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An iridescent ammonite from Madagascar Map of North America highlighting the shallow inland sea present during the mid-Cretaceous period. Ammolite comes from the fossil shells of the Upper Cretaceous disk-shaped ammonites Placenticeras meeki and Placenticeras intercalare, and (to a lesser degree) the cylindrical baculite, Baculites compressus.
Ammonites. Smithsonian Institution Press. ISBN 978-1-58834-024-5. Walker, Cyril and Ward, David. Fossils. Dorling, Kindersley Limited, London, 2002. A Broad Brush History of the Cephalopoda by Dr. Neale Monks, from The Cephalopod Page. Ammonite maturity, pathology and old age By Dr. Neale Monks, from The Cephalopod Page. Essay about the life ...
Douvilleiceras is a genus of ammonites from the Middle to Late Cretaceous. Its fossils have been found worldwide, in Africa , Asia , Europe , and North and South America . Description
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.
Shell of Pleuroceras spinatum can reach a diameter of about 45–54 millimetres (1.8–2.1 in).These ammonites have a planulate shell with a quadrate whorl section, bearing strong radial ribs ending in ventro-lateral tubercles. The venter is tabulate with a strong serrated keel.
These ammonites lived in the Jurassic from Sinemurian to Toarcian [2] (age range: 196.5 to 182.0 million years ago). Fossils of this genus can be found in Argentina, Austria, Canada, Chile, China, France, Germany, Hungary, Italy, Morocco, Portugal, Slovakia, Spain, Tunisia, Turkey and United States.
These ammonites have a strongly ribbed shell and ammonitic suture. Early whorls are coronate, which later become round, then oval in section. Primary ribs may have swellings (bullae) at the umbilicus or are without.
A rare heteromorph ammonite fossil from the south of France. The species is Crioceratites nolani and the spines have been partially restored to show how it might have appeared in life. Crioceratites is an ammonite genus from the Early Cretaceous belonging to the Ancyloceratoidea.