Nautilida

Nautilida is an order of generally coiled nautiloid cephalopods that first appeared in the mid Paleozoic era and survives to the present day. The order was historically far more diverse, with between roughly 22 and 34 families and 165 to 184 genera recognized across its history, but only a single family survives today, Nautilidae, made up of two genera, Nautilus and Allonautilus, with six living species between them. Living nautilids are now restricted to the tropical Indo-Pacific, a much smaller range than the order held in the past.