These specimens date back to the Mid-Jurassic - 150 to 160 million years ago

The ammonite Perisphinctes is a genus of extinct marine cephalopods that belong to the subclass Ammonoidea. These organisms lived during the Jurassic period, approximately 150 to 160 million years ago. The genus is notable for its distinctive, coiled shell and intricate suture patterns, which provide valuable information for paleontologists studying the evolutionary history and paleoecology of ammonites.

Perisphinctes, like other ammonites, possessed a planispiral shell, meaning the shell coiled in a single plane. This coiling produced a spiral structure with numerous whorls, which are the complete 360-degree turns of the shell. The shells of Perisphinctes typically exhibit strong ribbing, with ribs extending from the inner whorls to the outer edge, providing structural support and potentially aiding in hydrodynamics.

One of the defining features of Perisphinctes is its complex suture pattern. Sutures are the lines where the septa, the walls separating the internal chambers of the shell, meet the outer shell wall. In Perisphinctes, these sutures are highly intricate and frilled, a characteristic that is often used to distinguish between different ammonite species and genera. The suture patterns in Perisphinctes are typically ammonitic, meaning they have highly convoluted and branching lobes and saddles.

Like all ammonites, Perisphinctes went extinct at the end of the Cretaceous period, around 66 million years ago, during the Cretaceous-Paleogene extinction event. This mass extinction event wiped out nearly 75% of Earth's species, including all non-avian dinosaurs and a vast majority of marine organisms. The precise causes of the K-Pg extinction are still debated, but it is commonly attributed to a combination of volcanic activity, climate change, and the impact of a large asteroid.

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