Perisphinctoidea, formerly Perisphinctaceae, is a superfamily of Middle Jurassic

Jurassic

The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 (Bajocian) to Lower Cretaceous (Barremian) ammonites

Ammonitina

The Ammonitina comprises a diverse suborder of ammonoid cephalopods that lived during the Jurassic and Cretaceous periods of the Mesozoic Era. They are excellent index fossils, and it is often possible to link the rock layer in which they are found to specific geological time periods.The shells of...

, commonly with evolute shells with strong ribbing that typically divides about mid flank before crossing the venter.

Classification

Some 18 families have been recognized in the Perisphinctoidea. The following is based on Donovan et al. 1981 with modification from the Treatise on Invertebrate Paleontology, Part L (1957)

Treatise on Invertebrate Paleontology

The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...

• Perisphinctidae
  Perisphinctidae
  Perisphinctidae is a family of Middle and Upper Jurassic discoidal ammonites in the order Ammonitida. They have a shell morphology that is mostly evolute, typically with biplicate, simple, or triplicate ribbing...
  
  : Middle and Upper Jurassic root stock, derived from the Stephanoceratidae
  Stephanoceratidae
  Sephanoceratidae is a family of planulate and coronate ammonites within the Stephanocerataceae. Shells are evolute so that all whorls are exposed and have strong ribbing that bifurcates, that is splits in two, on the flanks. Many have tubercles at the point of bifurcation...
  
  

(Middle Jurassic direct derivatives of the Perisphinctidae)

• Morphiceratidae
• Tulitidae
• Reineckeiidae
• Pachyceratidae
  Pachyceratidae
  Pachyceratidae is a family of Perisphinctacean ammonites from the upper Middle - and lower Upper Jurassic. Genera within the Pachyceratidae have shells that are in general moderately involte but with most of the inner whorls exposed; whorl sections subquadrate to subtrapezoidal, with rounded...
  
  
• Aspodoceratidae

(early Upper Jurassic (Oxfordian) derivatives of Perisphinctidae)

• Aulacostephanidae
• Ataxioceratidae

(mid Upper Jurassic (Kimmeridgian) derivatives of the Ataxioceratidae)

• Dorsoplanitidae
• Virgatitidae

(late Upper Jurassic (Tithonian) derivatives of Perisphinctidae)

• Simoceratidae
• Himalayitidae
• Olcostephanidae
• Holcodiscidae (indirect, from Olcostaphanidae)

(Lower Cretaceous Perisphinctoidea (Berriasan - Hauterivien)

• Polytichitidae [=Craspeditidae] (derived from Dorsoplanitidae)
• Berriasellidae
  Berriasellidae
  Berriasellinae is a subfamily of very late Jurassic and very early Cretaceous perisphinctoid ammonites in the family Neocomitidae. Berriasellinae comprises generally compressed, evolute genera, typically with furcated ribbing, and in some a smooth ventral band or groove. Berriasellinae are...
  
   (derived from Ataxioceratidae)
• Neocomitidae(derived from Berriasellidae)
• Oosterellidae (Hauterivian derivative of the Neocomitidae)