Oxycerites

Oxycerites is an extinct ammonoid cephalopod belonging to the haploceratoid family, Oppeliidae, that lived during the Middle Jurassic.
Shells of "Oxycerites" are involute, compressed and generally smooth with a sharply rounded venter on the outer rim, deeply impressed dorsum on the inner rim, and a small umbilicus. 
The living chamber takes up slightly more than half a whorl. "Oxycerites" grew to a diameter of at least 17.5 cm, about 7 inches.
"Oppelia" and "Oecotraustes" are similar and closely related forms. "Oppelia" is smoother, "Oecotraustes" more strongly ribbed
Distribution.
Jurassic of Argentina, France, Germany, Iran, Madagascar, Russia, Saudi Arabia and the United Kingdom