Nautilida Agassiz 1847

Order Nautilida Agassiz, 1847 Diagnosis Exogastrically curved or coiled nautiloids with a conch shape ranging from gyroconic or cyrtoconic to more or less tightly coiled. Shell surface smooth or sculptured with a variety of elements (ribs, nodes, spines, longitudinal ridges or lines). Septa simply domed in most species, with the shape of the whorl profile producing suture lines with variable lobes and saddles. Variations in septal shape with inflexions producing deep lobes in some genera. Septal necks short and straight, rarely slightly widened. Connective rings cylindrical or beaded. Siphuncular or cameral deposits absent. Juvenile conch with cup-shaped initial chamber and narrow siphuncle. Morphological evolution includes the degree of coiling, the shape and size of the juvenile and adult conch and the suture line (after Shimansky 1962b; emended). Included suborders Nautilina Agassiz, 1847 (Jurassic to Recent); Solenochilina Flower, 1950 (Carboniferous to Permian); Liroceratina Flower, 1955 (Carboniferous to Jurassic); Rutoceratina Shimansky, 1957 (Devonian); Tainoceratina Shimansky, 1957 (Carboniferous to Triassic); Temnocheilina Flower, 1963 (Devonian to Permian); Domatoceratina Korn, 2025 (Carboniferous to Triassic).