No abstract

No abstract

Caviomorph rodents, the New World Hystricognathi, are one of the most characteristic groups of South American mammals. Although they have been in the continent at least since the middle Eocene, those of the Deseadan Land mammal Age (early-late Oligocene) are the best source to understanding their early history due of their good record, large geographic distribution and good temporal calibration of many of the local faunas. Here, we describe the following new taxa from the classical locality of Cabeza Blanca: Octodontoidea Acaremyidae Galileomys baios n. sp., Octodontoidea incertae sedis Ethelomys loomisi n. gen., n. comb., Acarechimys leucotheae n. sp., Protacaremys? adilos n. sp., Chinchilloidea incertae sedis Loncolicu tretos n. gen., n. sp., Incamys menniorum n. sp., Caviomorpha incertae sedis Llitun notuca n. gen., n. sp., Leucokephalos zeffiae n. gen., n. sp. and Cephalomyidae Cephalomys ceciae n. sp. The DP4 of an 'eocardiid', Asteromys punctus? is described for the first time. These new taxa allow us to reinterpret the relationships of some of the previously known Deseadan species and genera. They show a great early diversification at least for extra Andean Patagonia, involving at least three of the main caviomorph lineages: octodontoids, chinchilloids and cavioids.

We report a new vertebrate assemblage from the Pliocene Vergel Member of the San Gregorio Formation in northwestern Venezuela, which includes Crocodylia and Testudines indet., toxodonts, at least four species of xenarthrans of the Dasypodidae, Pampatheriidae, Glyptodontidae and Megatheriidae, and rodents. The last are Cardiatherium, cf. Caviodon (Hydrochoeridae), Neoepiblema (Neoepiblemidae), and what is here described as a new genus of a low-crowned octodontoid. cf. Caviodon is the first cardiomyine for northern South America. The rodent assemblage resembles in its ecological composition those of the late Miocene (Huayquerian) from the "Mesopotamian" of Argentina and the Acre region in Brazil, with partially overlapping systematic composition. The stratigraphic position of the San Gregorio Formation and mammals other than caviomorphs suggest a late Pliocene age for these sediments, implying the endurance of rodent taxa beyond their biochron in southern South America.

No abstract

No abstract

No abstract

Caviomorphs (South American hystricognaths) are recorded in the continent since the middle Eocene. The middle Eocene-early Oligocene is considered a key moment for their evolutionary history because by the early Oligocene they were differentiated into four superfamilies: Octodontoidea, Cavioidea, Chinchilloidea and Erethizontoidea. Due to their generalized dental patterns and abundance in the fossil record, Octodontoidea are interesting for analysing the origin and early history of caviomorphs. The phylogenetic relationships of the earliest octodontoids are studied herein. Results confirmed a basal caviomorph diversification in the middle Eocene (c. 45 Mya), with one lineage leading to Pan-Octodontoidea, and another leading to Erethizontoidea, Cavioidea and Chinchilloidea, which is not in accordance with analyses based on molecular data. Three major radiations were identified: the first one (late Eocene?/early Oligocene?) occurred in low latitudes with the differentiation of Pan-Octodontoidea and the earliest crown-Octodontoidea. The second radiation (late Oligocene) was a large-scale South American event; in the southernmost part of the continent it is recognized as the first Patagonian octodontoid radiation, which provided the characteristic high morphological disparity of the superfamily. The third radiation (late Miocene) is characterized by the replacement of 'old' by 'modern' octodontoids; the nature of this third event needs to be study in a broader taxonomic context.