Neocavia sp.

Madozzo-Jaén, M. Carolina, Pérez, M. Encarnación, Montalvo, Claudia I. & Tomassini, Rodrigo L., 2018, Systematic review of Neocavia from the Neogene of Argentina: Phylogenetic and evolutionary implications, Acta Palaeontologica Polonica 63 (2), pp. 241-260 : 253

Neocavia sp.

Figs. 4B , 5J.

Material.— MD-FM-17-01 , fragment of left mandible with p4–m1, and broken m2 ( Figs. 4B , 5J) from the lower levels of the Monte Hermoso Formation , early Pliocene , Montehermosan Stage / Age (see Tomassini et al. 2013), of Farola Monte Hermoso, Buenos Aires Province, Argentina ( Fig. 1C ) .

Description.— Dentary: This specimen is a little more robust than other specimens of the genus ( Table 3). In labial view ( Fig. 4B 1 ), only the anterior part of the nMpi has been preserved, which is located between m1 and m2 ( Fig. 4B 3 ) as in N. pampeana sp. nov. and N. lozanoi ; the condition of “ N. depressidens ” is unknown. In lingual view ( Fig. 4B 2 ), the lower incisor extends posteriorly up to the level of the anterior lobe of m1, as in N. lozanoi and N. pampeana sp. nov. In ventral view, the alveolar protuberance of m1 is well-developed.

Lower teeth: The molariforms (Fig. 5J) are double-heart shaped, and the hypoflexid is funnel-shaped. The anteroposterior length of the molariforms is larger than in other species of Neocavia and both lobes of m1 are similar in anteroposterior length, as in N. lozanoi . Neocavia sp. differs from N. pampeana sp. nov. because the anteroposterior length of the anterior lobe is greater than the posterior lobe ( Fig. 6B, C;

Dp4

Table 3). The h.p.i. is narrower than in N. pampeana sp. nov. and N. lozanoi , and differs from “ N. depressidens ” because it is very shallow (Fig. 5J). The anterior lobe of p4 has an incipient anterior projection, as in N. pampeana sp. nov.; on the contrary, in N. lozanoi , when present, the anterior projection is well-developed, whereas it is absent in “ N. depressidens ”.

Remarks.—Here we opted for retaining an open taxonomy for Neocavia sp. because there is only one specimen with a combination of few characters; for this reason is not possible to check if the larger size and the morphological differences (i.e., narrower h.p.i., both lobes of m1 similar in anteroposterior length, and incipient anterior projection of p4) correspond to intra or interspecific variability. In addition, the comparison with “ N. depressidens ”, also recovered in the Monte Hermoso Formation, is inaccurate because the holotype (and the only specimen known) is missing (see above).

Figures

Fig. 4. Mandibles of the caviid rodent Neocavia from the Neogene of Argentina. A. Neocavia lozanoi Kraglievich, 1932 from the “Araucanense”, late Miocene–early Pliocene, Andalhuala locality, Santa María Valley, Catamarca Province. MACN-Pv 8400, mandible in lateral view (from Kraglievich 1948). B. Neocavia sp. from the lower levels of the Monte Hermoso Formation, Montehermosan Stage/Age, early Pliocene, Farola Monte Hermoso locality, Buenos Aires Province. MD-FM-17-01, mandible fragment in labial (B1), lingual (B2), and occlusal (B3; B4, explanatory drawing) views. C. “Neocavia despressidens” Parodi and Kraglievich, 1948 from upper? levels the Monte Hermoso Formation, early Pliocene, Farola Monte Hermoso locality, Buenos Aires Province. MLP 46-V-13-53, mandible in lateral view and molariform series in occlusal view (from Parodi and Kraglievich 1948). Abbreviations: ap, alveolar protuberances; chin, mandibular symphysis; ias, incisive alveolar sheath; nMpi, notch for the insertion of the tendon of the masseter medialis pars infraorbitalis muscle.

Fig. 1. A. Location map indicating the geographic distribution of Neocavia localities in Argentina. B. Encalilla and Andalhuala localities, Santa María Valley, Tucumán, and Catamarca provinces, respectively. C. Caleufú locality, La Pampa Province. D. Farola Monte Hermoso locality, Buenos Aires Province.

Fig. 3. Caviid rodent Neocavia lozanoi Kraglievich, 1932 from the late Miocene–early Pliocene of northwest Argentina, Andalhuala Formation, “Araucanense”: Andalhuala locality, Santa María Valley, Catamarca Province, Argentina (A, C) and Encalilla locality, Santa María Valley, Tucumán Province (B). A. MACN-Pv 8400, skull with left P4–M3 and right P4–M2 (A1–A4), right mandibular fragment with incisor p4–m2, and m3 broken (A5–A7). B. PVL 7057, maxillary fragment with left and right P4–M2. C. MACN-Pv 8415, left mandibular fragment with p4–m2. In dorsal (A1), ventral (A2, B1), lateral (A3, A4, B2), labial (A5, C1), lingual (A6, C2), and occlusal (A7, C3) views. Abbreviations: nMpi, notch for the insertion of the tendon of the masseter medialis pars infraorbitalis muscle. Scale bars 5 mm.

Fig. 2. Measurements used in the comparative analysis A. Skull of Microcavia australis, Recent. B. Third left upper molar (M3) C. First right lower premolar (p4; anterior to left). Abbreviations: Cranial measurements: APB, anteromedial-posterorlateral length of tympanic bullae; APL, length of premaxillary-maxillary suture to anterior border of foramen magnum; BO, width of the anterior half of the basioccipital; BP, anteroposterior length of the posterior part of the diastema; IF, length of incisive foramina; MXL, length from the premaxillary-maxillary suture to the posterior portion of the M3 projection; UDL, upper diastema length from alveolar posterior margin of incisor to alveolar anterior margin of P4; WBc, width of basicranial. Dental measurements: LAP, anteroposterior length of molariforms; LLA, anteroposterior length of anterior lobe of molariforms; LPL, anteroposterior length of posterior lobe of molariforms; PLE, posterolabial extension of anterior lobes; WAL, mediolateral length of anterior lobe of molariforms; WPL, mediolateral length of posterior lobe of molariforms.