 Arietites

Arietites is a genus of massive, giant evolute, psiloceratacean ammonites in the family Arietitidae in which whorls are subquadrate and transversely ribbed and low keels in triplicate, separated by a pair of longitudinal grooves, run along the venter.Fossils are known world wide from the lower Sinemurian stage of the Lower Jurassic.