Evolution and phylogeny of Pleurodira (Testudines) with the description of a new species of Bairdemys (Podocnemidae) from the middle Miocene of Venezuela

Abstract

Though neglected for a long time, one of the two lineages of Testudines (turtles and tortoises) the Pleurodira has been attracting the researchers, whose articles usually deal with descriptions of new species (extant and extinct), behavior or feeding habits, or phylogenetic analyzes of one of the subgroups of Pleurodira, Chelidae or Pelomedusoides, the latter subdivided in two lineages with extant taxa: Pelomedusidae and Podocnemidae. There some phylogenetic analyzes with terminal taxa from the main groups of Pleurodira, but only with molecular data. Therefore, a morphological data analysis containing taxa from all the clades of this group, including fossils, is necessary to better understand the evolutionary history of this lineage. In this dissertation, I describe a new species of Bairdemys (Podocnemidae) from the middle Miocene of Venezuela, and I include it in a phylogenetic analysis with extensive taxonomic sampling, including taxa from all the lineages of Pleurodira. This analysis is based on morphological characters (new and previously proposed ones) and it is the largest exclusive phylogenetic analysis ever made for Pleurodira, allowing inferences about the general patterns of diversification and morphology of the group. At the same time, the new described táxon shows morphological characters that, along with geological aspects of its type locality, allow inferences about a marine wave of diversification of Podocnemidae during the Cenozoic, which achieved great success, specially by the end of Oligocene and beginning of Miocene.