Taphonomy and palaeoecology of decapod crustaceans from Oligocene and Early Miocene fish beds of the Central and Eastern Paratethys

Abstract

ABSTRACT Records of decapod taxa reported from Oligocene and Early Miocene fish beds of the Central and Eastern Paratethys have been reviewed in order to discuss taphonomic features at selected localities. In total, 120 specimens originating from 30 localities in Azerbaijan, the Czech Republic, Hungary, Poland, Romania, Russia, Slovenia, and Ukraine were studied. The identified crab taxa include majoids (Platymaia lethaea, Majoidea indet.) and portunoids (Liocarcinus spp., Necronectes sp., Portuninae indet., Thalamitinae indet., Portunidae indet.). Brachyuran crabs in fish beds are typically preserved as flattened (near-)complete individuals. In most cases, the preserved crabs represent corpses, whereas clearly identifiable moults are present only at 5 of the 30 studied localities. The preservation of (near-) complete decapod bodies requires calm depositional conditions and a quick burial. At some localities, the dominance of corpses over moults suggests animals swimming close to the bottom under anoxic/dysoxic conditions and reaching an area with low oxygen levels causing their death with subsequent rapid burial. At other locations, the dominance of moults was observed suggesting crabs living close to the place of burial. In these cases, crabs were reported mostly from the beds with numerous fish skeletons, suggesting crabs being major macroscavengers of fish remains.