Aspidostephanus

Aspidostephanus is an extinct cephalopod genus belonging to the ammonite subclass, included in the perisphinctacean family Olcostephanidae that lived during the earliest Cretaceous and possible latest Jurassic. Fossils of the genus have been found in France, the Balearics, North Africa, and Argentina.
The shell of "Aspidostephanus" is depressed with a broad smooth venter. Early whorls have strong lateral ribs with umbilical and lateral tubercles; later whorls smooth except for tubercles at the umbilicus. Whorl height increases with age. "Aspidostephanus" is similar to but broader than its close relative, "Spiticeras".