Cardiatherium calingastaense, Cerdeño & Pérez & Deschamps & Contreras, 2019

Cerdeño, Esperanza, Pérez, María E., Deschamps, Cecilia M. & Contreras, Víctor H., 2019, A new capybara from the late Miocene of San Juan Province, Argentina, and its phylogenetic implications, Acta Palaeontologica Polonica 64 (1), pp. 199-212 : 202-207

publication ID	https://doi.org/ 10.4202/app.00544.2018
publication LSID	lsid:zoobank.org:pub:2A1D2DDE-7100-4BC7-B0B1-8862CC1A064E
persistent identifier	https://treatment.plazi.org/id/343DF38E-F84D-43C7-9687-05C91FF26257
taxon LSID	lsid:zoobank.org:act:343DF38E-F84D-43C7-9687-05C91FF26257
treatment provided by	Felipe
scientific name	Cardiatherium calingastaense
status	sp. nov.

Treatment

Cardiatherium calingastaense sp. nov.

Figs. 3 View Fig , 4 View Fig .

2010 Cardiatherium sp. ; Contreras and Cerdeño 2010: 8 R.

ZooBank LSID: urn:lsid:zoobank.org:act:343DF38E-F84D-43C7-9687-05C91FF26257

Etymology: After the Calingasta Valley, where the locality of Puchuzum is located.

Holotype: INGEO-PV 87 , skull and mandible of an adult individual, together with associated fragments of vertebrae and long bones.

Type locality: Right side of the Candelaria Creek, Puchuzum area, Calingasta Valley, San Juan Province, central-west Argentina.

Type horizon: Mid stratigraphic section of Las Flores Formation, late Miocene.

Diagnosis.—Cavioid diagnosed by the following unique combination of characters (autapomorphies marked with an asterisk): euhypsodont cheek teeth; p4 with three prisms and P4 with two-lobed prisms as in other Hydrochoerinae ; p4 with hfe, h3e, hpi, h2i, and h3i as in Hydrochoeropsis , Phugatherium , Neochoerus , and Hydrochoerus ; h2i and h3i equally deep as in Cardiatherium paranense , Hydrochoeropsis dasseni , but differing from Hydrochoerus and Neochoerus in which h2i is shallower than h3i and its apex is behind the hfe; p4 with hse (h2e) as in C. patagonicum ; p4 lacks h5i and hsni, as in C. paranense ; hpi, hti, HFI, and hfe of m1/M1–m2/M2 not splitting the teeth, as in other Cardiatherium and differing from Hydrochoeropsis , Phugatherium , Neochoerus , and Hydrochoerus , in which those flexi/ids completely cross the tooth; *m3 with a conspicuous labial column in the posterior ramus of prIIa in contrast to other species; HPE and HSE very deep, the latter shorter than the former but deeper than in other species and oriented backwards; M3 with nine prisms; sagittal crest on the parietals, unlike Hydrochoeropsis , Phugatherium , Neochoerus , and Hydrochoerus , in which the area between both temporal fossae is plane, without forming the sagittal crest; bullae small in ventral view as in Neochoerus and Hydrochoerus ;

scars marking the origin of the masseter medialis muscle on the beginning of the anterior zygomatic arch (ventral face), with an anterior projection up to the level of the incisive foramen and the maxilla-premaxilla suture.

Description.—As it is reflected in the diagnosis of the new proposed taxon, the specimen INGEO-PV 87 ( Figs. 3 View Fig , 4 View Fig ) may be referred to the genus Cardiatherium , discarding its assignment to other genera of capybaras such as Phugatherium , Hydrochoeropsis or the modern lineages represented by Hydrochoerus and Neochoerus (see also Phylogenetic analysis and Discussion). Therefore, the following description is focused on the comparison of the studied material with the known species of Cardiatherium .

Skull: It is somewhat mediolaterally deformed and lacks the left zygomatic arch, the left parietal-occipital area, and the left M3 ( Fig. 3A View Fig 1, A 2 View Fig ).

In dorsal view ( Fig. 3A View Fig 1), the nasal is anterolaterally broken but the preserved portion indicates that this bone is long. The nasal is a little longer than the frontal in the new species as in C. paranense and the biggest capybaras Phugatherium , Hydrochoeropsis , Hydrochoerus ). Laterally, the nasal is in contact with the dorsal projection of the premaxilla and posteriorly with the frontal. The nasal is dorsally slightly convex, differing from the strongly bulging condition of C. paranense and from Hydrochoerus , in which the nasal is slightly bulky in the middle portion. The posterior border of the nasal is anteriorly slightly concave, differing from the strongly concave border of C. paranense . The nasal and frontal ( Fig. 3A View Fig 1) are proportionately narrower than in C. paranense , Phugatherium , and Hydrochoerus . The frontal and the anterior portion of the parietal are dorsally flat as in most Hydrochoerinae . The posterior portion of the parietal has a temporal fossa posterolaterally concave and the temporal lines join, although not completely fusing, in a short sagittal crest that diverges again posteriorly at the nuchal crest.

This condition contrasts with that of the largest capybaras, which present an interposed area between the temporal fossae (which are shallower than in C. calingastaense sp. nov.) instead of the sagittal crest. The postorbital apophyses are incomplete and would have been short.

In right lateral view, the ventral portion of the zygomatic arch is preserved and is similar to the condition of Hydrochoerus . The maxillary anterior root of the arch is dorso-ventrally flattened and narrows posteriorly, being dorso-ventrally elongated like the jugal, which is antero-posteriorly short. The squamosal forms the posterior portion of the arch and is posteriorly extended above the tympanic bulla. The external auditory meatus is above the level of the molar series. The angle formed by the anterior root of the zygomatic arch and the alveolar plane in Lateral view is <20°, similar to C. paranense , but different from C. aff. orientalis from the Cerro Azul Formation, in which it is 24–26° ( Vucetich et al. 2014b).

In ventral view ( Fig. 3A View Fig 2 View Fig ), the diastema is longer than the molariform series ( Table 1), like in C. paranense , C. patagonicum , H. dasseni , and P. novum . The scars for the insertion of the masseter superficialis muscle are anteriorly convergent as in the other species of Cardiatherium ; however, in INGEO-PV 87 there is an additional scar in this area. One is oval, transversely concave, placed between the root of the zygomatic arch and the P4, but extended anteriorly beyond this tooth, as observed in the other species of the genus; and the other one is another smooth surface at an obtuse angle with the first scar, which is directed to the sagittal plane, reaching the border of the incisive foramen, where the premaxilla-maxilla suture is located ( Fig. 3A View Fig 2 View Fig , A 3 View Fig ). The incisive foramen is ovoid and broad as in C. paranense whereas it is narrow in C. aff. orientalis ( Table 1). The base of P4 does not project laterally and therefore does not form the bulge observable in ventral view in C. paranense . The ratio between the distance from the base of the incisive foramen up to the middle point between both P4s and the upper tooth series length is close to the minimum values of Cardiatherium , but different from the large capybaras ( Phugatherium ) and the modern lineages ( Hydrochoerus – Neochoerus ), in which the tooth series is proportionally longer ( Table 1). The palate is rather shallow; from the level of M1 to that of the third prism of M3, there is a medium, narrow crest with a long and narrow palatal foramen at each side (M2–M3 level). The mesopterygoid fossa is narrow in outline, with a rounded anterior margin at the level of the posterior portion of the M3, as in C. paranense and C. patagonicum . The tooth rows are divergent, but with a smooth curvature with M3 aligned with P4–M2, as in C. paranense . In C. patagonicum and C. aff. orientalis , the M3 are nearly parallel. The basicranium is badly preserved, although part of the basisphenoid and the right tympanic bulla are preserved. The bulla is relatively small. The occipital face is incomplete and displaced; the right paraoccipital apophysis is distally incomplete, but it would have been relatively long ( Fig. 3A View Fig 1).

Mandible: The mandible preserves the symphysis, with the incisors, most of the left horizontal ramus, with p4–m3, and the anterior part of the right ramus ( Fig. 3B View Fig ). The right cheek teeth were recovered separately, but complete. The symphysis is narrow and procumbent, with a smooth median keel on the labial side; the posterior end of the symphysis does not reach the premolar level. The horizontal rami are well divergent; they are wide and vertically convex; ventrally, the area from the level below m1 to the base of the symphysis is flattened. The mental foramen is located anteriorly to p4 and at the dorso-ventral midpoint of the lateral surface of the dentary. The bottom of the i1 alveolus reaches internally the anterior half of the m2 and widens the lingual side of the ramus (clearly visible on the left side). The posterior border of the symphysis in C. calingastaense sp. nov. is below p4; according to Vucetich et al. (2005) and Deschamps et al. (2007), its position depends on the age of individuals, located anterior of p 4 in juveniles and below the midpoint of p 4 in larger (older) individuals. Main mandibular measurements are provided in Table 2.

Dentition: Both upper and lower incisors are narrow (I1, 8.1 mm; i1, 7.4 mm and 7.6 mm) and strongly curved, with bevelled occlusal surface and enamel only on the labial side ( Fig. 3B View Fig ).

Among upper cheek teeth ( Fig. 4A View Fig 1 –A 4 View Fig ; Table 3), P4, M1, and M2 are formed by two heart-shaped prisms, joined by a short isthmus. As in all species of Cardiatherium, HPE is deeper than HSE, unlike Phugatherium in which these flexi are almost similar in depth ( Fig. 5A–E View Fig ). In INGEO-PV 87, the HPE is very deep and curved backward, in such a way that in M2 it reaches the labial side and produces a deformation of this wall resulting in a strong step-shaped profile ( Figs. 4A View Fig 2 View Fig , A 3 View Fig , 5A View Fig ). The HSE is shorter than HPE, but is deeper than in the other species and oriented slightly backward ( Fig. 5A–C View Fig ); only the largest specimen of C. patagonicum has an HSE similar in depth to C. calingastaense sp. nov., but anteriorly

Symphysis length 51.5 Anterior transversal diameter of symphysis 23.6 Transversal diameter symphysis at foramen level 31.9 Anterior height of symphysis c. 23.4 Height symphysis at foramen level 24.0 Transversal diameter between p4s, anterior to alveolus 30.6 Height horizontal ramus ahead left p4 20.3 Maximum width anterior to lateral crest 67.1

concave. P4 has undulated walls of HPE. The HFI is so deep that it almost splits prI from prII. M3 has nine prisms; prI is bilobed with a deep HPE similar to those of the other upper cheek teeth; the other eight prisms are laminar with a shallow, open V-shaped labial fissure in prII to prVII whereas in prVIII there is a barely marked labial concavity; as usual in capybaras, prIX is transversally shorter with a convex posterior margin and no labial fissure ( Figs. 4A 4 View Fig , 5A View Fig ).

Among lower cheek teeth ( Figs. 4A View Fig 5 –A View Fig 9, 6A; Table 4), p4 has a deep h3e, bifurcated at the end, and anteriorly directed. C. calingastaense sp. nov. lacks h4i and h5i as C. paranense ( Fig. 6C View Fig ), whereas h5i is extended up to 25% of the occlusal surface in C. patagonicum ( Fig. 6B View Fig ), C. orientalis ( Fig. 6D View Fig ) and C. chasicoense ( Fig. 6E View Fig ). C. calingastaense sp. nov. and C. aff. orientalis have no supernumerary internal flexid (hsni) typical of C. orientalis and C. patagonicum ( Fig. 6B, D View Fig ). The hfe is also deep, wide and transversely directed whereas in other species it is oblique. Lingually, the hpi is transversely directed and very deep, reaching almost the labial side, producing a deformation on this margin; at the same time, the third external flexid (h2e) is markedly concave ( Figs. 4A View Fig 8, A 9, 6A) whereas in C. patagonicum (also with very deep hpi) the h2e is only incipient ( Fig. 6B View Fig ). The h2i and h3i are long and also bifurcated at the end, and both delimit a conspicuous internal column (c3). In C. patagonicum , h2i is much shallower than h3i; in C. paranense ( Fig. 6C View Fig ) and C. chasicoense ( Fig. 6E View Fig ), these flexids are shallower and similar in depth, those of the latter being the shallowest.

The m1–m2 are similar in morphology ( Figs. 4A View Fig 6, 6A View Fig ). The hsi penetrates less than 50% of the width of prI as in the other species of Cardiatherium , whereas hti is deep (crossing the prism but not splitting as in C. patagonicum ; Fig. 6B View Fig ) and Phugatherium ) and bifurcated at the end, producing a deformation of the labial margin at this point. The hse is deep and wide. The m3 is the longest molar of the series, and flexids are not bifurcated. This molar has a conspicuous labial column in the posterior ramus of prIIa, delimited by two accessory fissures between hse and hfe ( Figs. 4A View Fig 7 View Fig , 6A View Fig ).

The previous comparative description has been focused on the best-known species, but some comparison can also be provided for two other poorly known taxa. In C. isseli (holotype and only specimen MACN 6354; middle Miocene, Río Negro Province; Rovereto 1914), the p4 is quite similar, but the m3 differs because the anterior margin of prI is straight and the hsi is very deep. In C. talicei (holotype SPV-FHC-10-VIII-63-1; Pliocene, San Gregorio, Uruguay; Francis and Mones 1965a; Mones 1991, who adds two other specimens), the flexids are anteroposteriorly wider; the p4 has deeper h4i and no h2e; h2i and h3i are shallower, especially the former; and the m3 shows a deep hsi, more anteriorly directed than in C. calingastaense sp. nov., which is reflected in a longer and more triangular first prism.

Stratigraphic and geographic range.—Late Miocene, middle section of the Las Flores Formation. Right side of the Candelaria Creek, Puchuzum area, Calingasta Valley, San Juan Province, central-west Argentina..