Benacoceras
Encyclopedia
Benacoceras is a strongly ribbed, evolute ammonite
from the Late Jurassic, coiled so that all whorls are exposed. Ribbing is biplicate, with very short secondaries. The venter, the outer rim, is smooth, at least on the outer whorl.
Ammonitida
The Ammonitida is an order of more highly evolved ammonoid cephalopods from the Jurassic and Cretaceous time periods, commonly with intricate ammonitic sutures....
from the Late Jurassic, coiled so that all whorls are exposed. Ribbing is biplicate, with very short secondaries. The venter, the outer rim, is smooth, at least on the outer whorl.