The Nautilitoidea is a superoder within the subclass Nautiloidea, comprizing the phylogenetically related Nautilida, Oncocerida, and Tarphycerida.

The superorder has its roots in the Bassleroceratidae

Bassleroceratidae

The Bassleroceratidae is a family of gradually expanding, smooth ellesmerocerids with a slight to moderate exogastric curvature, subcircular to strongly compressed cross section, and ventral orthochaonitc siphuncle. The ventral side is typically more sharply rounded than the dorsal side and septa...

, the ancestoral family of the Tarphycerida, sometimes included in the Ellesmerocerida. The Bassleroceratidae also gave rise to the Granciloceratidae, the ancestral family of the Oncocerida, which in turn gave rise to the Nautilida which includes the Nautilidae which includes the living Nautilus

Nautilus

Nautilus is the common name of marine creatures of cephalopod family Nautilidae, the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in two genera, the type of which is the genus Nautilus...

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By having the ancestral Bassleroceratidae in the Tarphycerida, the Nautilitoidea becomes monophyletic. With the Bassleroceratidae in the Ellesmerocerida the Tarphycerida becomes distinct from the oncocerid-nautilid lineage, making the Nautilitoidea polyphyletic.