A Valanginian crustacean microcoprolite ichnofauna from the shallow-marine hydrothermal vent site of Zengővárkony (Mecsek Mts., Hungary)

Abstract

A rich and diverse crustacean microcoprolite ichnofauna is reported from the Valanginian of the Mecsek Mts., Hungary. Localities from the Bolondut and Dezső Rezső valleys near Zengővarkony (Eastern Mecsek Mts.) provided Favreina aff. dispentochetarius, Palaxius darjaensis, P. triochetarius,P. salataensis, P. tetraochetarius, and P. decaochetarius. They occur in limonitic and partly metasomatized limestones, limestone olistoliths, and ammonite body-chambers. The remarkable richness of this ichnofauna plus the previous records from the same environment (altogether 11 ichnospecies of four ichnogenera from a single stratigraphic level) make it the most diverse crustacean ichnofauna of the Mesozoic. The former ecosystem of the ichnofauna is considered a deeper shallow-marine (water depth <300 m) hydrothermal vent on which the producers of the microcoprolites lived. The related brachiopod fauna shows a remarkable size and is dominated by Lacunosella. This fauna is not similar to typical fossil deep-sea vent faunas; however, it offers a thorough understanding of other fossil shallow-marine hydrothermal vent faunas and the role of crustaceans in these ecosystems. This is the first record of crustacean coprolites from such a fossil site and documents that crustaceans were diverse and played an important role in shallow-marine, non photosynthesis-based ecosystems in the geological past.