Placenticeras is a genus of from the Late Cretaceous. Its 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
Hoplitoidea, 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 auxiliary elements, with saddles and lobes that are much frilled.
Species
Species list according to
[1]:
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Placenticeras bidorsatum
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Placenticeras costatum
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Placenticeras cumminsi
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Placenticeras fritschi
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Placenticeras grossouvrei
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Placenticeras intercalare
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Placenticeras kolbajense
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Placenticeras maherndli
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Placenticeras mediasiaticum
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Placenticeras memoriaschloenbachi
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Placenticeras meeki
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Placenticeras orbignyanum
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Placenticeras paraplanum
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Placenticeras placenta
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Placenticeras polyopsis
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Placenticeras pseudoplacenta
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Placenticeras semiornatum
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Placenticeras syrtale (syn. Stantonoceras pseudocostatum)
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Placenticeras tamulicum
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Placenticeras vredenburgi
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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, 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, 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,
Upper Cretaceous; Meade County,
South Dakota (
USA)
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Arkell et al., 1957, Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology Part L. Geological Soc. of America, Univ of Kansas Press. R.C. Moore, (Ed)
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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.
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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.
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Discovering Fossils: How to Find and Identify Remains of the Prehistoric Past (Fossils & Dinosaurs) by Frank A. Garcia, Donald S. Miller, and Jasper Burns
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Placenticeras in the Paleobiology Database
