Perischoechinoidea

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Lanz of recent sea urchins

The Perischoechinoidea mainly include primitive and now extinct sea urchin species. The exoskeleton consists of many partially irregular rows of plates.

All species living today belong to the order Cidaroida that in the two families lance urchins ( Chidaridae ) and Psychocidaridae is divided.

Extinct taxa are eg Aulechinus and Bothriocodaris from the Ordovician 450 million years ago, the oldest known sea urchins. Archaeocidaris lived from Carboniferous to Permian, Jurassic and Hemicidaris Plegiocidaris in the Jurassic and the Cretaceous. Only the order Cidaroida survived the mass extinction at the end of the Cretaceous.