Starfish (Petraster?) & Edrioasteroid Plate - Ordovician

This is a fossil echinoderm slab from the Ordovician aged Tioririne Formation near Blekus, Morocco. It contains three fossil starfishs, probably of the genus Petraster as well as about a dozen fossil Edrioasteroids. The rock is about 14x4.8" and the largest starfish is 2.5" wide. The orange coloration of the fossils is due to oxidization of iron pyrite which originally replaced the fossils.

Edrioasteroids are an extinct class of echinoderms that lived from the Ediacaran until the Permian, about 300 million years ago. The living animal would have resembled a pentamerously symmetrical disc or cushion.