A new turtle taxon (Podocnemidoidea, Bothremydidae) reveals the oldest known dispersal event of the crown Pleurodira from Gondwana to Laurasia

Abstract

Pan-Pleurodira is one of the two clades of extant turtles (i.e. Testudines). Its crown group, Pleurodira, has a Gondwanan origin being known from the Barremian. Cretaceous turtle fauna of Gondwana was composed almost exclusively of pleurodires. Extant pleurodires live in relatively warm regions, with a geographical distribution restricted to tropical regions that were part of Gondwana. Although pleurodires were originally freshwater forms, some clades have adapted to a nearshore marine lifestyle, which contributed to their dispersal. However, few lineages of Pleurodira reached Laurasian regions and no representatives have so far been described from the pre-Santonian of Laurasia, where the continental and coastal Cretaceous faunas of turtles consist of clades exclusive to this region. A new turtle, Algorachelus peregrinus gen. et sp. nov., is described here from the southern Laurasian Cenomanian site of Algora in Spain. Numerous remains, including a skull and well-preserved postcranial specimens, are attributed to this species. The abundant shell elements, much more numerous than those known in most members of pleurodiran clade Bothremydidae, allow its variability to be studied. The new taxon represents the oldest evidence of the occurrence of Pleurodira in Laurasia, and is the oldest genus of the abundant and diverse Bothremydodda so far described. Factors such as the relatively high Cenomanian temperatures, the adaptation of this Gondwanan clade to coastal environments, and the geographical proximity between the two landmasses may have contributed to its dispersal. This finding shows that the first dispersals of Pleurodira from Gondwana to Laurasia occurred much earlier than previously thought.http://zoobank.org/urn:lsid:zoobank.org:pub:8FD358A5-53BD-4308-828A-AC6802184185