A neptunoceratid cephalopod, Texanoceras jacksboroensis n. gen. n. sp., is described from the Virgilian (Upper Pennsylvanian) Graham and Caddo Creek Formations in Texas, North America. The family Neptunoceratidae was previously represented by a single genus, Tetrapleuroceras. This new material provides important emendations to the diagnostic concept of the enigmatic family including shell orientation, mature modification and siphuncular structure. Although higher taxonomic position of Neptunoceratidae is difficult to determine at present, morphologic similarities between the family and the orthoceratid (?) family Brachycycloceratidae are discussed.