THE OLDEST RECORD OF PALAEOCAVIA AMEGHINO (MAMMALIA, RODENTIA, CAVIIDAE) FOR THE LATE MIOCENE OF CATAMARCA, ARGENTINA

MADOZZO JAÉN M. CAROLINA; ORTIZ, P. E.; NASIF, NORMA

Mendoza

Congreso; 4Th International Paleontological Congress; 2014

Asociación Paleontológica Argentina

Caviid rodents are conspicuous elements of the living South American small mammal communities. However, although its neogene fossil record is relatively rich, many aspects of the early evolution of the group are unknown. The extinct genus Palaeocavia is represented in Argentina by six species recorded in Entre Ríos (Ituzaingó Formation, late Miocene), La Pampa (Cerro Azul Formation, late Miocene), Buenos Aires (Pliocene), Córdoba (?Formación Pampeana?, Pleistocene), Jujuy (Maimará Formation, late Miocene-early Pliocene), and Catamarca provinces (Andalhuala Formation, late Miocene). Here we describe the oldest record for the genus, coming from levels of El Jarillal Member (Chiquimil Formation), croping out near Villavil, Catamarca, northwestern Argentina. This unit underlies the Andahuala Formation, therefore the bearing levels are older than the 7.14 Ma limit between the two formations. The material corresponds to a fragment of left mandible with p4-m3. Molariforms are euhypsodont and bilobated, with each lobe showing a slight constriction on its labial apex in occlusal view. The p4 and m3 are respectively the smallest and the largest teeth of the series; m1 and m2 are subequal in size. The anterior lobe is smaller than the posterior one in all teeth; additionally, the lingual furrow of the posterior lobe is wide, shallow, and situated on its anterior edge. The hypoflexid is wide and deep, showing parallel edges on its internal portion; nevertheless, the lingual end of this flexid is deeper on its anterior side, forming a bezel-like outline. Interprismatic cement covers the internal third of the hypoflexid. The enamel layer is continuous on the labial side of p4-m3; besides, it is absent only on the postero-lingual corner of the posterior lobe of p4 and m1 (the poor preservation prevents the observation of this feature on m2-m3). The anterior lobe of the p4 is obliquely arranged regarding the antero-posterior axis of the mandible and there is no evidence of the additional anterior elongation, being both features diagnostic characters of Palaeocavia. The genus was listed for other late Miocene sites but these remains never were described or figured. The presence of Palaeocavia in Villavil in dated levels confirms its existence since at least this age. Several facts such as the absence of taxonomic revisions of the genus (none of its species have been re-studied since their original descriptions), the loss of holotypes of several nominal forms, and the uncertain stratigraphic provenance of some remains, make the redefinition of the genus mandatory.