Classification Kingdom Animalia Sub kingdom Invertibrata Phylum Mollusca Class Cephalopoda Order Nautiloidea Genus Nautilus Morphological characters – Shell is Globular and involute coiling Few whorls with large body chamber, Aperture is oval and rarely semilunar Umbilicus may be occluded with callus. Central siphuncle is present with septal neck-retrosiphonate. Shows simple nauitiloid suture line, thin growth lines and simple ribs. Geological Age – Triassic to recent