page_title: List of ammonite genera
section_title: A
hierarchical_section_title: List of ammonite genera / A
caption_attribution_description: English: Photograph of the ammonite Asteroceras obtusum from the Jurassic Lower Lias Formation, Obtusum Zone. Locality - Lyme Regis, Dorset, England. Complete calcified specimen, measuring 11.5 cm (4.5") in diameter, in limestone matrix.
context_page_description: This list of ammonites is a comprehensive listing of genera that are included in the subclass †Ammonoidea, excluding purely vernacular terms. The list includes genera that are commonly accepted as valid, as well those that may be invalid or doubtful, or were not formally published, as well as junior synonyms of more established names, and genera that are no longer considered ammonites.
caption: Asteroceras, a Jurassic ammonite from England.
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