Eogeryon elegius n.gen. and n.sp (Decapoda: Eubrachyura: Portunoidea), one of the oldest modern crabs from late Cenomanian of the Iberian Peninsula

A new Heterotremata (Eubrachyura) decapod from the late Cenomanian of Condemios de Arriba (Guadalajara, Spain) is described. The new taxon has affinities with the basal portunoids and their features suggest placement within the Portunoidea. Comparisons with all the currently known Cretaceous Eubrachyura taxa demonstrates how Eogeryon elegius is an advanced crab in spite of its Cenomanian origins, suggesting that it evolved from ancestors previously unknown according to the current fossil record. As a result of those comparisons, a new family, Eogeryonidae, within Portunoidea, is proposed to accommodate the new genus and species. In addition, Eogeryon elegius is also compared with early Eocene and extant related taxa, with emphasis on the non-swimming portunoid family Geryonidae. Eogeryon elegius appears to be an ancestor of most derived forms of Portunoidea, suggesting that the evolution of Eubrachyura must have occurred at least during the Early Cretaceous.