Archaeoportunus isabenensis, a new genus and species of portunoid crab (Crustacea, Decapoda) from the lower Eocene of Huesca (Spain)

Resumen

Crabs recovered from
marly strata of the upper Roda Formation (lower Cuisian, Ypresian)
at Isábena (Huesca, Spain) exhibit a clear set of characters, mainly
in chelipeds and dorsal carapace that favour their assignment to the
superfamily Portunoidea, and confirm a close relationship with the
family Portunidae. However, the presence of important and easily
distinguishing features, such as the strongly marked dorsal ridges
or notably narrow sternum, lead us to propose a new genus and
species, Archeoportunus isabenensis n. gen., n. sp., and a new
family, the Archaeoportunidae n. fam. The ventral features of the
new taxon, particularly the fairly narrow sternum which notably
becomes even narrower posteriorly, the strongly downturned sternites
1-4 bearing strong swellings, and the general adaptation of sternum,
abdomen and pereiopods, substantiate the basal condition of the new
taxon within the Portunoidea and also contributes to current
knowledge of evolutionary issues within that group