Burrow morphology of the land crab Gecarcinus lateralis and the ghost crab Ocypode quadrata on San Salvador Island, The Bahamas: comparisons and palaeoenvironmental implications

Abstract

Burrow morphologies of the land crab Gecarcinus lateralis and the ghost crab Ocypode quadrata were investigated on East Beach, San Salvador Island, The Bahamas, with the goals of critical comparison of their morphologies and of clarifying and advancing their palaeoenvironmental usefulness. In comparing land crab burrows to those of the ghost crab, the former are simpler but more variable in overall shape. G. lateralis burrows have a more compressed form in the transverse section of the burrow shaft and possess lower (more horizontal) shaft inclination than those of O. quadrata. In the late Holocene backshore and dune deposits on San Salvador, two types of fossil burrows were observed. On the basis of the morphologic differences documented herein between modern burrows of land and ghost crab species, one fossil burrow form can be interpreted as having been produced by G. lateralis and the other (trace fossil Psilonichnus upsilon) produced by O. quadrata. Because the modern burrows of these crabs are different not only in shape but also in their environmental preference, the occurrence of trace fossils comparable to burrows of the land crab and ghost crab (P. upsilon) could be used as indicators of vegetated coastal dunes (land crab burrows) and beach backshore (near sea level; ghost crab burrows) palaeoenvironments