ASSESSING THE PRESERVATION POTENTIAL OF GECARCINID LAND CRABS (DECAPODA, BRACHYURA, GECARCINIDAE) FROM SAN SALVADOR, THE BAHAMAS

Land crabs (Decapoda, Brachyura, Gecarcinidae) have been found in marine and terrestrial sediments of Pleistocene and Holocene age throughout the Caribbean. A taphonomic analysis of land crab remains assessed the preservation potential of two widespread and abundant species, Gecarcinus lateralis and G. ruricola. Field surveys were conducted three times a week for four weeks along the northern coast of San Salvador Island, the Bahamas, at three localities that varied in vegetation cover, available sediment, and wind and wave energy. More than 1,400 identifiable remains were found and scored for four taphonomic characters: fragmentation, edge modification, surface alteration, and color loss.

Only four completely articulated crabs were found. The majority of specimens exhibited various levels of disarticulation, from complete limbs to only podomeres remaining. Overall, there was relative overrepresentation of claws, and the distribution of recovered remains differed significantly (p < 0.0001) from the distribution expected based on the anatomy of a single crab (8 legs, 2 claws and 1 carapace per individual).

The proportion of remains affected by fragmentation, surface alteration, and color loss varied significantly across localities. Remains found in direct sunlight and open spaces were consistently more fragmented, had more surface alteration and more color loss than those found within vegetation or on the beach. Edge modification did not differ significantly across localities (p = 0.045).

The quantity and preservation of surficial crab remains found suggests that gecarcinid land crabs, particularly their claws, survive short-term taphonomic filters such as scavenging and weathering, and therefore should have the potential to be preserved. Indeed, small (2.5 gallon) samples from Holocene sediments along two outcrops coast of San Salvador have revealed four propodi and three complete chelae. Further work focused on the long-term taphonomy of terrestrial crustaceans is needed to fully understand the preservational potential of fossil land crabs.