Placenticeras

Placenticeras is an ammonite genus from the Late Cretaceous. Its fossils have been found in Asia, Europe, North and South America.

Taxonomy
Placenticeras, named by Fielding Bradford Meek, 1870, is the type genus for the Placenticeratidae, a family that is part of the Hoplitaceae, a superfamily of the Ammonitida.

Description
Placenticeras has a very involute shell with slightly convex sides and a very narrow venter. Side are smooth or with faint sinuous ribs. Early whorls have umbilical tubercles that in later whorls appear higher on the sides. Earlier whorls normally have lower and fine upper ventrolateral clavi. Ornament weakens in the adult and the last whorl may be smooth. The suture is with numerous adventitious and autxiliary elements, with saddles and lobes that are much frilled.