Un pleurostérnido soriano en las VIII Jornadas de Salas de los Infantes

Varios trabajos sobre tortugas mesozoicas presentados en las VIII Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno estaban centrados en material ibérico. En uno de ellos se revisó el registro español y portugués del linaje de tortugas de agua dulce Pleurosternidae, presentándose nuevo material que incluye el primer cráneo ibérico, correspondiendo al segundo de este grupo para el conjunto de Europa, ya que, hasta ahora, únicamente la especie británica Pleurosternon bullockii era conocida por esa región anatómica.

El resumen del trabajo es el siguiente:

One of the most abundant and diverse freshwater groups of turtles in the Upper Jurassic and Lower Cretaceous levels of Europe is Pleurosternidae. It corresponds to a lineage of Paracryptodira with a wide palaeobiogeographic distribution, being known in both North America and Europe, its larger stratigraphic range having been identified in this last continent. The Iberian record of this lineage was very poorly known until a few years ago, and only scarce remains attributable to indeterminate forms of Pleurosternidae have been traditionally recognized. The recent discovery of several new specimens has allowed to identify a wide diversity, three new taxa having been described: the Upper Jurassic Selenemys lusitanica and Riodevemys inumbragigas, and the Lower Cretaceous Toremys cassiopeia. All these Iberian forms are exclusively known by elements of the postcranial skeleton, especially by the shell.

A new finding is presented here, corresponding to several elements attributable to a single turtle specimen. This finding comes from the locality of Ágreda, in the Soria Province (Autonomous Community of Castile and Leon), this town being located in the eastern Cameros Basin. The specimen has been collected in the upper part of the Tera Group, in a level probably belonging to the Matute Formation, being Tithonian-early Berriasian in age. This formation was deposited in a fluvio-lacustrine environment, during the Jurassic-Cretaceous transition.

The characters available in the new specimen presented here allow its attribution to a paracryptodiran representative and, more specifically, to Pleurosternidae. This is the first evidence on this clade documented not only in the Autonomous Community of Castile and Leon but also in the Cameros Basin, being the oldest record of a turtle documented in this basin. In addition to shell elements, the new specimen preserves the posterior half of the skull. The information about the cranial skeleton of Pleurosternidae is very limited. Thus, only a single skull was so far known for the European record, being attributable to the Lower Cretaceous species Pleurosternon bullockii, from Great Britain. The comparison of the new skull with that of the British taxon is carried out here. In addition, the detailed study of the preserved elements of both the carapace and the plastron is carried out, based on the first-hand study of all taxa so far defined in Europe. The relatively good preservation of the outer surface of several of the bony elements of the specimen from Ágreda (considering both some regions of the skull as well as the plates), allows us to carry out the comparative study with the ornamentation patterns known for the other members of Pleurosternidae, this character having been recognized as of high interest from a systematic perspective. Thus, the precise systematic attribution of the new specimen within Pleurosternidae is discussed.

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Más información:

• Referencia: Pérez-García, A., Canudo, J.I., Castanera, D. 2019. New data on the Iberian record of pleurosternid turtles based on the finding of the first representative of this clade in the Cameros Basin (Spain). Póster. Libro de resúmenes del VIII Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno: 109.
• Imagen: Fotografía, en vistas dorsal y ventral, del único cráneo de Pleurosternidae hasta ahora conocido en Europa.