Bitaunioceras is a Permian

Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

 michelinocerin orthocerid

Orthocerida

Orthocerida is an order of extinct nautiloid cephalopods also known as the Michelinocerda that lived from the Early Ordovician possibly to the Late Triassic . A fossil found in the Caucasus suggests they may even have survived until the Early Cretaceous...

 with a gradually expanding orthoconic shell with straight transverse sutures and a small, orthochoanitic, subcentral siphuncle

Siphuncle

The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and Spirula...

.

The shell surface of Bitaunioceras has a few, shallow, rounded constrictions and numerous, unequal, prominent transverse lirae. Septal necks in the siphuncle are short and straight, connecting rings are cylindrical.

Bitaunioceras species have been found in Texas in the United States, Coahuila in Mexico, Sicily, Timor, and the south Urals in Russia.

References

• Sweet, Walter C. 1964. Nautiloidea-Orthocerida. Treatise on Invertebrate Paleontology
  Treatise on Invertebrate Paleontology
  The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...
  
  , Part K. Geological Soc of America, and Univ Kansas Press.