A natural cast of a Triassic turtle shell

Natural molds and impressions of invertebrate shells, devoid of remains of skeletal tissues, are common fossils. In the case of large vertebrate bones, such a mode of preservation is, however, rare. The paper presents a natural external mold of a turtle plastron from the Triassic Löwenstein Formation of Germany. The specimen represents an exceptionally large individual, larger than the known representatives of Proterochersis robusta from the same formation and close in size to P. porebensis from the Grabowa Formation of Poland. On its surface, impressions of lesions are present which likely represent traces left by ectoparasites.

Illustration: Plastron of a middle-sized individual of Proterochersis robusta (middle) and the described specimen: natural mold of the external surface of plastron (right) and virtual positive (left).