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

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.

KEYWORDS:

• Anoxic/dysoxic conditions
• brachyuran crabs
• palaeoenvironment
• taphonomy

Acknowledgments

The research of OK and ZB was carried out as part of the research project supported by a grant from the National Academy of Sciences of Ukraine (0121U110402). The research of MH was supported by the Slovak Research and Development Agency (APVV-17-0555, APVV-20-0079) and Hungarian Scientific Research Fund (OTKA K112708). Field excavations of IG were sponsored by the National Geographic Society of the USA, grant #9869-16. The research of TP was supported by the Institute of Geology of the Czech Academy of Sciences (RVO67985831). M. Melinte-Dobrinescu provided data on nannofossils. We are thankful to Sylvain Charbonnier (Muséum National d’Histoire Naturelle, Paris, France), Carrie E. Schweitzer (Kent State University at Stark, North Canton, USA), and an anonymous reviewer for their constructive comments. We express our thanks to the editor G. Dyke for his effective management of our submission. We also wish to thank Ş. Vasile (University of Bucharest, Romania) for his kind help during the preparation of the manuscript. R. Gregorová (Moravian Museum, Brno, the Czech Republic), I. Kania (University of Rzeszów, Poland) and K. Palotás (Mining and Geological Survey of Hungary, Budapest) are acknowledged for providing access to the material deposited at the respective institutions.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Hungarian Scientific Research Fund [OTKA K112708]; National Academy of Sciences of Ukraine [0121U110402]; National Geographic Society (U.S.) [9869-16]; Institute of Geology of the Czech Academy of Sciences [RVO67985831]; Slovak Research and Development Agency [APVV-17-0555, APVV-20-0079].