lineage; ll, Las Leñas lineage.

https://binary.pensoft.net/fig/850079

Results of principal components analysis performed on adult specimens of four species of Ctenomys (n = 119). See Materials and Methods for explanation of abbreviations.

PC 1 PC 2
TLS 0.2324 –0.0963
CIL 0.2132 –0.1464
NL 0.2506 –0.2531
NW 0.2935 0.3054
RW 0.2851 –0.0510
FL 0.1538 0.2413
IOC 0.2812 0.4107
ZB 0.2621 0.1298
BB 0.1597 0.3209
MB 0.2491 0.3616
IFH 0.3117 –0.0821
DL 0.2699 –0.4170
PL 0.2399 –0.3539
UIW 0.2962 –0.0848
PM4L 0.2081 –0.1377
TRL 0.2274 –0.1857
% variance 93.25 1.54
Eigenvalue 0.0816 0.0014
Discussion

Taken together, the molecular and morphological results provide strong evidence that the current taxonomic scheme does not reflect the species richness of the Ctenomys mendocinus species group. While one currently recognized species, C. validus, is not distinguishable from C. mendocinus, there are two molecular lineages (i.e., those here referred to as “La Rioja-San Juan” and “Las Leñas”) that are also morphologically distinct from all other species of the group. As no names are available for them, we named and described them below. First, we erect a new species based on the “La Rioja-San Juan lineage” and then one based on the “Las Leñas lineage.” A third candidate species, the “Quijadas lineage”, remains awaiting a morphological and/or nuclear DNA evaluation of its distinction.

Contrary to the “La Rioja-San Juan lineage,” which is formalized below as a new species based on a large sample of individuals, the “Las Leñas lineage” is formalized as a new species on the base of morphological and genetic data of just one and three specimens, respectively. Descriptions based on one or few specimens are problematic, mainly because intraspecific variation, including sexual dimorphism and ontogenic changes, is poorly assessed. However, there are several recent examples of descriptions of new mammal species based on only one specimen, even within diverse and cryptic groups such as rodents (e.g., Teta et al. 2022). Under certain circumstances, and with some precautions, descriptions based on small samples of specimens can be well justified (e.g., Guayasamin et al. 2018). For instance, Köhler and Padial (2016) expressed that the advantage of recognizing well-supported lineages as targets for further research and conservation, even when based on limited samples, greatly surpasses the possible inconveniences of naming them. In order to minimize the possibility of taxonomic errors, we follow Guayasamin et al. (2018), which provided a brief guide to describe species based on single (or few) specimens. Thus, beyond the congruence between our morphological and molecular datasets, that clearly shown the distinction of the species here described, we construct the morphological diagnosis based on traits that present low intraspecific variation (e.g., size and shape of incisive foramina and tympanic bullae), and use well preserved specimens with precise collection locality data.

Animalia Rodentia Ctenomyidae C18217CF-1475-526F-8687-E0952D728BBD Ctenomys eileenae https://zoobank.org/F1355C16-11F3-40C9-8E40-3C90EEE2C2F9 sp. nov. Figs 4 , 5 , 6 , 7 , 8 Ctenomys fulvus – Haene et al. (2001: 63) Ctenomys sp. 1 – Borghi and Giannoni (2007:158) Ctenomys sp. (Laguna Brava) – Tammone et al. (2022a: 5) Eileen’s tuco-tuco Tuco-Tuco de Eileen Holotype.

An adult male (MACN-Ma 30847), including skin, skeleton, and tissues, collected on 14 May 2022 by J. P. Jayat (original field number JPJ 2821) (Figs 4–6). An 801 base-pair sequence of the cyt b gene has been deposited in GenBank with accession number OQ305623.

10.3897/vz.73.e101065.figure4 9C0725B3-9986-5F43-809F-A5F0716EA790

Dorsal (A) and ventral (B) views of the external appearance of the holotype of C. eileenaesp. nov. (MACN-Ma 30847).

https://binary.pensoft.net/fig/850080 10.3897/vz.73.e101065.figure5 E027F2DA-CA10-5C40-A20C-EB9C2C5981EC

Lateral (above), dorsal (below, left) and ventral (below, right) views of the skull and labial view of the mandible (middle) of the holotype of C. eileenaesp. nov. (MACN-Ma 30847). Scale = 5 mm.

https://binary.pensoft.net/fig/850081 10.3897/vz.73.e101065.figure6 F8B51C34-8D79-537A-B101-5EDFE42F4852

Ventral view of the incisive and interpremaxillary foramina in six species of Ctenomys from west-central Argentina: AC. johannis (CFA-Ma 12452); BC. maulinus (FMNH 23215); CC. mendocinus (CMI 2497); DC. pontifex (BM 60.5.1.2; holotype); EC. eileenaesp. nov. (MACN-Ma 30847; holotype); and FC. verzisp. nov. (CMI 7703; holotype). Specimens are scaled to the same length.

https://binary.pensoft.net/fig/850097 Type locality.

Argentina: La Rioja Province, Vinchina Department, Refugio El Peñón, on road to Laguna Brava, 3,609 m a.s.l. (–28.4765°, –68.8376°; Fig. 2: locality 1).

 Measurements of the holotype (in mm).

TOTL, 285; TAIL, 88; HFL, 44; EAR, 8; TLS, 49.68; CIL, 48.17; NL, 17.04; NW, 7.86; FL, 14.21; RW, 12.03; ZB, 29.90; IOB, 10.00; BB, 19.40; MB, 29.41; IFH, 9.92; DL, 12.62; PL, 21.68; UIW, 7.65; PM4L, 3.67; TRL, 10.44. Weight, 275 g.

 Paratypes.

Three specimens as follows. An adult female (MACN-Ma 30846), including skin, skeleton, and tissues, collected on 2 October 2021 by J. P. Jayat (original field number JPJ 2762) at the species type locality; an 801 base-pair sequence of the cyt b gene of this specimen has been deposited in GenBank with accession number OQ305626. A young female (MACN-Ma 30848), including skin, skeleton, and tissues, collected on 16 May 2022 by J. P. Jayat (original field number JPJ 2871) at the species type locality; an 801 base-pair sequence of the cyt b gene of this specimen has been deposited in GenBank with accession number OQ305624. An adult female (MACN-Ma 30849), including skin, skeleton, and tissues, collected on 17 May 2022 by J. P. Jayat (original field number JPJ 2884) at the species type locality; an 801 base-pair sequence of the cyt b gene of this specimen has been deposited in GenBank with accession number OQ305625. See Supplementary Material 3 for measurements of the paratypes.

 Other examined specimens.

Argentina: La Rioja Province: Laguna Brava (CFA 12410, CFA 12411, CFA 12412 [Fig. 2, locality 1]). San Juan Province: Parque Nacional San Guillermo, without precise locality (CML 430, CML 772); Parque Nacional San Guillermo, Cerro Agua del Indio (MACN-Ma 18820, MACN-Ma 18821, MACN-Ma 18823 [Fig. 2, locality 2]); Parque Nacional San Guillermo, Cerro Imán (MACN-Ma 18817, MACN-Ma 18819, MACN-Ma 18828 [Fig. 2, locality 3]); Parque Nacional San Guillermo, Los Caserones (MACN-Ma 18816, MACN-Ma 18818 [Fig. 2, locality 4]); Parque Nacional San Guillermo, Mina La Brea (MACN-Ma 18824; [Fig. 2, locality 5]); Parque Nacional San Guillermo, Puesto Agua del Godo (MACN-Ma 18813, MACN-Ma 18814, MACN-Ma 18815 [Fig. 2, locality 6]); Parque Nacional San Guillermo, Refugio del Macho Muerto (MACN-Ma 18825; [Fig. 2, locality 7]); Parque Nacional San Guillermo, Rincón del Río (MACN-Ma 18826, MACN-Ma 18827 [Fig. 2, locality 8]); Parque Nacional San Guillermo, Vega Agua del Godo (CML 430, CML 1916 [Fig. 2, locality 9]); Parque Nacional San Guillermo, Vega del Infiernillo (MACN-Ma 18822 [Fig. 2, locality 10]).

 Morphological diagnosis.

A large-sized tuco-tuco of the C. mendocinus species group (TOTL, 244–289 mm; TAIL, 66–100 mm; HFL, 32–44 mm; EAR, 6–10 mm; W, 100–326 g), with moderately differentiated dorsal and ventral coloration; dorsum Dresden brown to Saccardo’s olive, tinged with cinnamon brown in some individuals, becoming deep olive buff to olive buff on venter. Skull strongly built, slightly larger and robust than in other species of this group, and with a proportionally broader and shorter rostrum; zygomatic arches robust and with a rounded outline in dorsal view; edges of frontals posterior to the interorbital constriction moderately divergent; postorbital processes of frontals moderately to well developed; premaxillo-frontal suture at the level of the naso-frontal suture; incisive foramina large and conspicuously broad, recessed in a common fossa of rhomboidal outer borders and completely separated by a bony septum; interpremaxillary foramen small; auditory bullae inflated and ovate; incisors orthodont.

 Morphological description.

Pelage dense, fine, and soft, about 20–22 mm long over back and rump; dorsum with fur ranging from Dresden brown to Saccardo’s olive; individual hairs dark neutral gray colored, except for their distal thirds, which are buffy. Some individuals have the nose, crown and the dorsal midline tinged with cinnamon brown; others have the nose and crown mummy brown. Color of ventral pelage olive buff or buffy brown, with the line separating from dorsum indistinct; individual hairs dark gray basally, with distal tips whitish, olive buff or buffy brown. Fur of fore and hind limbs colored like dorsum, except internal sides which are pale olive buff. Top of manus and feet covered with brownish hairs. Mystacial vibrissae surpassing the dorsal edge of the pinnae when laid back alongside of head; superciliary vibrissae sparse, extending to the base of the pinnae when laid back alongside of head. Ears sparsely covered with short, brownish hairs. Pes broad, all digits with ungueal tufts of stiff bristles, and strong claws. Tail short (40–51% of the head and body length), slightly darker above than below and sparsely covered by short buffy hairs; its distal third is covered by a dorsal fringe of dark brown, longer hairs (Fig. 4).

Skull strongly built and robust, with a proportionally broader and shorter rostrum and zygomatic arches broad and nearly rounded in dorsal view (Fig. 5). Nasals moderately bowed, long and narrow, with their broadest portion placed to the anterior third and with nearly straight to convex lateral margins; the anterior tips of nasals are in front of the level of the anterior end of upper diastema. Premaxillo-frontal suture placed in line with the naso-frontal suture. Supraorbital borders well defined, with moderately to well-developed postorbitary processes on frontals. Persistent interfrontal fontanelles variably present. Interparietal large and narrow. Temporal ridges moderately developed in adult specimens. Lambdoid crest well developed. Rostral masseteric fossa dorsal to alveolar sheath of the I1, deep and ending in a curved crest slightly anterior to or level with premaxillary-maxillary suture. Zygomatic arch broad, with well-developed postorbital processes of jugal and a conspicuous lateral masseteric fossa. Incisive foramina large and conspicuously broad, recessed in a common fossa of rhomboidal outer borders (Fig. 6); interpremaxillary foramen small to well developed, although always evident. Palatal bridge with two major palatine foramina at about level of M1. Mesopterygoid fossae “V” shaped, reaching anteriorly the posterior portion of M2 (Fig. 5). Alisphenoid-basisphenoid bridge broad; bony roof of mesopterygoid fossa with two medium-sized and nearly pyriform sphenopalatine vacuities. Buccinator-masticatory foramen large, and divided in some individuals. Paraoccipital processes well developed, broad and comma-shaped. Auditory bullae well inflated and oval, with salient auditory tubes.

Mandible robust and markedly hystricognathous, with coronoid process long and pointed (Fig. 5). Condyloid process robust, bearing a well-developed articulation flange. Postcondyloid process with a small ventrolateral apophysis. Masseteric crest nearly horizontal. Chin process well developed and visible in lateral view, located at the level of the p4. The bottom of the alveolar sheath of p4 does not protrude much (Fig. 5).

Upper incisors large, moderately robust, and nearly orthodont; frontal enamel surface orange. Maxillary tooth rows slightly divergent posteriad. M3 reduced (Fig. 5).

Descriptive statistics for external and cranial measurements are provided on Table 2; individual measurements are given on Supplementary Material 2 and 3.

 Distribution.

Known from several localities above 3,500 m a.s.l. in western La Rioja and northernmost San Juan provinces, west-central Argentina (Fig. 2).

 Etymology.

We named this species in honor of Eileen Lacey, a North American biologist devoted to studying the evolution of behavioral diversity of mammals. Among others, the studies of Eileen have focused on subterranean rodents of the genus Ctenomys. Eileen is the current president of the International Federation of Mammalogists. The species name is a patronym in the genitive singular.

 Comparisons.

Ctenomys eileenaesp. nov. differs from C. bergi, C. fochi, C. johannis, C. mendocinus, and C. tulduco by its larger size (TLS = 41.7–53.9 vs. 37.4–44.7 mm), proportionally shorter nasals, lesser globose tympanic bullae, and proportionally wider and longer incisive foramina (Figs 6–8). Furthermore, the postorbital processes in Ctenomys eileenaesp. nov. are moderately to well developed, while in C. bergi, C. fochi, C. johannis, C. mendocinus, and C. tulduco are absent to slightly expressed.

10.3897/vz.73.e101065.figure7 B88432E7-28FE-5F1E-92CF-BB5B18F90006

Dorsal (A–E) and ventral (F–J) views of the skulls in five species of Ctenomys from west-central Argentina and northern Chile: A, FC. knighti (NHMUK 1919.2.7.41); B, GC. johannis (CFA-MA 12452); C, HC. fulvus (UACH 309); D, IC. mendocinus (CMI 2497); and E, JC. eileenaesp. nov. (MACN-Ma 30846). Scale = 5 mm.

https://binary.pensoft.net/fig/850082 10.3897/vz.73.e101065.figure8 5D6B90DA-BA67-510B-A75C-397774630EF4

Selected differences comparing the cranial anatomy of Ctenomys eileenaesp. nov. (MACN-Ma 30846) and other Ctenomys species including C. johannis (CFA-MA 12452), and C. knighti (NHMUK 1919.2.7.41). Note that C. eileenae has proportionally shorter nasals (n) and much larger and broader incisive foramina (if) than C. johannis and narrower upper incisors (ui), posteriorly displaced postorbitary process (pp), larger and broader incisive foramina, and more inflated tympanic bullae (tb) than C. knighti. Specimens are scaled to the same length.

https://binary.pensoft.net/fig/850083

Ctenomys eileenaesp. nov. can be differentiated from C. coludo and C. famosus by its larger size and more robust appearance, less inflated tympanic bullae and the presence of interparietal bone (cf. Thomas 1920a, 1920b). In addition, Ctenomys eileenaesp. nov. has moderately to well-developed postorbital processes, while in C. coludo and C. famosus this structure is mostly absent.

Ctenomys eileenaesp. nov. differs from C. emilianus (Fig. 9) by its more robust appearance, more developed postorbital process, and proportionally larger and broader incisive foramina. C. eileenaesp. nov. also has a moderately large interparietal bone, while in C. emilianus this bone is usually absent (when present is small).

10.3897/vz.73.e101065.figure9 D8496823-C562-5AC3-B7DC-C5E3DA68DE3C

Dorsal (A–E) and ventral (F–J) views of the skulls in five species of Ctenomys from west-central Argentina: A, FC. emilianus (CMI 7701); B, GC. maulinus (CMI 3800); C, HC. mendocinus (CMI 2497); D, IC. pontifex (NHMUK 60.5.1.2; holotype); and E, JC. verzisp. nov. (CMI 7703). Scale = 5 mm.

https://binary.pensoft.net/fig/850084

Ctenomys eileenaesp. nov. differs from C. fulvus, which is endemic from northern Chile, by its much smaller size (TLS = 41.7–53.9 vs. 47.1–61.5 mm), narrower and less quadrate interorbital region, and proportionally narrower rostra and upper incisors (Fig. 7). In addition, Ctenomys eileenaesp. nov. has proportionally broader incisive foramina.

Ctenomys eileenaesp. nov. can be differentiated from C. knighti by its much narrower upper incisors, proportionally wider incisive foramina, smaller and lesser globose tympanic bullae, and less quadrate interorbital region, with posteriorly placed postorbitary processes on frontals (vs. anteriorly placed in C. knighti) (Fig. 7 and 8).

Ctenomys eileenaesp. nov. can be differentiated from C. verzisp. nov. by its larger size (TLS = 41.7–53.9 vs. 43.6 mm) and more robust appearance, and by its proportionally broader and shorter incisive foramina. Also, Ctenomys eileenaesp. nov. has moderately to well-developed postorbital processes, while in C. verzisp. nov. these structures are absent.

Pairwise genetic distances with other species of the Ctenomys mendocinus species group range from 2.93 to 3.68 % (Table 1).

 Natural history.

Mostly unknown; all known recording localities of Eileen’s tuco-tuco lay within the Central Andean Puna ecoregion. The flora in this area is characterized by montane shrublands, cushion plants, and grasslands. In the area of El Peñón, individuals of this new species were captured both on humid and organic soils of the “vegas” and in more dry and rocky grounds bordering these “vegas”. In the “vegas” vegetation type (areas of streams and river plains), the dominant plant types are Festuca, Poa, and Cinnagrostis. The more xeric microhabitats in this area are found on dry slopes and plateaus, the dominant species are saltbush (Ephedra), Lycium (Solanaceae) and Senecio (Asteraceae). One female captured in this locality in October 2021 was pregnant, but two females and one male were not sexually active in May 2022. The two females collected in October 2022 were molting. Other small mammals collected in El Peñón, near the new species of Ctenomys, included Abrothrix andina (Philippi, 1858), Akodon spegazzinii Thomas, 1897, and Phyllotis vaccarum Thomas, 1912.

 Conservation.

Ctenomys eileenaesp. nov. is distributed over an area of ca. 900 km2 in western La Rioja and northernmost San Juan provinces, west-central Argentina (Fig. 2). More than a half of its known distribution is included within the Parque Nacional San Guillermo, one of the few areas with effective protection in the central Andes of Argentina. Although the species does not seem to be threatened, being even locally abundant in some areas (e.g., in the vicinity of Laguna Brava), its restricted distribution, in an environment that suffers various anthropogenic pressures (e.g., megamining, cattle ranching), invites a careful review of its conservation status.

 Animalia Rodentia Ctenomyidae 947E0BB4-AA2C-5F97-A0D5-0F568FCF91AE Ctenomys verzi https://zoobank.org/935F6E2F-0B11-40E5-98A4-ECB57F73E160 sp. nov. Figs 6 , 9 , 10 , 11 , 12 Ctenomys sp. Las Leñas – Mapelli et al. (2017: 133) Ctenomys sp. 3 – Tammone et al. (2021: 1407) Verzi’s tuco-tuco Tuco-Tuco de Verzi Holotype.

CMI 7703, adult male; skin, skull, and partial skeleton collected on 27 March 2008 by Pablo Cuello (original field number PC06) (Figs 6, 9–12). An 801 base-pair sequence of the cyt b gene has been deposited in GenBank with accession number OQ305620.

 Type locality.

Argentina: Mendoza Province, Malargüe Department, 10 km by road NW Las Leñas, 2,799 m a.s.l. (–35.0973°, –70.1363°; Fig. 2: locality 11).

 Measurements of the holotype (in mm).

TOTL, 260; TAIL, 89; HFL, 40; EAR, 7; TLS, 43.58; CIL, 40.68; NL, 15.20; NW, 7.65; FL, 12.31; RW, 10.26; ZB, 25.04; IOB, 8.42; BB, 17.76; MB, 23.36; IFH, 8.33; DL, 10.98; UIW, 6.58; PL, 18.20; PM4L, 3.67; TRL, 8.82.

 Morphological diagnosis.

A medium-sized tuco-tuco of the C. mendocinus species group, with dorsal and ventral coloration well differentiated; dorsum light brownish olive, becoming deep olive-buff on flanks; venter olive-buff, with the line separating from dorsum moderately defined. Skull moderately robust, with rostrum proportionally short and broad and interorbital region with posteriorly divergent outer margins; zygomatic arch relatively broad, with well-developed postorbital processes of jugal and a conspicuous lateral masseteric fossa; dorsal profile of the cranium with a marked inflection downwards at the parietal-occipital region; incisive foramina moderately long and broad, recessed in a common fossa of nearly straight outer borders; interpremaxillary foramen moderately large; sphenopalatine vacuities large; auditory bullae moderately inflated, and pyrifom.

 Morphological description.

Pelage dense, fine, and soft, about 10–12 mm long over back and rump; dorsum with fur light brownish olive, becoming deep olive-buff on flanks; individual hairs dark neutral gray colored, except for the distal tips, which are lighter. Nose brownish olive. Color of ventral pelage olive buff, with the line separating from dorsum moderately defined; individual hairs dark gray basally, with distal tips whitish to olive buff. Fur of fore and hind limbs colored like dorsum, except for their internal sides which are lighter. Mystacial vibrissae surpassing the dorsal edge of the pinnae when laid back alongside of head; superciliary vibrissae sparse, extending to the base of the pinnae when laid back alongside of head. Ears sparsely covered with short, brownish olive hairs. Manus covered by silvery to brownish hairs, with long claws (ca. 11 mm in the third digit). Pes broad and dorsally covered by silvery to brownish hairs; all digits with ungueal tufts of stiff bristles, and strong claws. Tail short (ca. 52% of the head and body length), darker above than below and sparsely covered by short hairs (Fig. 10).

10.3897/vz.73.e101065.figure10 8CEB4A70-4207-558A-92E2-F07F684D8126

Dorsal (A) and ventral (B) views of the skin of the holotype of C. verzisp. nov. (CMI 7703). Scale = 10 mm.

https://binary.pensoft.net/fig/850085

Skull moderately robust, with rostrum proportionally short and broad, interorbital region with posteriorly divergent outer margins, and zygomatic arches broad and nearly parallel-sided in dorsal view (Fig. 11). Nasals relatively flat, moderately long and narrow, broadest anteriorly, and with nearly straight lateral margins; their anterior tips are in line to the level of the anterior end of upper diastema. Premaxillary-frontal suture in line with the naso-frontal suture. Supraorbital ridges well defined, without postorbital processes on frontals. Interparietal completely fused. Temporal ridges not developed. Lambdoid crest slightly developed. Rostral masseteric fossa dorsal to alveolar sheath of the I1, deep and ending in a curved crest slightly anterior to or level with premaxillary-maxillary suture. Bottom of the alveolar sheaths of the upper incisors are visible laterally and located at the level of DP4. Zygomatic arch broad, with well developed postorbital processes of jugal and a conspicuous lateral masseteric fossa. Dorsal profile of cranium with a marked inflection downwards in the parietal-occipital region. Incisive foramina moderately long and broad, recessed in a common fossa of nearly straight outer borders; interpremaxillary foramen moderately large (Fig. 6). Palatal bridge with two major palatine foramina at about level of M1. Mesopterygoid fossa “V” shaped, reaching anteriorly the middle portion of M2. Alisphenoid-basisphenoid bridge thin; bony roof of mesopterygoid fossa with two large and nearly pyriform sphenopalatine vacuities. Buccinator-masticatory foramen large and divided. Paraoccipital processes well developed and comma-shaped. Auditory bullae moderately inflated and pyrifom, with salient auditory tubes (Fig. 11).

10.3897/vz.73.e101065.figure11 0AB779CC-190A-5C75-B4A2-95E4B9B0D4C8

Lateral (above), dorsal (below, left) and ventral (below, right) views of the skull and labial view of the mandible (middle) of the holotype of C. verzisp. nov. (CMI 7703). Scale = 5 mm.

https://binary.pensoft.net/fig/850086

Mandible robust and markedly hystricognathous, with coronoid process long and pointed; condyloid process robust, bearing a poorly developed articulation flange. Postcondyloid process with a small ventrolateral apophysis. Chin process poorly developed and moderately visible in lateral view; bottom of alveolar sheath of p4 does not protrude much (Fig. 11).

Upper incisors large, moderately robust, and nearly orthodont; frontal enamel surface orange. Maxillary tooth rows slightly divergent posteriad. M3 reduced, with the posterolingual face flat and an anterior lobe protruding (Fig. 11).

 Distribution.

Only known from the type locality (see above) and its surroundings (RP22, 5.8 km N de Las Leñas; see Tammone et al. 2021; Fig. 2, locality 12), at the Andes of southwestern Mendoza in west-central Argentina (Fig. 2; localities 11–12). The only two known localities are separated by less than 3.2 km.

 Etymology.

We named this species in honor of Diego Verzi, an Argentinean mammalogist and paleontologist devoted to the study of mammal evolution and systematics. Diego has a large publication record on living and fossil octodontoid rodents, including ctenomyids. The species name is constructed as a noun in apposition based on the name of a man.

 Comparisons.

Ctenomys verzisp. nov. can be differentiated from C. johannis and C. mendocinus by its less globose tympanic bullae, absence of interparietal bone and larger incisive foramina (Figs 9, 12). Additionally, the tympanic bullae are not visible from above in Ctenomys verzisp. nov., while they visible in dorsal view in both C. johannis and C. mendocinus (Fig. 12).

10.3897/vz.73.e101065.figure12 76D5938F-8F1B-503B-BBDA-3A9EC4B303AB

Selected differences comparing the cranial anatomy of Ctenomys verzisp. nov. (CMI 7703) and other Ctenomys species including C. johannis (CFA-MA 12452), and C. mendocinus (CMI 2497). Note that C. verzisp. nov. lacks interparietal (ip), has proportionally larger and broader incisive foramina (if), and smaller and not visible from above tympanic bullae (tb). Specimens are scaled to the same length.

https://binary.pensoft.net/fig/850087

Ctenomys verzisp. nov. can be differentiated from Ctenomys eileenaesp. nov. by its smaller size (TLS = 43.6 vs. 41.7–53.9 mm), less robust appearance, and by its proportionally more narrow and larger incisive foramina. In addition, the skull of Ctenomys verzisp. nov. lacks postorbital processes, while these structures are moderately to well developed in Ctenomys eileenaesp. nov.

Ctenomys verzisp. nov. differs from C. emilianus by its smaller size (TLS = 43.6 vs. 45.7–54.3 mm) and less robust appearance, smaller sphenopalatine vacuities, and less proodont upper incisors (Fig. 9). In addition, the interpremaxillary foramen is large and closely placed to the incisive foramina in Ctenomys verzisp. nov. and large but well separated from the incisive foramina in the C. emilianus (Fig. 6).

Ctenomys verzisp. nov. differs from C. maulinus by its smaller size (TLS = 43.6 vs. 41.6–53.4 mm) and less robust appearance, smaller sphenopalatine vacuities, more pyriform tympanic bullae, and proportionally longer incisive foramina. In addition, the interpremaxillary foramen is large and closely placed to the incisive foramina in Ctenomys verzisp. nov. and large but well separated from the incisive foramina in C. maulinus (Fig. 9).

Ctenomys verzisp. nov. differs from C. pontifex by its more pyriform tympanic bullae (vs. narrow and nearly tubular in C. pontifex), shorter rostrum, and proportionally longer incisive foramina (Fig. 6). Also, in Ctenomys verzi the premaxillofrontal suture lies at the same line of the nasofrontal suture, while in C. maulinus the former is extended behind the second (Fig. 9).

Pairwise genetic distances with other species of the Ctenomys mendocinus species group range from 1.25 to 2.99 % (Table 1).

 Natural history.

Mostly unknown; the two known localities for this species are placed within the same valley, at 2,400–2,700 m a.s.l. The landscape in this area corresponds to the Southern Andean Steppe ecoregion, which is characterized by montane shrublands and grasslands. Most plants between 1,900 to 2,700 m a.s.l. correspond to the genera Stipa, Adesmia, Mulinum, Nassauvia, and Chuquiraga. The climate is cold and desert, with most precipitation and snow falling during winter. Other small mammals collected in Las Leñas, syntopically with the new species, included Abrothrix hirta (Thomas, 1895), A. olivacea (Waterhouse, 1837), Euneomys chinchilloides (Waterhouse, 1839), E. fossor (Thomas, 1899), Loxodontomys micropus (Waterhouse, 1837), Paynomys macronyx (Thomas, 1894), and Phyllotis pehuenche Jayat et al., 2022.

 Conservation.

As currently defined, Verzi’s tuco-tuco has a small geographic range, which constitutes a proxy of its conservation status (Bidau et al. 2012; Caraballo et al. 2023). Most other species of tuco-tucos with restricted ranges were traditionally referred to as Data Deficient (DD; see SAREM-MAyDS 2019; but see Caraballo et al. 2023). However, the use of this category (DD) is not exempt of inconveniences; overall, it is uninformative as species may be categorized as such for different reasons, limiting the chances to enact conservation measures or to support additional scientific investigation on these taxa (see Teta et al., 2021). Taking into account that the new species is only known from two localities, its consideration as endangered or vulnerable seems to be more appropriate. This situation could be aggravated by tourism and the infrastructure associated with this activity, as in this valley (Las Leñas) occurs one of the largest Argentinian sky centers, being visited each year by numerous people. Additional surveys are much needed to evaluate more accurately its conservation status.

 Final Remarks

The description of two new species of Ctenomys is not unexpected; in fact, the use of integrative approaches, coupled with specimen collection in non-sampled areas and the assessment of specimens already housed in biological collections, resulted in the recognition of 9 new living species in this genus during the last 10 years (e.g., Gardner et al. 2014; Brook et al. 2022; Mappeli et al. 2022). The wide identification of several other candidate species suggests that more new species of Ctenomys will be discovered and described in the near future. At the same time, other nominal forms have been recently synonymized as a result of taxonomic efforts (e.g., Teta et al. 2020; Teta and D’Elía 2020; D’Elía et al. 2021). Additionally, several species have been recently included in phylogenetic analyses, allowing the clarification of their placement within the radiation of Ctenomys (e.g., Sánchez et al. 2019; Londoño-Gaviria et al. 2019). In this regard, our analysis indicates that C. pilarensis is a member of the C. tucumanus species group, corroborating an early result, based on a short DNA fragment and a narrow taxonomic sampling, presented by Mascheratti et al. (2000). One of the species groups that have undergone more changes in the last decade is the C. mendocinus species group, which is the group to which belong the two new species described here. The analysis of qualitative and quantitative character traits strongly suggests that the species described here are distinguishable from other closely distributed or phylogenetically related taxa. Within the group of C. mendocinus, C. eileenaesp. nov. is proportionally larger and more robust (see comparisons above), inhabiting in a higher altitudinal range than other taxa of this group (> 3,500 m a.s.l.). Additionally, both morphological and molecular evidence clearly separates it from C. fulvus, which belongs to the C. fulvus species group. Finally, we also ruled out a possible conspecificity between C. eileenaesp. nov. and C. knighti, as was suggested by Tammone et al. (2022a), since both species depict largely distinct cranial morphologies (see comparisons above). Similarly, C. verzisp. nov. has a unique combination of character traits, including a moderately robust skull with a markedly inflected dorsal profile at the parietal-occipital region; moderately long and broad incisive foramina and moderately inflated and pyriform auditory bullae. Additionally, the morphological and molecular evidence clearly separates it from C. maulinus and C. pontifex, other two species distributed in nearby Andean regions.

In addition to providing evidence for the existence of the new species described above, our results are relevant for other aspects of the specific diversity of the C. mendocinus species group. These issues include the suggestion of a novel synonymy (i.e., C. validus under C. mendocinus; see discussion below), the inclusion of a species in the species group (i.e, C. fochi), as well as the corroboration of the existence of other candidate species whose distinction needs to be further evaluated (see discussion below).

Two haplotypes recovered from paratype specimens of C. validus are part of the clade corresponding to C. mendocinus sensu stricto; moreover, they fall in a subclade with an haplotype of a topotype of C. mendocinus. Previous studies, based on multivariate statistical analysis of cranial measurements, also suggest a close similarity between topotypical samples of C. validus and C. mendocinus (Rosi et al. 1992). The only two specimens of C. validus that we studied are slightly larger than those analyzed belonging to C. mendocinus (cf. Fig. 3); however, we were unable to find qualitative craniodental differences between C. validus (see Supplementary Material 4) and C. mendocinus, despite some minor distinction in their external coloration (i.e., studied specimens of C. validus have a conspicuous collar of whitish hairs). Together, the molecular and morphological evidence allows us to formally suggest that C. validus is a synonym of C. mendocinus; this taxonomic hypothesis should be tested with the analysis of nuclear DNA sequences.

Although we lack DNA sequences for specimens indisputably assignable to C. johannis, both the original description and the examination of one topotype of this nominal form, allow us to hypothesize that C. johannis is also a synonym of C. mendocinus or at least a closely related cryptic species (see also Fig. 3). In fact, we were unable to find qualitative or quantitative differences between them; both taxa are characterized by relatively globose, well visible in dorsal view, tympanic bullae, and have proportionally short and broad incisive foramina (cf. Fig. 12).

In a novel result of this study, the phylogenetic analysis of mitochondrial DNA sequences placed haplotypes of two topotypes of C. fochi within the clade of the C. mendocinus species group, indicating that C. fochi is a member of this species group. Interestingly, sister to the clade formed by sequences of C. fochi appears the sequence of one individual (AO472) from Córdoba province. The latter differs on average by 1.21 % from topotypic sequences of C. fochi, a value that is observed in intraspecific comparisons of Ctenomys (e.g., Londoño-Gaviria et al. 2019; Teta et al. 2020). Considering this and based on its overall cranial morphology (see Supplementary Material 4), we tentatively assign this specimen to C. fochi, extending as such the known distribution of this species ca. 200 km to the southeast. Similarly, haplotypes from the candidate species identified by Mapelli et al. (2017) as “Arenales” form a clade with those of the nearby candidate species “Tupungato” identified by Parada et al. (2011); this clade (i.e., “the Arenales-Tupungato lineage”) is relatively homogenous (average percentage of genetic distance among the four included haplotypes: 1.00) and sister to the clade containing the haplotypes of C. fochi. Average genetic divergence between the “Arenales-Tupungato lineage” and that containing haplotypes of C. fochi is 1.86 %. Additional studies, including the assessment of morphological evidence, are needed to evaluate the status of these populations allied to C. fochi (i.e., Córdoba and in particular of the “Arenales-Tupungato lineage”).

In accordance with previous contributions, our analysis depicts that there are other lineages within the C. mendocinus species group that may represent distinct species; in some cases, no names appear to be available for them. Along with the above mentioned case of the “Arenales-Tupungato lineage”, there is the “Quijadas lineage”, from San Luis province, first identified by Mapelli et al. (2017). In any case, their distinction as different species needs to be further tested with other sources of evidence. Unfortunately, no vouchers associated with all these sequences are available, as some sequences were gathered from biopsies from animals later released. Finally, C. famosus, whose mitochondrial variation was recently described as arranged into two allopatric clades (“Velazco” and “Famatina” clades, sensu Tammone et al. 2022a), a result corroborated and expanded here, also needs to be further evaluated. According to our results, some samples from Antofagasta de la Sierra (Catamarca), first reported by Lacey et al. (2022) as Ctenomys sp., also belong to C. famosus (as part of the “Famatina clade” of Tammone et al. 2022a), enlarging to the north the distribution of this species ca. 260 km.

Of particular interest is the novel finding of a clade formed by the sequence of one specimen from Auca Mahuida, eastern Neuquén province (referred as C. sp. 4 by Tammone et al. 2021) and haplotypes of specimens (labeled by Carnovale et al. 2021 as C. azarae, which is now regarded as a synonym of C. mendocinus) from two localities, General Acha and Reserva Provincial Parque Luro, in La Pampa province (as stated above, we refer to this clade as to the “Neuquén-La Pampa lineage”). This is remarkable because the Pampean localities are in the distributional area of C. mendocinus (see D’Elía et al. 2021) and at both localities where collected other specimens whose sequences, gathered by Carnovale et al. (2021), form part of the clade C. mendocinus sensu stricto Remarkably, the clades corresponding to the Neuquén-La Pampa lineage and C. mendocinus sensu stricto are not sister to each other, as C. mendocinus sensu stricto appears sister to C. flamarioni; this suggests that the mitochondrial lineage referred to as the Neuquén-La Pampa lineage appears to be of species level. The possibility that two species of Ctenomys (i.e., C. mendocinus and the Neuquén-La Pampa lineage) occurring at General Acha and Reserva Provincial Parque Luro cannot be ruled out. Having said that, we note that no case of strict sympatry involving two or more species of Ctenomys is known, although at some areas, distinct species (e.g., C. australis and C. talarum; C. flamarioni and C. minutus) are distributed next to each other (see details in Bidau 2015). However, we note that a single coordinate was given in Carnovale et al. (2021), for each of these localities, meaning that if C. mendocinus and the Neuquén-La Pampa lineage are in fact distinct species, they occur in sympatry. Another possibility is that C. mendocinus and the Neuquén-La Pampa lineage represent a single species (i.e., C. mendocinus) that is paraphyletic with respect to C. flamarioni at the mitochondrial genome. This scenario is not unexpected, as several cases of non-monophyletic species at the mitochondrial genome are known (i.e., Rengifo et al. 2023); this is particularly true for species that are widespread and presumably have large effective population sizes. Unfortunately, no voucher specimens were secured for the samples from General Acha and Reserva Provincial Parque Luro, as DNA was extracted from tail tips of specimens that were later released (Carnovale et al. 2021: 3); as such, the phenotype of the specimens representative of these two mitochondrial lineages cannot be assessed in order to clarify if the Neuquén-La Pampa lineage represents a distinct species than C. mendocinus sensu stricto. This situation should be taken as a strong call of attention on the need to collect complete specimens and preserve them in biological collections, especially in groups, such as Ctenomys, whose alpha taxonomy is far from being well understood and stable.

Another fact of much interest is that three analyzed sequences (AF370697, MZ333061, MZ333062) labeled in GenBank as C. australis, fall within the clade of C. mendocinus. C. australis is a species with a geographic distribution along the southern Atlantic coast of Buenos Aires province and that is easy to distinguish morphologically from other nearby species (i.e., C. talarum) and those of the C. mendocinus species group (see details in Bidau 2015). As such, we maintain that C. australis represents a distinct lineage at the species level. Unfortunately, as in the case mentioned above, no voucher specimens are associated with these three sequences referred to as C. australis. As such, we cannot check the phenotype of these individuals to evaluate if they correspond to that of C. australis or other species (we mention that the only other species of Ctenomys known in the area where these specimens were collected, around the city of Necochea, is C. talarum, a species that does not belong to the C. mendocinus species group and is morphologically distinct from C. australis). Therefore, our results may reflect a case of incongruence between the gene and the species trees (see review in D’Elía et al. 2019), likely caused by retention of an ancestral polymorphism or introgression (in this later case of mtDNA of C. mendocinus into a genomic background of C. australis). More data, which should be gathered from vouchered specimens, are needed to clarify this scenario.

Recent advances in the taxonomy of the genus Ctenomys have greatly benefited from the use of biological collections; not only in the traditional ways (i.e, through the inspection of the phenotype of large specimen series) but also from the extraction of DNA from the skins of individuals collected decades ago (e.g., Teta and D’Elía 2020; Teta et al. 2022; this study). This last point highlights again the value of the specimens housed in biological collections, which can be studied through new methodologies in ways that were unsuspected at the time of their capture (e.g., Gardner et al. 2021). This reason invites us to continue collecting specimens in the field, both to fill geographic and temporal sampling gaps, which along current used approaches, would allow implementing data gathering and analyses not yet envisioned.

 Acknowledgements

We thank R. Lobo Allende, G. Zaia, E. A. Olivera, A. Y. Diaz Casas, and A. Castro for their assistance during fieldwork in La Rioja. O. Varela helped us with the environmental description of the El Peñón area. We are grateful to the curators and staff of the following collections: S. Bogan (CFA), R. Ojeda and B. Bender (CMI), S. Lucero (MACN), M. Diaz and Erick Gomez (CML), and F. Mondaca (UACH). F. Mapelli shared with us valuable information on Ctenomys. Scott Gardner and an anonymous reviewer made valuable comments that improved this study. Financial support was partially provided by the Universidad Nacional de Chilecito (Proyecto FICyT 2019 directed by Dra. R. Lobo Allende) and by FONDECYT grant 1221115 (GD).

 References AbreuEFJungDMHChristoffAUValiatiVHJansaSAPercequilloAR (2021) Systematics of Brucepattersonius Hershkovitz, 1998 (Rodentia, Sigmodontinae): Molecular species delimitation and morphological analyses suggest an overestimation in species diversity.Systematics and Biodiversity16: 544–570. https://doi.org/10.1080/14772000.2021.1890270 BidauCJ (2015) Family Ctenomyidae Lesson, 1842. In: PattonJLPardiñasUFJD’ElíaG (Eds) Mammals of South America, Volume 2: Rodents.University of Chicago Press, Chicago, IL, 818–877. BidauCJLessaEPOjedaRA (2012) Familia Ctenomyidae. In: OjedaRAChilloVDíaz IsenrathG (Eds) Libro Rojo.Mamíferos amenazados de La Argentina. Sociedad Argentina para el Estudio de los Mamíferos, Mendoza, 177–187. BorghiCEGiannoniSM (2007) Mamíferos. In: Martínez-CarreteroE (Ed.) Diversidad Biológica y Cultural de los Altos Andes Centrales de Argentina.Línea de Base de la Reserva de Biosfera San Guillermo, San Juan. Universidad Nacional de San Juan, San Juan, 155–164. BrookFTomascoIHGonzálezBMartinGM (2022) A new species of Ctenomys (Rodentia: Ctenomyidae) from Patagonia related to C. sociabilis.Journal of Mammalian Evolution29: 237–258. https://doi.org/10.1007/s10914-021-09570-9 CadenillasRD’ElíaG (2021) Taxonomic revision of the populations assigned to Octodon degus (Hystricomorpha: Octodontidae): With the designation of a neotype for Sciurus degus G. I. Molina, 1782 and the description of a new subspecies.Zoologischer Anzeiger292: 14–28. https://doi.org/10.1016/j.jcz.2021.02.008 CaraballoDARossiMS (2017) Integrative lineage delimitation in rodents of the Ctenomys Corrientes group.Mammalia82: 35–47. https://doi.org/10.1515/mammalia-2016-0162 CaraballoDALópezSLBotero-CañolaSGardnerSL (2023) Filling the gap in distribution ranges and conservation status in Ctenomys (Rodentia: Ctenomyidae). Journal of Mammalogy https://doi.org/10.1093/jmammal/gyac099 CarnovaleCSFernándezGPMerinoMLMoraMS (2021) Redefining the distributional boundaries and phylogenetic relationships for ctenomids from central Argentina. Frontiers in Genetics 12: 698134. http://doi.org/10.3389/fgene.2021.698134 ContrerasJRde ContrerasAN (1984) Craneología y craneometría del género Ctenomys. II: Craneometría.Historia Natural4: 245–248. CracraftJ (1983) Species concepts and speciation analysis. In: JohnstonRF (Ed.) Current Ornithology, Vol 1.Plenum, New York, NY, 159–187. DarribaDTaboadaGLDoalloRPosadaD (2012) jModelTest 2: More models, new heuristics and parallel computing. Nature Methods 9: 772. https://doi.org/10.1038/nmeth.2109 da SilvaMMPattonJL (1993) Amazonian phylogeography: mtDNA sequence variation in arboreal echimyid rodents (Caviomorpha).Molecular Phylogenetics and Evolution2: 243–255. https://doi.org/10.1006/mpev.1993.1023 D’ElíaGLessaEPCookJA (1999) Molecular phylogeny of tuco-tucos, genus Ctenomys (Rodentia: Octodontidae): Evaluation of the mendocinus species group and the evolution of asymmetric sperm.Journal of Mammalian Evolution6: 19–38. https://doi.org/10.1023/A:1020586229342 D’ElíaGFabrePHLessaEP (2019) Rodent systematics in an age of discovery: Recent advances and prospects.Journal of Mammalogy100: 852–871. https://doi.org/10.1093/jmammal/gyy179 D’ElíaGTetaPLessaEP (2021) A short overview of the Systematics of Ctenomys: species limits and phylogenetic relationships. In: FreitasTROGonçalvezGLMaestriR (Eds) Tuco-tucos.An Evolutionary Approach to the Diversity of a Neotropical Rodent. Springer, Cham, 17–41. http://doi.org/10.1007/978-3-030-61679-3 de QueirozK (1998) The General Lineage Concept of species, species criteria, and the process of speciation. In: HowardDJBerlocherSH (Eds) Endless Forms: Species and Speciation.Oxford University Press, New York, NY, 57–75. de QueirozK (2007) Species concepts and species delimitation.Systematic Biology56: 879–886. https://doi.org/10.1080/10635150701701083 De SantiNAVerziDHOlivaresAIPiñeroPMorganCCMedinaMERiveroDETonniEP (2020) A new peculiar species of the subterranean rodent Ctenomys (Rodentia, Ctenomyidae) from the Holocene of central Argentina. Journal of South American Earth Sciences 100: 102499. https://doi.org/10.1016/j.jsames.2020.102499 De SantiNAVerziDHOlivaresAIPiñeroPÁlvarezAMorganCC (2021) A new Pleistocene Ctenomys and divergence dating of the hyperdiverse South American rodent family Ctenomyidae.Journal of Systematic Palaeontology19: 377–392. https://doi.org/10.1080/14772019.2021.1910583 FelsensteinJ (1981) Evolutionary trees from DNA sequences: A maximum likelihood approach.Journal of Molecular Evolution17: 368–376. https://doi.org/10.1007/BF01734359 FornelRCordeiro-EstrelaPFreitasTRO (2018) Skull shape and size variation within and between mendocinus and torquatus groups in the genus Ctenomys (Rodentia: Ctenomyidae) in chromosomal polymorphism context.Genetics and Molecular Biology41: 263–272.https://doi.org/10.1590/1678-4685-GMB-2017-0074 FreitasTROFernandesFAFornelRRorattoPA (2012) An endemic new species of tuco-tuco, genus Ctenomys (Rodentia: Ctenomyidae), with a restricted geographic distribution in southern Brazil.Journal of Mammalogy93: 1355–1367. https://doi.org/10.1644/12-MAMM-A-007.1 GardnerSLSalazar BravoJCookJA (2014) New Species of Ctenomys Blainville 1826 (Rodentia: Ctenomyidae) from the lowlands and central valleys of Bolivia.Special Publications, The Museum of Texas Tech University62: 1–34. GardnerSLBotero-CañolaSAliaga-RosselEDursahinhanATSalazar-BravoJ (2021) Conservation status and natural history of Ctenomys, tuco-tucos in Bolivia.Therya12: 15–36. https://doi.org/10.12933/therya-21-1035 GuayasaminJMAlejandro ArteagaAHutterCR (2018) A new (singleton) rainfrog of the Pristimantis myersi Group (Amphibia: Craugastoridae) from the northern Andes of Ecuador.Zootaxa4527: 323–334. https://doi.org/10.11646/zootaxa.4527.3.2 HaeneEMontanezACarrizoABodratiGBonoJKraussGMéridaERodríguezRJonesJPérezA (2001) Primer inventario de los animales vertebrados del Parque Nacional San Guillermo (Provincia de San Juan, Republica Argentina).Boletín de la Sociedad Biológica de Concepción, Chile72: 59–67. HammerOHarperDATRyanPD (2001) PAST: Paleontological statistic software package for education and data analysis.Paleontologia Eletronica4: 1–9. HoangDTChernomorOvon HaeselerAMinhBQVinhLS (2018) UFBoot2: Improving the ultrafast bootstrap approximation.Molecular Biology and Evolution35: 518–522. https://doi.org/10.1093/molbev/msx281 KeltDAGallardoMH (1994) A new species of tuco-tuco, genus Ctenomys (Rodentia: Ctenomyidae) from Patagonian Chile.Journal of Mammalogy75: 338–348. https://doi.org/10.2307/1382552 KöhlerJPadialJM (2016) Description and phylogenetic position of a new (singleton) species of Oreobates Jiménez de la Espada, 1872 (Anura: Craugastoridae) from the Yungas of Cochabamba, Bolivia.Annals of Carnegie Museum84: 23–38. https://doi.org/10.2992/007.084.0104 LaceyEAAmayaJPIrianCGCarrizoPGO’BrienSLOjedaAA (2022) Variable social organization among tuco-tucos (genus Ctenomys) in the opimus clade.Journal of Mammalogy103: 979–992. https://doi.org/10.1093/jmammal/gyac015 LeipnitzLTFornelRRibasLEJKubiakBBGalianoDFreitasTRO (2020) Lineages of tuco-tucos (Ctenomyidae: Rodentia) from midwest and northern Brazil: Late irradiations of subterranean rodents towards the Amazon forest.Journal of Mammalian Evolution27: 161–176. https://doi.org/10.1007/s10914-018-9450-0 Londoño-GaviriaMTetaPRíosSDPattersonBD (2019) Redescription and phylogenetic position of Ctenomys dorsalis Thomas 1900, an enigmatic tuco tuco (Rodentia, Ctenomyidae) from the Paraguayan Chaco.Mammalia83: 227–236. https://doi.org/10.1515/mammalia-2018-0049 MapelliFJMoraMSLanciaJPGómez FernándezMJMirolPMKittleinMJ (2017) Evolution and phylogenetic relationships in subterranean rodents of the Ctenomys mendocinus species complex: Effects of Late Quaternary landscape changes of Central Argentina.Mammalian Biology87: 130–142. https://doi.org/10.1016/j.mambio.2017.08.002 MapelliFJTetaPContrerasFPereyraDPriottoJCodaJ (2022) Looking under stones: A new Ctenomys species from the rocky foothills of the Sierras Grandes of central Argentina. Journal of Mammalian Evolution. https://doi.org/10.1007/s10914-022-09634-4 MassariniAIBarrosMAOrtellsMOReigOA (1991) Chromosomal polymorphism and small karyotypic differentiation in a group of Ctenomys species from Central Argentina (Rodentia: Octodontidae).Genetica83: 131–144. https://doi.org/10.1007/BF00058530 MascherettiSMirolPGimenezMBidauCContrerasJRSearleJ (2000) Phylogenetics of the speciose and chromosomally variable genus Ctenomys (Ctenomyidae, Octodontoidea), based on mitochondrial cytochrome b sequences.Biological Journal of the Linnean Society70: 361–376. https://doi.org/10.1006/bijl.1999.0394 NguyenL-TSchmidtHAvon HaeselerAQuang MinhBQ (2015) IQ-TREE: A fast and effective stochastic algorithm for estimating maximum-likelihood phylogenies. Molecular Biology and Evolution 32: 268274. https://doi.org/10.1093/molbev/msu300 OlsonDMDinersteinEWikramanayakeEDBurgessNDPowellGVNUnderwoodECD'AmicoJAItouaIStrandHEMorrisonJCLoucksCJAllnuttTFRickettsTHKuraYLamoreuxJFWettengelWWHedaoPKassemKR (2001) Terrestrial ecoregions of the world: A new map of life on earth: A new global map of terrestrial ecoregions provides an innovative tool for conserving biodiversity. BioScience 51: 933–938. https://doi.org/10.1641/0006-3568(2001)051[0933:TEOTWA]2.0.CO;2 ParadaAD’ElíaGBidauCJLessaEP (2011) Species groups and the evolutionary diversification of tuco-tucos, genus Ctenomys (Rodentia: Ctenomyidae).Journal of Mammalogy92: 671–682. https://doi.org/10.1644/10-MAMM-A-121.1 ParadaAOjedaAATabeniSD’ElíaG (2012) The population of Ctenomys from the Ñacuñán Biosphere Reserve (Mendoza, Argentina) belongs to Ctenomys mendocinus Philippi, 1869 (Rodentia: Ctenomyidae): Molecular and karyotypic evidence.Zootaxa3402: 61–68. https://doi.org/10.11646/zootaxa.3402.1.5 PradhanNNorrisRWDecherJPeterhansJKGrayCRBauerGCarletonMDKilpatrickCW (2021) Phylogenetic relationships and biogeography of the Hybomys division (Muridae: Murinae: Arvicanthini), rodents endemic to Africa’s rainforests.Journal of Vertebrate Biology70: 1–26. https://doi.org/10.25225/jvb.21034 RannalaBYangZ (1996) Probability distribution of molecular evolutionary trees: A new method of phylogenetic inference.Journal of Molecular Evolution43: 304–311. https://doi.org/10.1007/BF02338839 RengifoEMD’ElíaGGarcíaGCharpentierECornejoFM (2023) A new species of titi monkey, genus Cheracebus (Primates: Pitheciidae), from Peruvian Amazonia.Mammal Study48: 3–18. https://doi.org/10.3106/ms2022-0019 RidgwayR (1912) Color standards and color nomenclature. Published by the author, Washington, DC. RonquistFHuelsenbeckJP (2003) MrBayes 3: Bayesian phylogenetic inference under mixed models.Bioinformatics19: 1572–1574. https://doi.org/10.1093/bioinformatics/btg180 RosiMIScolaroJAVidelaF (1992) Distribución y relaciones sistemáticas entre poblaciones del género Ctenomys (Rodentia: Ctenomyidae) de la provincia de Mendoza.Miscellánia Zoológica16: 207–222. RowseyDMDuyaMRMIbañezJCJansaSARickartEAHeaneyLR (2022) A new genus and species of shrew-like mouse (Rodentia: Muridae) from a new center of endemism in eastern Mindanao, Philippines.Journal of Mammalogy103: 1259–1277. https://doi.org/10.1093/jmammal/gyac057 SánchezRHTomascoIHDíazMMBarquezRM (2019) Contribution to the knowledge of the rare “Famatina tuco-tuco”, Ctenomys famosus Thomas 1920 (Rodentia: Ctenomyidae).Mammalia83: 11–22. https://doi.org/10.1515/mammalia-2017-0131 SAYDS-SAREM (2019) Categorización 2019 de los mamíferos de Argentina según su riesgo de extinción. Lista Roja de los mamíferos de Argentina. http://cma.sarem.org.ar SmithMFKeltDAPattonJL (2001) Testing models of diversification in mice in the Abrothrix olivaceus/xanthorhinus complex in Chile and Argentina.Molecular Ecology10: 397–405. https://doi.org/10.1046/j.1365-294x.2001.01183.x StraussRE (2010) Discriminating groups of organisms. In: AshrafE (Ed.) Morphometrics for nonmorphometricians.Lecture Notes in Earth Sciences 124, Springer, Berlin, 73–91. TammoneMNLaceyEAVoglinoDCuéllar-SotoEPardiñasUFJ (2021) Disentangling the complex alpha taxonomy of Andean populations of Ctenomys (Rodentia: Ctenomyidae) from northern Patagonia: The need for extensive sampling in heterogeneous landscapes.Journal of Mammalogy102: 1405–1425. https://doi.org/10.1093/jmammal/gyab089 TammoneMNFariñas TorresTOjedaAAChemisquyMA (2022a) Disentangling the taxonomic status of Ctenomys (Rodentia: Ctenomyidae) populations inhabiting northern areas of La Rioja Province, Argentina.Mammalia86: 527–538. https://doi.org/10.1515/mammalia-2021-0169 TammoneMNLaceyEAPardiñasUFJ (2022b) A century of stasis: Taxonomy of Ctenomys (Rodentia: Hystricomorpha) populations in northeastern Patagonia limits, Argentina.Zoologischer Anzeiger298: 136–147. https://doi.org/10.1016/j.jcz.2022.04.002 TamuraKStecherGPetersonDFilipskiAKumarS (2013) MEGA6: Molecular evolutionary genetics analysis version 6.0.Molecular Biology and Evolution30: 2725–2729. https://doi.org/10.1093/molbev/mst197 TetaPD’ElíaG (2020) Uncovering the species diversity of subterranean rodents at the end of the World: Three new species of Patagonian tuco-tucos (Rodentia, Hystricomorpha, Ctenomys). PeerJ 8: e9259. https://doi.org/10.7717/peerj.925 TetaPD’ElíaGOpazoJ (2020) Integrative taxonomy of the southernmost tucu-tucus in the world: Differentiation of the nominal forms associated with Ctenomys magellanicus Bennett, 1836 (Rodentia, Hystricomorpha, Ctenomyidae).Mammalian Biology100: 125–139. https://doi.org/10.1007/s42991-020-00015-z TetaPJayatJPOrtizPE (2022) Una nueva especie del género Microcavia (Rodentia, Caviidae) para las tierras altas del noroeste de Argentina.Therya13: 103–114. https://doi.org/10.12933/therya-22-1217 TetaPQuiroga-CarmonaMD’ElíaG (2021) Imperiled or not? Characterizing the non-charismatic and Data Deficient South American rodents. In: DellaSalaDAGoldsteinMI (Eds) Imperiled: The Encyclopedia of Conservation.Elsevier, Amsterdam, 519–528. ThomasO (1920a) On small mammals from the Famatina Chain, north-western Rioja. Annals and Magazine of Natural History, Series 9, 6: 417–422. ThomasO (1920b) On mammals from near Tinogasta, Catamarca, collected by Sr. Budin. Annals and Magazine of Natural History, Series 9, 6: 116–120. ThomasO (1921) On mammals from the Province of San Juan, western Argentina. Annals and Magazine of Natural History, Series 9, 8: 214–221. TrinoupoulusJNguyenLTvon HaeselerAMinhBQ (2016) W-IQ-TREE: A fast online phylogenetic tool for maximum likelihood analysis.Nucleic Acids Research44: 232–235. https://doi.org/10.1093/nar/gkw256 ZhangTLeiMLZhouHChenZZShiP (2022) Phylogenetic relationships of the zokor genus Eospalax (Mammalia, Rodentia, Spalacidae) inferred from whole-genome analyses, with description of a new species endemic to Hengduan Mountains.Zoological Research43: 331–342. https://doi.org/10.24272/j.issn.2095-8137.2022.045 Supplementary materials 8F111AED-D6D7-5B7F-96F3-64B07F2D6891

File 1

: .docx

: List of cytochrome b gene sequences of specimens of the Ctenomys mendocinus species group included in the genetic based analyses. For each sequence, details of species/lineage (see text), Genbank accession numbers and geographic provenance are given. Sequences gathered here are indicated with an #. For these sequences catalog numbers are also provided (see collection acronyms in the main text). Sequences with a * correspond to samples referred in Genbank as of C. australis (see the discussion in the main text). Sequences identified with a ^ were gathered from paratypes of C. validus (see discussion in the main text). Species/lineage assignment follows the taxonomy discussed in the text.

 https://binary.pensoft.net/file/850088 This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Teta P, Jayat JP, Alvarado-Larios R, Ojeda AA, Cuello P, D’Elía G (2023) B8E682A3-7713-57B0-AA0C-5C377CE9866E

File 2

: .xlsx

: Individual measurements for specimens of Ctenomys used in the morphological analysis. For collection acronyms and measuremnt abreviattions see the section of “Materials and methods”.

 https://binary.pensoft.net/file/850089 This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Teta P, Jayat JP, Alvarado-Larios R, Ojeda AA, Cuello P, D’Elía G (2023) 19F1C8AE-33DF-5E7E-AB4B-AC017429A80D

File 3

: .xlsx

: External measurements (in mm) of the paratypes of Ctenomys eileenae n. sp. See the text for abreviattions.

 https://binary.pensoft.net/file/850090 This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Teta P, Jayat JP, Alvarado-Larios R, Ojeda AA, Cuello P, D’Elía G (2023) 34CB62EF-55CA-5CB9-BDFB-0D96658F7C47

File 4

: .docx

: Supplementary figures.

 https://binary.pensoft.net/file/850091 This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Teta P, Jayat JP, Alvarado-Larios R, Ojeda AA, Cuello P, D’Elía G (2023)