Perisphinctus Fossils: Spirals from the Jurassic Seas

Perisphinctus Ammonite Fossil

The fossilized shells of Perisphinctus ammonites are among the most striking relics of the Jurassic Period, roughly 165 to 155 million years ago. These beautiful, ribbed shells once housed fast-moving marine predators that lived in the warm, shallow seas covering much of what is now Europe, Madagascar and parts of India. Perisphinctus belonged to the broader Ammonoidea family, extinct relatives of modern squids and cuttlefish. They flourished during the Middle to Late Jurassic before disappearing near the end of that era.

Artist impression of a Perisphinctus Ammonite

In life, Perisphinctus would have had a tightly coiled, disc-shaped shell with bold ribs running across its surface, housing a soft-bodied creature with tentacles extending from the shell’s opening. These ammonites moved by jet propulsion, expelling water through a siphon to dart through the sea much like modern squids do. Their chambered shells helped them control buoyancy, allowing them to hover or dive with ease while hunting small crustaceans and plankton. The rhythmic pattern of their ribs wasn’t just decorative, it gave the shell strength against pressure and predators, adding to their survival advantage in the Jurassic seas.

How does the Perisphinctus compare to our other Ammonites?

	Perisphinctus	Cleoniceras	Dactylioceras
Geological Age	Middle to Late Jurassic (165–155 million years ago)	Early Cretaceous (120 million years ago)	Early Jurassic (180 million years ago)
Shell Shape	Large, flat spiral with strong evenly spaced ribs	Smooth, rounded shell with gentle curves	Tight, compact coils with bold, pronounced ribs
Suture Pattern	Complex and deeply frilled	Very intricate and delicate	Moderately complex, wavy sutures
Typical Size	Up to 25–30 cm in diameter	Around 10–15 cm	Usually 10–20 cm
Fossil Locations	Europe, Madagascar, India	Madagascar, Europe	Europe, especially England and Germany

When compared to their relatives, Perisphinctus stood out for its large size and bold shell sculpture. Cleoniceras, from the Early Cretaceous, evolved later and displayed smoother, more elegant whorls with delicate patterns — almost refined in appearance. Dactylioceras, on the other hand, from the Early Jurassic, had tighter coils and coarser ribs, giving it a more compact and rugged look. Together, they show the incredible diversity of ammonite design through time.