UNUSUAL PLEON ORNAMENTATION IN THE CLAWED LOBSTER, HOPLOPARIA (NEPHROPIDAE), FROM TURONIAN SHALE DEPOSITS OF THE WESTERN INTERIOR SEAWAY

Two new species of clawed lobster referable to Hoploparia,“Hop W” and “Hop P”, from the Late Cretaceous (middle Turonian) Carlile Shale of the Black Hills region of South Dakota and Wyoming have very similar cephalothoraxes but pleons that are distinctly different and unusually ornate for the genus. Pleon morphology might, at first, suggest a phylogenetic connection to Nephrops, but Hoploparia and Nephrops have been determined by traditional systematic and cladistic methods to be only distantly related. Cladograms indicate that the unusual, transversely banded pleon condition is a convergent, not homologous, feature in Nephrops and “Hop W”. The two morphologies, “Hop W” and “Hop P”, are interpreted as different species, as opposed to sexual (or ecophenotypic or other) dimorphs of the same species. Both morphologies occur at some localities. The two morphologies are of roughly equal abundance, suggesting sexual dimorphism, but the authors know of no similar sexual dimorphism in modern lobsters.