A NEW SUPERFAMILY OF ENIGMATIC CRABS (CRUSTACEA: DECAPODA) FROM THE CRETACEOUS OF COLOMBIA, AND ITS IMPACT ON THE BRACHYURA

A new monophyletic superfamily of enigmatic crabs is described based on recently discovered specimens from the Cenomanian (~94 million years ago) of Colombia, South America. Forty–two specimens were collected from mass mortality and appendage–rich surfaces, in association with other crustaceans including modern cumaceans and shrimps. The exceptional degree of preservation of the new taxon has permit the description of complete dorsal and ventral features, claws, all walking legs, sexually dimorphic abdomen, pleopods, mouthparts, and large compound eyes, allowing comparison with fossil and extant decapods. A brachyuran affinity is supported by the possession of a symmetric abdomen lacking uropods and articulated rings, short antennae and antennulae that are located between the eyes, possession of only one pair of chelae, therefore pereiopods or walking legs achelate, and last pereiopod visible. In addition, kinship with ancient members within the Subsection Raninoida is suggested by the dorsally exposed first abdominal somites, fusiform carapace, bifid rostrum, spanner–like chelipeds with fixed finger deflected ~90º, paddle–like achelate pereiopods, non–prehensile fifth pair of legs carried subdorsally, and apparent absence of thoracic sexual openings. However, its particular bauplan (e.g., dorsal characters and unique sternal configuration) is matchless among any known fossil or extant brachyuran crabs, meriting the erection of the new superfamily. The functional morphology of carapace, mouthparts and limbs of this taxon suggests an agile marine burrower and swimmer, well suited for predatory/scavenging purposes. This new taxon provides valuable information on the macroevolutionary patterns among ancient crabs, and enhances our understanding on the role of the Neotropics on the origin and diversification of brachyuran lineages during Cretaceous times