A freshwater crab Potamon (Brachyura: Potamidae) from the middle Miocene Lake Bugojno (Gračanica, Bosnia and Herzegovina), with notes on potamid taphonomy

The middle Miocene site of Gračanica in Bosnia and Herzegovina, where limnic sediments of the former Lake Bugojno are exposed, yielded remains of a crab. The single specimen represents a freshwater brachyuran classified in the open nomenclature as Potamon sp. With an age of ~ 15 Ma, the Gračanica specimen is the oldest Potamon occurrence from southern Europe. An articulated female individual with preserved pereiopods suggests autochthonous or parautochthonous nature of the specimen. Presence of cuticular disks in the studied specimen confirms that these structures, previously identified in decayed crab specimens in actualistic taphonomic experiments, can be preserved in the fossil record. If found isolated, the disks may confirm the presence of decapods in studied assemblages and can be considered an additional tool for identification of otherwise rare freshwater crab fossils.