Styrionautilus

Styrionautilus is a genus of nautiloids and first of the Clydonautilidae with a range extending from the Middle Triassic, Anisian to the Upper Triassic, Norian. Its fossils have been found in North America (Nevada), Europe, and Timor.

Styrionautilus Temporal range: Middle-Late Triassic (Nor)
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	Nautilida
Family:	†Clydonautilidae
Genus:	†Styrionautilus Mojsisovics, 1902

In general form Styrionautilus is similar to other clydonautilids, smooth and involute. The suture however is more primitive. The ventral saddle is straight across without modification of a median lobe.

Styrionautilus may be derived from Indionautilus or similar form included in the Liroceratidae. In turn Styrionautilus is the likely ancestor of Proclydonautilus, Cosmonautilus, and/or Callaionautilus