Perisphinctoidea

Perisphinctoidea, formerly Perisphinctaceae, is a superfamily of Middle Jurassic (Bajocian) to Lower Cretaceous (Barremian) ammonites, commonly with evolute shells with strong ribbing that typically divides about mid flank before crossing the venter. Some 16 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)