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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 span of Ammonites. Cretaceous Fossils Taxonomic Index for Order Ammonoitida
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 were cephalopods, that thrived in tropical seas until becoming extinct along with the dinosaurs at the end of the Mesozoic era.
Their shells had ornate ribs whose function is unknown, although some scientists have speculated that these ribs helped strengthen the animals' shells to allow them to live at greater depths where the water pressure is higher.
Dactylioceras was a widespread genus of ammonites from the Lower Jurassic period, [1] approximately 180 million years ago . [2] and Like many other ammonites, the genus Dactylioceras is extremely important in biostratigraphy, being a key index fossil for identifying their region of the Jurassic. It had a nearly cosmopolitan distribution during ...
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.
Lewesiceras is a genus of large ammonites belonging to the order Ammonitida and the family Pachydiscidae. They lived in the late Cretaceous period, in the Cenomanian and Turonian ages, which occurred 99.6-89.3 million years ago. These shelled ammonoids were nektonic, fast-moving and carnivorous.
Arnioceras is an extinct genus of large, evolute, discoidal ammonite from the Lower Jurassic. The shell is normally coiled so that all whorls are exposed. Sides bear strong sharp ribs that are straight until reaching the ventrolateral edge where they swing forward and fade. The rim (venter) is keeled and free of grooves.
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.