Ctenomys verzi, Teta & Jayat & Alvarado-Larios & Ojeda & Cuello & D’Elía, 2023

Teta, Pablo, Jayat, J. Pablo, Alvarado-Larios, Raquel, Ojeda, Agustina A., Cuello, Pablo & D'Elia, Guillermo, 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, pp. 451-474 : 451

publication ID	https://dx.doi.org/10.3897/vz.73.e101065
publication LSID	lsid:zoobank.org:pub:BD96329D-A6E3-46C8-94A9-50C1B198BB89
persistent identifier	https://treatment.plazi.org/id/935F6E2F-0B11-40E5-98A4-ECB57F73E160
taxon LSID	lsid:zoobank.org:act:935F6E2F-0B11-40E5-98A4-ECB57F73E160
treatment provided by	Vertebrate Zoology by Pensoft
scientific name	Ctenomys verzi
status	sp. nov.

Treatment

Ctenomys verzi sp. nov.

Figs 6 View Figure 6 , 9 View Figure 9 , 10 View Figure 10 , 11 View Figure 11 , 12 View Figure 12

Ctenomys sp. Las Leñas - Mapelli et al. (2017: 133)

Ctenomys sp. 3 - Tammone et al. (2021: 1407)

Ctenomys Verzi’s tuco-tuco

Ctenomys 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 View Figure 6 , 9 View Figure 9 - 12 View Figure 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 View Figure 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 View Figure 10 ).

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 View Figure 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 View Figure 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 View Figure 11 ).

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 View Figure 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 View Figure 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 View Figure 2 , locality 12), at the Andes of southwestern Mendoza in west-central Argentina (Fig. 2 View Figure 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 verzi sp. 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 View Figure 9 , 12 View Figure 12 ). Additionally, the tympanic bullae are not visible from above in Ctenomys verzi sp. nov., while they visible in dorsal view in both C. johannis and C. mendocinus (Fig. 12 View Figure 12 ).

Ctenomys verzi sp. nov. can be differentiated from Ctenomys eileenae sp. 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 verzi sp. nov. lacks postorbital processes, while these structures are moderately to well developed in Ctenomys eileenae sp. nov.

Ctenomys verzi sp. 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 View Figure 9 ). In addition, the interpremaxillary foramen is large and closely placed to the incisive foramina in Ctenomys verzi sp. nov. and large but well separated from the incisive foramina in the C. emilianus (Fig. 6 View Figure 6 ).

Ctenomys verzi sp. 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 verzi sp. nov. and large but well separated from the incisive foramina in C. maulinus (Fig. 9 View Figure 9 ).

Ctenomys verzi sp. 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 View Figure 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 View Figure 9 ).

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