Interpreting character variation in turtles: Araripemys barretoi (Pleurodira: Pelomedusoides) from the Araripe Basin, Early Cretaceous of Northeastern Brazil

The Araripe Basin (Northeastern Brazil) has yielded a rich Cretaceous fossil fauna of both vertebrates and invertebrates found mainly in the Crato and Romualdo Formations, of Aptian and Albian ages respectively. Among the vertebrates, the turtles were proved quite diverse, with several specimens retrieved and five valid species described to this date for the Romualdo Fm. There were also records of turtles from Ipubi and Crato Fms., mainly fragmentary material which precluded proper specific identification; however, Araripemys barretoi is supposed to occur on both Crato and Romualdo Fms. Here we describe thirteen specimens of A. barretoi - including the first description of an almost complete individual, bearing a skull, from the Crato Fm. We report a great amount of morphological variation, interpreted as being essentially of intraspecific nature, including individual, sexual and ontogenetic variation.