Tainoceratoidea Hyatt 1883

Superfamily Tainoceratoidea Hyatt, 1883 Diagnosis Superfamily of the suborder Tainoceratina with a discoidal to pachyconic, subinvolute or subevolute conch. Whorl profile always with midventral longitudinal groove; in early species subquadrate with a distinct ventrolateral shoulder and a distinct umbilical margin, in derived species polygonal with divergent or convergent flanks. Dorsal whorl zone always very small. Sculpture with rows of ventrolateral nodes, in some species with rows of nodes on the flank. Septa simply domed; suture line depending on the whorl profile, usually with shallow lobes and low saddles. Included family Tainoceratidae Hyatt, 1883 (Late Carboniferous to Early Triassic; 23 Palaeozoic genera, 89 Palaeozoic species). Remarks The superfamily Tainoceratoidea as used here corresponds to the family Tainoceratidae as employed by earlier authors. It is generally regarded as one of the most important Late Carboniferous to Triassic nautiloid clades. Its family composition and internal classification have been discussed repeatedly over the last 90 years, and various concepts for the differentiation of the genera have been presented. As many of the other families of the suborder are placed within the Pleuronautiloidea, only one family is accepted here: Tainoceratidae Hyatt, 1883 – Forms with usually octagonal whorl profile; sculpture usually with several rows of nodes (Fig. 30).