Pleurodiras migrando a Europa en la 15 edición del congreso Gondwana

Continuamos con algunas de las presentaciones relacionadas con la paleontología de vertebrados que tuvieron lugar en el congreso Gondwana 15. A la presentación “An update on the diachronous migration to Europe of several Gondwanan lineages of pleurodiran turtles” le corresponde el resumen:

Extant turtles belong to two lineages: Pleurodira and Cryptodira. Pleurodira are principally characterized by sutured contacts between pelvis and shell, and the acquisition of horizontal neck retraction. They principally developed in Gondwana, while Cryptodira spread through Laurasia (Lapparent de Broin, 2000). Pleurodira are now restricted to relatively warm regions, with a more limited geographical distribution than Cryptodira. They now basically live in freshwater environments, usually of intertropical areas, in continents that formed part of Gondwana: Africa, South America and Oceania. The relative position of the landmasses, and variations in global temperatures, resulted in changes in their distributions. Pelomedusoides are Gondwanan pleurodires, known from the Early Cretaceous. Their most abundant and diverse representatives are Bothremydidae and Podocnemididae, both recognized in the European record.

The fauna of freshwater turtles from the Early Cretaceous of Europe was mainly composed by Laurasiatic Cryptodira. However, Pleurodira experienced a significant development in the Late Cretaceous, with the introduction of marine taxa adapted to freshwater environments (Pérez-García, 2012). At least some of these Gondwanan pleurodires belong to Bothremydini (sensu Gaffney et al., 2006), a clade of Bothremydidae that probably reached Europe before the Santonian.

A single specimen of Pelomedusoides has been identified in the Paleocene of Europe: the French Taphrosphys ambiguus (see Broin, 1977). It belongs to another clade of Bothremydidae: Taphrosphyini. It was found in a marine environment. Paleocene sites with continental fauna are rare and always exhibit Laurasiatic taxa.

The greatest European diversity of Pelomedusoides is recorded in the Eocene. More than a dozen species of Podocnemididae are identified, all corresponding to the African clade Erymnochelyinae.

The European post-Eocene record of Pleurodira is extremely limited. Only two specimens have been cited. “Chrysemys” montolivensis, from the Oligocene of France, was initially attributed to Cryptodira. Broin (1977) reassigned it to Pelomedusoides, pointing to its possible affinity with Bothremydidae in subsequent papers. The other is the holotype of Nostimochelone lampra, from the Early Miocene of Greece. The limited available information does not allow a precise determination.

The European record represents several diachronic migrations of African pleurodires to Europe. The transformation of several lineages from originally continental forms to littoral taxa facilitated the dispersion. Some of these migrations were very successful. A review of the taxa involved, and the study of abundant unpublished material (including several new taxa), allow us to improve knowledge of the systematics and paleobiogeography of these forms.

------
Más información:

• Referencia: Pérez-García, A.; de Lapparent de Broin, F. 2014. An update on the diachronous migration to Europe of several Gondwanan lineages of pleurodiran turtles. In: Pankhurst, R.J., Castiñeiras, P., Sánchez Martínez, S. (Eds.). Abstract Book of Gondwana 15, North meets South: 137.
• Imágenes: En la superior, caparazón del representante de Bothremydidae del Cretacico Superior de Europa Iberoccitanemys convenarum; en la inferior, espaldar del podocnemídido del Eoceno europeo Neochelys laurenti.