A new Iberian pleurosternid (Jurassic-Cretaceous transition, Spain) and first neuroanatomical study of this clade of stem turtles

A partial skeleton of a pleurosternid turtle (Paracryptodira), from the Jurassic-Cretaceous transition at the Spanish locality of agreda (Moncayo Region, Soria Province), is presented here. Its partial skull represents the third of this lineage to be recognised in the European record, with the previously known specimens corresponding to British species. The specimen of Pleurosternidae studied here is attributed to a new species, Pleurosternon moncayensis. This lineage of stem turtles is identified as the most abundant and diverse group of freshwater aquatic turtles in Europe for the stages adjacent to the Jurassic-Cretaceous transition. Its presence decreased radically at post-Berriasian levels, when freshwater lineages of Eucryptodira, of Asian origin, are identified as the dominant forms at these aquatic turtle faunas. The confirmation of Pleurosternidae as freshwater inhabitants is made here, through the first neuroanatomical study for this lineage. Thus, the neuroanatomical reconstruction of Pleurosternon moncayensis sp. nov. is the first to be carried out for a freshwater stem turtle, and it allows us to identify convergent adaptations with freshwater members of the crown Testudines.

Automated summary

This study presents a partial skeleton of a pleurosternid turtle, attributed to a new species Pleurosternon moncayensis, from the Jurassic-Cretaceous transition in Spain. It is the third lineage of pleurosternids recognized in Europe, with previous specimens found in British species. The research confirms the Pleurosternidae as freshwater inhabitants through the first neuroanatomical study for this lineage, showing convergent adaptations with freshwater members of crown Testudines.