''Placenticeras'' is a genus of

ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

s from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

. Its

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s 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 ...

, 1870, is the type genus for the Placenticeratidae, a family that is part of the Hoplitoidea, a superfamily of the

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

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

Species list according t

* ''

Placenticeras bidorsatum ''Placenticeras'' is a genus of ammonites 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 Placenticera ...

'' * ''

Placenticeras costatum ''Placenticeras'' is a genus of ammonites 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 Placenticera ...

'' * ''Placenticeras cumminsi'' * ''

Placenticeras fritschi ''Placenticeras'' is a genus of ammonites 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 Placenticera ...

'' * ''

Placenticeras grossouvrei ''Placenticeras'' is a genus of ammonites 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 Placenticera ...

'' * ''Placenticeras intercalare'' * ''

Placenticeras kolbajense ''Placenticeras'' is a genus of ammonites 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 Placenticera ...

'' * ''

Placenticeras maherndli ''Placenticeras'' is a genus of ammonites 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 Placenticerati ...

'' * ''

Placenticeras mediasiaticum ''Placenticeras'' is a genus of ammonites 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 Placenticera ...

'' * ''

Placenticeras memoriaschloenbachi ''Placenticeras'' is a genus of ammonites 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 Placenticera ...

'' * '' Placenticeras meeki'' * '' Placenticeras orbignyanum'' * ''

Placenticeras paraplanum ''Placenticeras'' is a genus of ammonites 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 Placenticera ...

'' * ''

Placenticeras placenta ''Placenticeras'' is a genus of ammonites 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 Placenticera ...

'' * ''

Placenticeras polyopsis ''Placenticeras'' is a genus of ammonites 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 Placenticera ...

'' * ''Placenticeras pseudoplacenta'' * '' Placenticeras semiornatum'' * '' Placenticeras syrtale'' (syn. '' Stantonoceras pseudocostatum'') * '' Placenticeras tamulicum'' * '' Placenticeras vredenburgi'' * ''Placenticeras whitfieldi'' File:Placenticeras costatum, Cretaceous, Pierre Shale Formation, Cheyenne River, Pennington County, South Dakota, USA - Houston Museum of Natural Science - DSC02011.JPG, ''P. costatum'', Pierre Shale Formation, South Dakota File:Placenticeras placenta (fossil ammonite) (Upper Cretaceous; western North America) 1.jpg, ''P. placenta'' with mosasaur bite marks File:Placenticeras meeki, Late Cretaceous, Pierre Shale Formation, Rosebud County, Montana, USA - Houston Museum of Natural Science - DSC01924.JPG, ''P. meeki'' showing sutures File:Placenticeras intercalare at the American Museum of Natural History.jpg, ''P. intercalare'' ammolite,

Bearpaw Formation The Bearpaw Formation, also called the Bearpaw Shale, is a geologic formation of Late Cretaceous (Campanian) age. It outcrops in the U.S. state of Montana, as well as the Canadian provinces of Alberta and Saskatchewan, and was named for the Bear ...

, Alberta, Canada File:Placenticeras UMMNH.jpg, ''P. whitfieldi'' with mosasaur bite marks File:Placenticeras sp. (fossil ammonite) (Pierre Shale, Upper Cretaceous; Meade County, South Dakota, USA) 1.jpg, ''Placenticeras'' sp. showing sutures.

Pierre Shale The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico. The Pierre Shale was described by Fielding Bradford Meek, Meek a ...

Upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cret ...

; Meade County,

South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state, state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Dakota people, Dakota Sioux ...

( USA)

References

* Arkell ''et al.'', 1957, Mesozoic Ammonoidea,

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...

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

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