North American Glyptodontines (Xenarthra, Mammalia) in the Upper Pleistocene of northern South America

The Glyptodontidae is one of the most conspicuous groups in the Pleistocene megafauna of the Americas. The Glyptodontinae were involved in the Great American Biotic Interchange (GABI) and their earliest records in North America are about 3.9 Ma, suggesting an earlier formation of the Panamanian landbridge. Taxonomically it is possible to recognize two Pleistocene genera of Glyptodontinae:Glyptodon (ca. 1.8 – 0.008 Ma), restricted to South America, andGlyptotherium (ca. 2.6 – 0.009 Ma), including records in both North and Central America. Here we present the first report of the genusGlyptotherium in South America, from the Late Pleistocene of several fossil localities in Falcón State, northwestern Venezuela. A comparative analysis of the material, represented by cranial and postcranial parts, including the dorsal carapace and caudal rings, suggests a close affinity withGlyptotherium cylindricum (Late Pleistocene of Central Mexico). This occurrence in the latest Pleistocene of the northernmost region of South America Supports the bidirectional faunal migration during the GABI and the repeated re-immigration from North America of South American clades, as has been reported in other members of the Cingulata (e.g., Pampatheriidae)

Diversification trajectories and evolutionary life-history traits in early sharks and batoids

Different interpretations on the timing of early diversification and radiation of modern sharks and batoids (Neoselachii) in the Earth's history exist and are related to discrepancies in taxonomic and phylogenetic interpretations favouring a Late Triassic or earliest Jurassic diversification and subsequent radiation event, respectively. Sampling standardization based on pooled taxonomic occurrences made it possible to overcome the problem of a much richer neoselachian record in the Late Jurassic than earlier on. The standardized pattern of genus richness is one of low and fairly constant diversity in the Late Triassic and earliest Jurassic with a steep rise in the Toarcian (ca 180 Myr ago), representing the maximum diversification rate in the Jurassic towards a Middle and Late Jurassic plateau. The major Toarcian diversification agrees with the conclusions based on phylogenetic analyses, but is in conflict with older interpretations based on raw data. Early Jurassic expansion of neoselachians was opportunistic in the aftermath of the end-Triassic mass extinction and the reasons for their rapid diversification and radiation probably include small body size, short lifespans and oviparity, enabling faster ecological reorganizations and innovations in body plans for adapting to changing environmental conditions