''Placenticeras'' is a genus of

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish ...

s from the Late Cretaceous. Its fossils have been found in Asia, Europe, North and South America.

Taxonomy

''Placenticeras'', named by

Fielding Bradford Meek Fielding Bradford Meek (December 10, 1817 – December 22, 1876) was an American geologist and a paleontologist who specialized in the invertebrates. Biography The son of a lawyer, he was born in Madison, Indiana. In early life he was in bu ...

, 1870, is the type genus for the

Placenticeratidae Placenticeratidae is an extinct family of mostly Late Cretaceous ammonites (cephalopod order Ammonitida) included in the superfamily Hoplitoidea, derived from the Engonoceratidae by an increase in suture complexity. Placeticeratids are charac ...

, a family that is part of the

Hoplitoidea Hoplitoidea, formerly Hoplitaceae, is a superfamily of mostly Upper Cretaceous ammonites comprising families united by a similar suture pattern with multiple similar elements that tend to decrease in size going toward the umbi ...

, a superfamily of the

Ammonitida Ammonitida is an order of ammonoid cephalopods that lived from the Jurassic through Paleocene time periods, commonly with intricate ammonitic sutures. Ammonitida is divided into four suborders, the Phylloceratina, Lytoceratina, Ancylocerat ...

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 auxiliary elements, with saddles and lobes that are much frilled.

Species

Placenticeratidae - Placenticeras whitfieldi

Species list according t

* ''Placenticeras bidorsatum'' * ''Placenticeras costatum'' * ''Placenticeras cumminsi'' * ''Placenticeras fritschi'' * ''Placenticeras grossouvrei'' * ''Placenticeras intercalare'' * ''Placenticeras kolbajense'' * ''Placenticeras maherndli'' * ''Placenticeras mediasiaticum'' * ''Placenticeras memoriaschloenbachi'' * ''

Placenticeras meeki ''Placenticeras meeki'' is an ammonite species from the Late Cretaceous. These cephalopods were fast-moving nektonic carnivores. They mainly lived in the American Interior Basin (Western Interior Seaway). Description Shells of this species could ...

'' * ''Placenticeras orbignyanum'' * ''Placenticeras paraplanum'' * ''Placenticeras placenta'' * ''Placenticeras polyopsis'' * ''Placenticeras pseudoplacenta'' * ''Placenticeras semiornatum'' * ''Placenticeras syrtale'' (syn. ''Stantonoceras pseudocostatum'') * ''Placenticeras tamulicum'' * ''Placenticeras vredenburgi'' * ''Placenticeras whitfieldi''

References

* Arkell ''et al.'', 1957, Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology Part L. Geological Soc. of America, Univ of Kansas Press. R.C. Moore, (Ed) * W. A. Cobban and Hook, S. C. 1983 Mid-Cretaceous (Turonian) ammonite fauna from Fence Lake area of west-central New Mexico. Memoir 41, New Mexico Bureau of Mines&Mineral Resources, Socorro NM. * W. A. Cobban and Hook, S. C. 1979, ''Collignoniceras woollgari wooollgari'' (Mantell) ammonite fauna from Upper Cretaceous of Western Interior, United States. Memoir 37, New Mexico Bureau of Mines&Mineral Resources, Socorro NM. * Discovering Fossils: How to Find and Identify Remains of the Prehistoric Past (Fossils & Dinosaurs) by Frank A. Garcia, Donald S. Miller, and Jasper Burns
''Placenticeras''
in the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Pal ...

Placenticeratidae Ammonitida genera Late Cretaceous ammonites Cretaceous animals of Asia Ammonites of Europe Ammonites of North America Ammonites of South America {{ammonitina-stub