Perisphinctidae

The Perisphictide is a family of middle and upper Jurassic ammonites (order Ammonitida) that forms the root stock of the Perisphictaceae, having given rise to the remaining associated families. It is thought to have its origin in the Stephaniceratidae and includes some five subfamilies, as shown.

Perisphinctid genera produced shells that are typically evolute, closely coiled with all whorls exposed, but subinvolute in some with whorls strongly overlapping. Whorls are commonly ribbed, with ribs variable in thickness and spacing but typically straight.