Crabs as overlooked trace fossil makers in frreshwater settings

RICARDO NESTOR MELCHOR; JORGE FERNANDO GENISE; JUAN D. FARINA; MARÍA VICTORIA SÁNCHEZ; LAURA SARZETTI; GRACIELA VISCONTI

Lepe, España

Workshop; Worshop on Crustacean Bioturbation, fossil and Recent; 2010

Universidad de Barceloma, Universidad de Huelva, Ayuntamiento de Lepe

The trace fossil record of true crabs (Decapoda: Brachyura) from nonmarine settings is limited to a few tentative assignments of fossil burrows from fluvial successions. This is in contrast with the recognition of a number of trace fossils assigned to freshwater burrowing crayfishes (Camborygma, Loloichnus, Lunulichnus, Dagnichnus and one species of Cellicalichnus), and with the several ichnotaxa assigned to marine or nearshore brachyuran decapod crustaceans, including Psilonichnus, Skolithos, Thalassinoides, Gyrolithes, Macanopsis, Spongeliomorpha and Foersterichnus (e.g. Frey et al., 1984). The rarity of trace fossils of freshwater crabs is also surprising if we consider that modern freshwater crabs account for about the 20% of the known extant crab species (Yeo et al., 2008) and that they play a significant role in the mixing of sediments. In this contribution we describe a new fossil burrow that is confidently attributed to freshwater crabs on the basis of neoichnological studies, which pose some questions about the scarce trace fossil record of freshwater crabs and give clues for the identification of their burrows in the fossil record.