Cleistosphinctes

{{italic title}}

{{Taxobox

|name = Cleistosphinctes

|fossil_range = {{fossil range|Bajocian|ref=}}

|regnum = Animalia

|phylum = Mollusca

|classis = Cephalopoda

|subclassis = Ammonoidea

|ordo = Ammonitida

|superfamilia = Perisphinctaceae

|familia = Perisphinctidae

|genus = Cleistosphinctes

}}

Cleistosphinctes is an extinct cephalopod genus from the ammonite order that lived during the Middle Jurassic.{{cite journal|last=Sepkoski |first=Jack |title=A compendium of fossil marine animal genera (Cephalopoda entry) | journal=Bulletins of American Paleontology |volume=363 |pages=1–560 | year=2002 | url=http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=231&rank=class |accessdate=2017-10-18 |url-status=dead | archiveurl=https://web.archive.org/web/20080507014300/http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=231&rank=class | archivedate=2008-05-07 }}

Cleistosphinctes, named by Arkell, 1953, and included in the family Perisphinctidae and superfamily Perisphinctaceae, is small, compressed, evolute, with long secondary ribs and very large asymmetric spatulate lappets that embrace the sides of the preceding whorl.