Cleistosphinctes
Encyclopedia
Cleistosphinctes is an extinct cephalopod genus from the ammonite
order that lived during the Middle Jurassic approximately 174 to 170 million years ago.
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.
Ammonitida
The Ammonitida is an order of more highly evolved ammonoid cephalopods from the Jurassic and Cretaceous time periods, commonly with intricate ammonitic sutures....
order that lived during the Middle Jurassic approximately 174 to 170 million years ago.
Cleistosphinctes, named by Arkell, 1953, and included in the family Perisphinctidae and superfamily Perisphinctaceae
Perisphinctaceae
Perisphinctoidea, formerly Perisphinctaceae, is a superfamily of Middle Jurassic to Lower Cretaceous ammonites, commonly with evolute shells with strong ribbing that typically divides about mid flank before crossing the venter....
, is small, compressed, evolute, with long secondary ribs and very large asymmetric spatulate lappets that embrace the sides of the preceding whorl.