Ricardo A. Bonini

Ancient DNA from the extinct South American giant glyptodont Doedicurus sp. (Xenarthra: Glyptodontidae) reveals that glyptodonts evolved from Eocene armadillos

Glyptodonts were giant (some of them up to ~2400 kg), heavily armoured relatives of living armadillos, which became extinct during the Late Pleistocene/early Holocene alongside much of the South American megafauna. Although glyptodonts were an important component of Cenozoic South American faunas, their early evolution and phylogenetic affinities within the order Cingulata (armoured New World placental mammals) remain controversial. In this study, we used hybridization enrichment and high‐throughput sequencing to obtain a partial mitochondrial genome from Doedicurus sp., the largest (1.5 m tall, and 4 m long) and one of the last surviving glyptodonts. Our molecular phylogenetic analyses revealed that glyptodonts fall within the diversity of living armadillos. Reanalysis of morphological data using a molecular ‘backbone constraint’ revealed several morphological characters that supported a close relationship between glyptodonts and the tiny extant fairy armadillos (Chlamyphorinae). This is surprising as these taxa are among the most derived cingulates: glyptodonts were generally large‐bodied and heavily armoured, while the fairy armadillos are tiny (~9–17 cm) and adapted for burrowing. Calibration of our phylogeny with the first appearance of glyptodonts in the Eocene resulted in a more precise timeline for xenarthran evolution. The osteological novelties of glyptodonts and their specialization for grazing appear to have evolved rapidly during the Late Eocene to Early Miocene, coincident with global temperature decreases and a shift from wet closed forest towards drier open woodland and grassland across much of South America. This environmental change may have driven the evolution of glyptodonts, culminating in the bizarre giant forms of the Pleistocene.

Primer registro de Equus neogeus en río Abaucán (Catamarca, Argentina)

espanolEn el presente trabajo se describen restos de caballos del Pleistoceno procedentes de afloramientos en el rio Abaucan de la localidad de Tinogasta (Catamarca). El estudio comparativo se realizo con los registros conocidos de este grupo de mamiferos en America del Sur y se identifico comoEquus neogeus. Es el primer registro de esta especie en el Pleistoceno tardio de Catamarca (Argentina). Estos datos representan un nuevo registro de Equidae en America del Sur y aportan nuevas evidencias sobre su cronologia y distribucion geografica.Equus neogeus es el caballo mas grande y mas gracil de los de America del Sur y se encuentra en su zona mas oriental. Hasta ahora no se habian registrado fuera de las tierras bajas de Argentina, Uruguay y Brasil. Este es el primer registro en regiones mas altas altitudinalmente. Ademas, el contexto litoestratigrafico permite obtener consideraciones paleoecologicas. Desde el punto de vista cronoestratigrafico los niveles fosiliferos se refieren a la edad Lujaniense. EnglishThe fossil vertebrate record in Catamarca province is widely recognized in the Neogene deposits, but the quaternary mammal records are poorly represented. Here, we describe remains of fossil horses from Pleistocene sediments outcropping in the Abaucan River in the locality of Tinogasta. A comparative study was made with the known record of these groups of mammals in South America, identifying the remains asEquus neogeus, which constitutes the first records of this species for the Late Pleistocene of Catamarca (Argentina). These data increase the record of Equidae in South America and provide new evidence about the chronological and geographical distribution.Equus neogeus is the largest and slenderest morphotype of the South American horses, and occurs in eastern South America, but does not recorded outside of lowland Argentina, Uruguay, and Brazil. This is the first record in the higher altitude regions. In addition, the lithostratigraphic context was analyzed, allowing paleoecological considerations. The chronostratigraphic context recognize that the carrier levels are referable to the Lujanian Age.

A New Guinea Pig (Rodentia, Caviomorpha) from Northwestern Argentina: Implications for the Origin of the Genus Cavia

ABSTRACT We describe a new caviomorph rodent, Cavia cabrerai, sp. nov. (Caviidae, Caviinae), from the upper levels of Andalhuala Formation (San Fernando Norte locality, Catamarca Province, northwestern Argentina), which represents the oldest fossil record of the genus. The new species differs from extant and extinct species of Cavia by a unique combination of characters: large size, proportionally anteroposteriorly elongated molars, slightly anteroposteriorly compressed prisms, relatively shallow primary lingual flexids, abundant cement in the lingual flexids, and anterolingual widening of the second crests of cheek teeth. A phylogenetic analysis indicates that Cavia cabrerai, sp. nov., is the sister taxon of extant Cavia species and displays dental characters more plesiomorphic than the latter. Some characters of C. cabrerai, sp. nov., namely, compression of prisms and depth of flexids, are morphologically intermediate between the related extinct Caviinae Palaeocavia and the extant species of Cavia. An ash bed dated at 4.72 ± 0.08 Ma that overlies the fossiliferous level of the new material supports the presence of Cavia close to the Miocene-Pliocene boundary. The origin of Cavia may have been triggered by the expansion of relatively open and arid environments that arose near the Miocene-Pliocene boundary.