Published online by Cambridge University Press: 14 July 2015
Pharkidonotus megalius n. sp. is described from the Desmoinesian of the Mud Springs Mountains, New Mexico. This unusually large bellerophontid reaches a length of at least 90 mm and is also characterized by a prominent high median ridge bearing a narrow selenizone and subdued collabral ornamentation on the whorl surface at all stages of growth. Its size and subdued ornamentation are quite different from that of the two previously known North American Pennsylvanian species of Pharkidonotus. Although steinkerns of comparable size have been reported from several localities in North America, the specimens discussed here are the first relatively well preserved shells of very large Pennsylvanian bellerophontids to be described.