Occurrence of the marine turtle Thalassemys in the Kimmeridgian of Oker, Germany

Marinheiro, J., & Mateus O. (2011).  Occurrence of the marine turtle Thalassemys in the Kimmeridgian of Oker, Germany. 71st Annual Meeting of the Society of Vertebrate Paleontology. 151., Jan: Abstracts of the 71st Annual Meeting of the Society of Vertebrate Paleontology


A partial chelonian was collected from the Langenberg Formation quarry of Oker (near Goslar, Lower Saxony, Germany). The amniotes from this formation include other chelonians (possible Plesiochelyidae), the sauropod Europasaurus holgeri, theropods (Velociraptorinae), crocodylomorphs (Atoposauridae, Theriosuchus pusillus, Goniopholis simus, Machimosaurus hugii, Steneosaurus brevirostris) and pterosaurs (Dsungapteridae, ?Ornithocheiroidea, ?Ctenochasmatidae).

The reported specimen, DFMMh/FV 296, includes a skull part (articulated quadrate, squamosal, basisphenoid, and pterygoid), a disarticulated 40 cm long partial carapace, plastron, and one cervical vertebra.

The carapace bears fontanelles, trapezoidal suprapygal with straight edges, small last neurals

a plicated longitudinal pattern in the proximal end of the costals originating on the posterior side of the scute sulci and dissipating posteriorly, wide central opening in the plastron, xiphiplastra with little or no contact between each other, and both the hyo- and hypoplastron have digit-form buttress projections.

The specimen has a central plastra fontanelle, which is regarded as a feature of the clade including [....], Santanachelys, and Thalassemys. DFMMh/FV 296 differs from

edges and xiphiplastron participation in the central fontanelle is autapomorphic for the Thalassemys genus. A large central fontanelle with hyo and hypoplastron polygonal medial
contact between xiphiplastra and reduced size of the two last neural plates is shared between T. hugii and the Oker specimen. DFMMh/FV 296 differs from this species due to the presence of plastral projections. The different shape of the plastron (no polygonal-like margins or hyo- and hypoplastron projections) suggests that T. moseri [....]
ent genus. Therefore, we can assign this specimen to Thalassemys sp.