Redescription of the rare Late Cretaceous ammonite Chesapeakiceras nodatum, from the Chesapeake and Delaware Canal, USA

ABSTRACT. The heteromorphic ammonite Chesapeakiceras nodatum Kennedy and Cobban, 1993, has been known only from the late Santonian to early Campanian Merchantville Formation of the Atlantic Coastal Plain of the United States. Prior to this report, only three fragmentary specimens have been recovered from the Chesapeake and Delaware Canal in the state of Delaware, U.S.A. Here we describe a fourth specimen, NJSM GP23099, that is the most complete known fragment of C. nodatum and is the only existing specimen that has been recovered “in situ”. This demonstrates that the stratigraphic range of C. nodatum extends into the upper Merchantville Formation.