Nuevos datos sobre el crecimiento de la tortuga <i>Toremys cassiopeia</i> en las X Jornadas Internacionales de Salas de los Infantes

En esta edición de las Jornadas se presentó el trabajo “Ontogenetic Insights into the Iberian Pleurosternid Toremys cassiopeia: New Specimens from the Lower Albian of Ariño (Spain)”, realizado en colaboración entre el Grupo de Biología Evolutiva de la UNED y la Fundación Conjunto Paleontológico de Teruel-Dinópolis, con la participación de varios investigadores de ambas instituciones. El estudio da a conocer nueve nuevos ejemplares del pleurostérnido Toremys cassiopeia, hallados en el yacimiento albiense de Ariño (Teruel). Estos incluyen, por primera vez, individuos juveniles que permiten reconstruir una secuencia de crecimiento para esta especie. El resumen es el siguiente:

Pleurosternidae is a clade of freshwater paracryptodiran turtles recorded from the Kimmeridgian (Upper Jurassic) to the Albian (Lower Cretaceous) in North America and Europe. Despite recent advances in their taxonomy and diversity (particularly in the Iberian Peninsula with the description of Selenemys lusitanica, Riodevemys inumbragigas, Toremys cassiopeia, and Pleurosternon moncayensis) ontogenetic trajectories within the group are still poorly understood. Our knowledge of intraspecific variation within this lineage also remains relatively limited, with the notable exception of Pleurosternon bullockii, which has been recently investigated in detail. This lack of data has contributed to persistent ambiguities in the anatomical interpretation and phylogenetic placement of several pleurosternid taxa.
Toremys cassiopeia was described from the lower Albian bonebed of Ariño (Teruel, Spain), and represents the stratigraphically youngest known pleurosternid worldwide. Thus, it is currently the only pleurosternid taxon confirmed beyond the Berriasian extending the stratigraphic range of the group. Until now, T. cassiopeia was only known from adult or subadult specimens, limiting developmental interpretations.
In this context, this study presents shells and shells remains of nine unpublished specimens of T. cassiopeia from the same Albian bonebed (i.e., from the type locality of the taxon), representing different ontogenetic stages, including several identifiable as juveniles. These specimens offer, for the first time in the Iberian record, a detailed ontogenetic series for a pleurosternid turtle. The comparative analysis of juvenile and adult morphologies provides critical insights into developmental changes in shell architecture and diagnostic traits across ontogeny. These results contribute to refining the diagnosis of T. cassiopeia and clarifying its intraspecific variability across ontogeny. Furthermore, the ontogenetic patterns observed are compared with those recently documented for Pleurosternon bullockii, from the British Berriasian record, providing a broader evolutionary and paleobiogeographic framework for understanding developmental trends within Pleurosternidae. Thus, by documenting ontogenetic patterns in T. cassiopeia, this study also emphasizes the need to take growth-related variation into account within the systematic frameworks of fossil turtles (an essential step toward resolving long-standing taxonomic uncertainties within Pleurosternidae).