{{Short description|Genus of molluscs (fossil)}} {{Italic title}} {{Automatic taxobox | fossil_range = {{fossil range|Carnian|Rhaetian|ref=<ref name="Sepkoski Ceph">{{cite web | last = Sepkoski| first = Jack| title= Sepkoski's Online Genus Database|authorlink =| year = 2002| url = http://strata.geology.wisc.edu/jack/showgenera.php?taxon=231&rank=class| accessdate = 2014-05-28 }}</ref>}} | image = Arcestes.jpg | image_caption = ''A. intuslabiatus'' and ''A. binacostomus'' | taxon = Arcestes | authority = Suess, 1865<ref name="IRMNG-Arcestes">{{cite web |title=''Arcestes'' Suess, 1865 † |url=https://www.irmng.org/aphia.php?p=taxdetails&id=1275747 |website=Interim Register of Marine and Nonmarine Genera |access-date=20 March 2025 |archive-url=https://web.archive.org/web/20250215225604/https://www.irmng.org/aphia.php?p=taxdetails&id=1275747 |archive-date=15 February 2025 |language=en |url-status=live}}</ref> | subdivision_ranks = Species | subdivision_ref = <ref name="paleodb">[https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=14031 Paleobiology Database - Arcestes]. 2014-05-29.</ref> | subdivision = * ''A. (Pararcestes)'' * ''A. andersoni'' † Hyatt and Smith 1905 * ''A. intuslabiatus'' † Mojsisovics 1873 * ''A. megaphyllus'' † Beyrich 1864 * ''A. priscus'' † Waagen 1879 * ''A. syngonus'' † Mojsisovics 1873 }}
'''''Arcestes''''' is a genus of extinct ceratitid ammonites found in Triassic-aged marine strata.
==Description== Their shells were broad and rounded, giving them an almost spherical appearance. Unlike many other ammonites, the shells of ''Arcestes'' lack keels that would otherwise stabilize them while swimming. Because of this, some paleontologists have suggested that they were bottom-dwelling crawlers.
The shell of ''Arcestes'' is globular or subglobular with periodic narrow transverse constrictions in internal molds due to periodic internal transverse ridges (varices) in the shell. The suture is ammonitic with complexly subdivided elements. The ventral lobe is subdivided by a low median saddle. Lateral lobes and saddles have generally triangular outlines but are deeply embayed by strong projections forming tree-like patterns. They form a series diminishing in size and complexity in a rather straight line going from the venter to the umbilicus in the middle of the shell.
==Distribution== Fossils of ''Arcestes'' are found in Mid to Upper Triassic marine strata throughout the world, including California (''A. pacificus''), Nevada (''A (Anisarcestes) mrazici'') and Austria (''A. intuslabiatus'' and ''A. binacostomus'').<ref name="paleodb"/>
==Gallery== <gallery widths="180" heights="180"> File:Arcestes 1.JPG|Museum specimen of ''Arcestes'' species File : Arcestidae - Arcestes sp.JPG|Museum specimen of ''Arcestes'' species </gallery>
== References == {{Reflist}} * Arkell et al. Mesozoic Ammonoidea. Treaatise on Invertebrate Paleontology, Part L, 1957 Geological Society of America and University of Kansas press, R.C.Moore ed. * Johnston, F.N. Trias of New Pass Nevada (New lower Karnic ammonoids); Journal of Paleontology V.15 No 5 p 447-491, Sept 1941
{{Portal|Paleontology}} {{Taxonbar|from=Q4785273}}
Category:Triassic ammonites of North America Category:Ceratitida genera Category:Late Triassic ammonites Category:Carnian genus first appearances Category:Norian genera Category:Rhaetian genus extinctions Category:Fossil taxa described in 1865 Category:Arcestidae