{{Short description|Genus of molluscs (fossil)}}
{{Automatic taxobox | fossil_range = Hauterivian<br/>~{{fossil range|133|130}} | image = Acanthodiscus radiatus.png | image_caption = Acanthodiscus radiatus | taxon = Acanthodiscus | authority = Uhlig 1905 | subdivision_ranks = Species | subdivision = * ''A. magnificus'' {{small|Imlay 1938}} *'' A. marocanus'' * ''A. octagonus'' * ''A. ottmeri'' * ''A. radiatus'' {{small|Bruguiére 1792}} * ''A. rollieri'' * ''A. schmidtii'' * ''A. subradiatus'' {{small|Uhlig 1910}} | type_species = '''''Acanthodiscus radiatus''''' }}
'''''Acanthodiscus''''' is an extinct ammonoid cephalopod genus from the order Ammonitida and included in the persphinctacean family Berriasellidae. The type species, named by Bruguière, 1792, is ''Acanthodiscus radiatus''.<ref name=FW>[https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=14510 ''Acanthodiscus''] at Fossilworks.org</ref>
== Description == The shell of ''Acanthodiscus'' (''A. radiatus'') is of modest size, slightly more than {{convert|14|cm|in}} in diameter, coiled with the outer whorl covering about a third of the next inner whorl. The lower (2/3) flanks bear strong, wide spaced, radial ribs with large nodes at either end, and become weaker on the mature body chamber. Outer flanks (approx. 1/3) slope toward a narrow, flat to concave venter lined on either side by a series of smaller nodes. the mature whorl section is higher than wide.
== Biostratigraphic significance == ''Acanthodiscus'' is found in shallow water sediments in both the Tethyan and Boreal realms where it is used as an index fossil. In fact, the International Commission on Stratigraphy (ICS) has assigned the First Appearance Datum of ''Acanthodiscus radiatus'', the first species of the genus, as the defining biological marker for the start of the Hauterivian stage of the Cretaceous, ~132.9 million years ago.
== Species == * ''A. radiatus''; type species * ''A. marocanus'' * ''A. octagonus'' * ''A. ottmeri'' * ''A. rollieri'' * ''A. schmidtii''; Found on the Antarctic Peninsula * ''A. subradiatus''
== Distribution == ''Acanthodiscus'' fossils can be found in the Agrio Formation of the Neuquén Basin, Argentina. Also in the Macanal Formation of the Eastern Ranges of the Colombian Andes, fossils of ''Acanthodiscus'' have been found.<ref name=Piraquive_p204>Piraquive ''et al.'', 2011, p.204</ref>
Other occurrences of the genus are in:<ref name=FW/> * Abundancia Formation, Chile * Guchuochun Formation, China * Kaliste Formation, the Czech Republic * France * Giumal Sandstone Formation, India * Chia Gara Formation, Iraq * Sardinia, Italy * Sabinal Formation and Barril Viejo Shale Member, Mexico * Myrtle Formation, Oregon, United States
== References == {{Reflist|3}}
=== Bibliography === * {{citation |last=Piraquive |first=Alejandro |last2=Díaz |first2=Juan Sebastián |last3=Cuéllar |first3=Tomas |last4=Pardo |first4=Germán |last5=Kammer |first5=Andreas |year=2011 |title=Reactivación Neógena de estructuras de rift del Cretácico Temprano asociadas con la Falla de Chámeza, Pajarito, Boyacá (Colombia): evidencias tectónicas y bioestratigráficas |url=http://www.bdigital.unal.edu.co/24942/1/22167-87412-2-PB.pdf |journal=Geología Colombiana |volume=36 |pages=197–216 |accessdate=2017-08-04 |archive-date=2017-03-30 |archive-url=https://web.archive.org/web/20170330091900/http://www.bdigital.unal.edu.co/24942/1/22167-87412-2-PB.pdf |url-status=dead }}
== External links == * [https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=14510 Acanthodiscus-Paleodb] * [http://www.ammonites.fr/Fiches/0548.htm ''Acanthodiscus radiatus''] {{Webarchive|url=https://web.archive.org/web/20150413001423/http://www.ammonites.fr/Fiches/0548.htm |date=2015-04-13 }} in French * T. Birkelund, et al.: Cretaceous Stage Boundaries - Proposals. Bulletin of the Geological Society of Denmark, vol. 33 1984 [http://2dgf.dk/xpdf/bull33-01-02-3-20.pdf]
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Category:Ammonitida genera Category:Prehistoric cephalopod genera Category:Index fossils Category:Hauterivian life Category:Ammonites of Asia Category:Cretaceous China Category:Fossils of China Category:Cretaceous India Category:Fossils of India Category:Fossils of Iraq Category:Ammonites of Europe Category:Fossils of the Czech Republic Category:Cretaceous France Category:Fossils of France Category:Cretaceous Italy Category:Fossils of Italy Category:Ammonites of North America Category:Cretaceous Mexico Category:Fossils of Mexico Category:Fossils of the United States Category:Ammonites of South America Category:Cretaceous Argentina Category:Fossils of Argentina Category:Cretaceous Chile Category:Fossils of Chile Category:Cretaceous Colombia Category:Fossils of Colombia Category:Extinct animals of Antarctica Category:Fossil taxa described in 1792 Category:Fossil taxa described in 1905 Category:Perisphinctoidea