Anatomía y variabilidad del caparazón de Neochelys zamorensis en las XXXVIII Jornadas de la SEP

Otro de los trabajos presentados en las XXXVIII Jornadas de la Sociedad Española de Paleontología, recientemente celebradas en Valencia, trataba también sobre tortugas de la Cuenca del Duero. Concretamente sobre una segunda especie de la pleurodira Neochelys, definida en la provincia de Zamora. Se trata de Neochelys zamorensis, una especie más antigua que Neochelys salmanticensis y de menor tamaño. Hasta ahora solamente un ejemplar atribuible a esta especie ha sido analizado, de manera preliminar. Sin embargo, la limitada información sobre ese holotipo, correspondiente a un carapazón relativamente completo, hace que esta forma sea actualmente mal conocida.

Numerosos carapazones completos, parciales y, especialmente, centenares de placas sueltas, son identificadas tanto en la localidad tipo de Neochelys zamorensis como en otros afloramientos de la mima provincia, con una datación similar. Este material parece compatible con una única especie. Así, su análisis no sólo permitirá conocer en detalle la anatomía del caparazón de la especie, y proponer una diagnosis actualizada y válida para la misma, sino también el potencial análisis de aspectos relativos al desarrollo ontogenético, dimorfismo sexual y variabilidad individual. El estudio preliminar sobre estos aspectos ha sido defendido en el citado congreso científico especializado, siendo el título de la ponencia: “Shell anatomy and variability of the Spanish podocnemidid turtle Neochelys zamorensis”. El resumen del trabajo es el siguiente:

Although Europe is not part of the current distribution of Pleurodira, members of this lineage are recognized in the fossil record of this continent, being well-represented in both the Late Cretaceous and the Eocene records. The most abundant and diverse representative of Pleurodira in European Cenozoic levels is Neochelys. This podocnemidid turtle is recognized as a freshwater taxon exclusive to the Eocene record of this continent. Several species of Neochelys have been defined based on findings made in lower and middle Eocene outcrops in various European countries. The Spanish taxa, from the middle Eocene of the Duero Basin, are the two youngest. The first of these two species that was described is Neochelys salmanticensis, from the Bartonian of the Salamanca Province. The other is Neochelys zamorensis, from the Lutetian of the Zamora Province. Knowledge about the former has recently increased such a precise shell characterization, based on many individuals. In fact, the species was identified as represented by a number of individuals noticeably larger than that known for any other species of the genus. In contrast, the information on Neochelys zamorensis continues to be extremely limited, and only its holotype was presented in a preliminary way. Very abundant shell material from various Lutetian localities in the Zamora Province (i.e., the type locality corresponding to Sanzoles, and other synchronous outcrops, located in the Cubillos-Monfarracinos area), much more abundant than that recently described for Neochelys salmanticensis, is analysed here. In addition to isolated plates, these remains include various well-preserved partial and complete shells, corresponding to individuals at different ontogenetic stages. As a result of this study, an amended diagnosis for Neochelys zamorensis can be proposed, but also shell variability (considering individual, ontogenetic and sexual variability) is analysed and characterised considering several carapacial and plastral remains.

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Más información:

• Referencia: Pérez-García, A., Guerrero, A., Martín de Jesús, S., Ortega, F. 2023. Shell anatomy and variability of the Spanish podocnemidid turtle Neochelys zamorensis. In Ros-Franch, S., Paredes-Aliaga, M. V., Martínez-Pérez, C. (Eds.), Libro de Resúmenes de las XXXVIII Jornadas SEP. Palaeontological Publications, 4, 185.