New material of “Eurysternidae” (Thalassochelydia, Pan-Cryptodira) from the Kimmeridgian of the Swiss Jura Mountains

Abstract

The region of Porrentruy (Swiss Jura Mountains) is known for its rich and diverse assemblage of Late Jurassic coastal marine turtles (Thalassochelydia). Dominated by the "Plesiochelyidae", this assemblage also includes representatives of the two other thalassochelydian groups, the "Thalassemydidae" and "Eurysternidae." In this study, we present new shell-based material from Porrentruy referable to eurysternids. One specimen represents a juvenile individual or a relatively small taxon, and is notably characterized by a well fenestrated plastron exhibiting a wider than long central plastral fontanelle. Two other specimens are much larger and possibly represent the largest eurysternids known to date. The fourth specimen is characterized by a unique plastral morphology otherwise only known in very small juveniles. This is the first time this unique plastral morphology is known to persist in an adult or subadult. The new material described herein represents at least three distinct taxa, all of them probably new. However, we refrain from naming new species based on this incomplete material in order to avoid adding confusion to an already complex taxonomical situation. This study provides new insights into the great diversity of eurysternids during the Late Jurassic.

A new species of the large-headed coastal marine turtle Solnhofia (Testudinata, Thalassochelydia) from the Late Jurassic of NW Switzerland

“…Among similarities with So. parsonsi, we can mention the presence of reduced costo-peripheral fontanelles, wide vertebral scales, hyoplastra about as wide as long, and a well ossified plastron with central and lateral fontanelles (for a global comparison with other eurysternids, see Anquetin et al, 2017;Püntener et al, 2020). Two main anatomical characteristics differentiate So.…”

“…This level is rich in vertebrate and wood remains (e.g., Philippe et al, 2010;Leuzinger et al, 2017a,b;Püntener et al, 2017b;Schaefer et al, 2018). The better part of the turtle remains from the Porrentruy region comes from the Lower Virgula Marls (Anquetin et al, 2015;Püntener et al, 2015Püntener et al, , 2017aPüntener et al, , 2020.…”

“…However, some taxa are known to reach a carapace length of up to 400 mm (Joyce, 2003;Anquetin and Joyce, 2014) or even more (Püntener et al, 2020). The available material of So.…”