An almost complete side-necked turtle shell (Pelomedusoides, Bothremydidae) from the Maria Farinha Formation (Paleogene, Paleocene), Paraíba Basin, NE Brazil

Background. Pelomedusoides turtles are an important group in extant fauna of northern South America, Africa and Madagascar, which have a long fossil record, with numerous records through the Cretaceous, Paleogene, and Neogene in South America. One of high- diversified clade of this linage is Bothremydidae, and its record extends from Early Cretaceous (Barreminan) to Eocene. So far, no named species from the Paleocene of Brazil were described. The single Paleocene record is a peripheral bone associated to pelomedusoid turtle from the Maria Farinha Formation (Danian), of Pernambuco State. Herein we present an almost complete shell (DGM 1310LE) from the Maria Farinha Formation, Paraíba Basin, which is the first early Paleocene South American bothremydid turtle. Methods. The new specimen have been analyzed through traditional paleontological methodology. We performed a CT scan in DGM 1310LE in search for internal bones and structures. In addition, we scored DGM 1310LE in a modified data matrix of Pelomedusoides, with 43 taxa and 175 characters, and the phylogenetic analysis were performed in TNT. Branch supports were provided using bootstrap and Bremer support. Results. The new specimen is the most complete turtle coming of Maria Farinha Formation. DGM 1310LE has seven neurals, and an incomplete neural series to suprapygal, as the most Podocnemidoidae turtles. Our preliminary phylogeny resulted in 4 most parsimonious trees of 428 steps. The strict consensus tree places DGM 1310LE as a member of Bothremydidae, which was recovered in a polytomy together with early Cretaceous turtle Galianemys. 5th Turtle Evolution Symposium Rio de Janeiro, RJ, Brazil | July, 2015 Discussion. Despite of the almost complete nature of the DGM 1310LE, we were unable to determine if DGM 1310LE is a new species due to the lack of diagnostic characteristics. However, this new Paleocene specimen is important because it expands the record of Bothremydidade to the Cenozoic of Brazil; up to date only the Early Cretaceous genera Cearachelys and Atolchelys were recognized. Moreover, Bothremydidae shows a great diversification, occupying marine environments as well as diverse freshwater environments. Since the depositional context of the Maria Farinha Formation is considered a shallow marine environment (continental shelf), including the presence of marine taxa such as lamniforms sharks (e.g. Cretolamna appendiculata) and the dyrosaurid crocodyliform Guarinisuchus munizi, the presence of a Bothremydidae in these strata confirm the great paleoecological diversification of this family, varying from near-shore marine to freshwater environments.