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

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 RESUMEN Las morfologias de las madrigueras del cangrejo rojo terrestre, Gecarcinus lateralis, y del cangrejo fantasma, Ocypode quadrata, se investigaron en la playa del Este (East Beach) de la isla de San Salvador (Bahamas) con el objetivo tanto de diferenciarlas defi nitivamente entre si como de clarifi car y avanzar en la comprension de su signifi cado paleoambiental. Al comparar las madrigueras de los cangrejos terrestres con las de los cangrejos fantasma, se observa que las primeras son mas simples pero mas variables en morfologia. La seccion transversal de las madrigueras de G. lateralis presenta una forma mas comprimida que la observable en las madrigueras de O. quadrata, asi como su inclinacion, mas horizontal en la parte inferior. En los depositos dunares y de backshore del Holoceno tardio de San Salvador se han diferenciado dos tipos de madrigueras fosiles. A partir de las diferencias morfologicas observadas entre las madrigueras de las especies actuales de los cangrejos fantasma y terrestres podria interpretarse que uno de estos tipos de madrigueras fosiles fue