Systematics and paleoecology of Miocene brachyuran crabs (Decapoda: Brachyura: Cancroidea, Portunidae) from the St. Marys Formation, Maryland, USA

A collection of decapod fossils from the Miocene St. Marys Formation, Little Cove Point Member (Maryland, USA), yielded six species belonging to three genera of brachyuran crabs, Necronectes A. Milne-Edwards, 1881, Callinectes Stimpson, 1860, and Cancer Linnaeus, 1758. Cancer included four species, Cancer irroratus Say, 1817; C. borealis Stimpson, 1859; and two new species, C. nancei and C. zahrae. Necronectes is represented by N. drydeni Rathbun, 1935,. Callinectes was also represented by a single species, C. sapidus Rathbun, 1896. Most of the fossils were small relative to normal adult size, suggesting that the environment served as a nursery to developing individuals. The paleoecology of Chesapeake Bay was similar to the present-day ecology based on study of recent faunas, lithology, and paleoecology. The paleoenvironment was a shallow embayment within the temperate climate zone.