Ctenomys eileenae, 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/F1355C16-11F3-40C9-8E40-3C90EEE2C2F9
taxon LSID	lsid:zoobank.org:act:F1355C16-11F3-40C9-8E40-3C90EEE2C2F9
treatment provided by	Vertebrate Zoology by Pensoft
scientific name	Ctenomys eileenae
status	sp. nov.

Treatment

Ctenomys eileenae sp. nov.

Figs 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 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)

Ctenomys Eileen’s tuco-tuco

Ctenomys 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 View Figure 4 - 6 View Figure 6 ). An 801 base-pair sequence of the cyt b gene has been deposited in GenBank with accession number OQ305623.

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 View Figure 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 View Figure 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 View Figure 2 , locality 2]); Parque Nacional San Guillermo, Cerro Imán (MACN-Ma 18817, MACN-Ma 18819, MACN-Ma 18828 [Fig. 2 View Figure 2 , locality 3]); Parque Nacional San Guillermo, Los Caserones (MACN-Ma 18816, MACN-Ma 18818 [Fig. 2 View Figure 2 , locality 4]); Parque Nacional San Guillermo, Mina La Brea (MACN-Ma 18824; [Fig. 2 View Figure 2 , locality 5]); Parque Nacional San Guillermo, Puesto Agua del Godo (MACN-Ma 18813, MACN-Ma 18814, MACN-Ma 18815 [Fig. 2 View Figure 2 , locality 6]); Parque Nacional San Guillermo, Refugio del Macho Muerto (MACN-Ma 18825; [Fig. 2 View Figure 2 , locality 7]); Parque Nacional San Guillermo, Rincón del Río (MACN-Ma 18826, MACN-Ma 18827 [Fig. 2 View Figure 2 , locality 8]); Parque Nacional San Guillermo, Vega Agua del Godo (CML 430, CML 1916 [Fig. 2 View Figure 2 , locality 9]); Parque Nacional San Guillermo, Vega del Infiernillo (MACN-Ma 18822 [Fig. 2 View Figure 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 View Figure 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 View Figure 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 View Figure 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 View Figure 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 View Figure 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 View Figure 5 ).

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

Descriptive statistics for external and cranial measurements are provided on Table 2 View 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 View Figure 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 eileenae sp. 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 View Figure 6 - 8 View Figure 8 ). Furthermore, the postorbital processes in Ctenomys eileenae sp. nov. are moderately to well developed, while in C. bergi , C. fochi , C. johannis , C. mendocinus , and C. tulduco are absent to slightly expressed.

Ctenomys eileenae sp. 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 eileenae sp. nov. has moderately to well-developed postorbital processes, while in C. coludo and C. famosus this structure is mostly absent.

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

Ctenomys eileenae sp. 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 View Figure 7 ). In addition, Ctenomys eileenae sp. nov. has proportionally broader incisive foramina.

Ctenomys eileenae sp. 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 View Figure 7 and 8 View Figure 8 ).

Ctenomys eileenae sp. nov. can be differentiated from C. verzi sp. 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 eileenae sp. nov. has moderately to well-developed postorbital processes, while in C. verzi sp. 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 View 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 eileenae sp. nov. is distributed over an area of ca. 900 km2 in western La Rioja and northernmost San Juan provinces, west-central Argentina (Fig. 2 View Figure 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.