Fossil - Ammonites - Perisphinctes sp.

White Spined Ammonites belong to the Perisphinctes genus which contains no less than 14 different species. This genus of ammonites has a cosmopolitan distribution being particularly widespread in warm-temperate waters worldwide. Shells belonging to this genus have been found in the Jurassic of Antarctica, Argentina, Chile, Cuba, Egypt, Ethiopia, France, Germany, Hungary, India, Iran, Italy, Japan, Madagascar, Poland, Portugal, Russia, Saudi Arabia, Spain, Switzerland, the United Kingdom and Yemen. 

Perisphinctes sp. ammonites are an extremely import index taxa for identifying Late Jurassic strata in the fossil record.  It has been suggested that they lived in the inner part of the continental shelf and shelf seas interior. It has been suggested that food web collapse and ocean acidification resulted in their extinction. In that, ocean acidification towards the end of the Cretaceous likely dissolved the shells of their microscopic young, which floated on the ocean's surface early in their life-cycle. Whilst devastation of plankton species during this period impacted on their primary food source.