Sponge reefs are reefs formed by Hexactinellid sponges, which have a skeleton made of silica, and are often referred to as glass sponges.Such reefs are now very rare, and found only on the western Canadian continental shelf. Although common in the late Jurassic period, sponge reefs were believed to have gone extinct during or shortly after the Cretaceous period, until the …

Oreaster reticulatus, commonly known as the red cushion sea star or the West Indian sea star, is a species of marine invertebrate, a starfish in the family Oreasteridae.It is found in shallow water in the western Atlantic Ocean and the Caribbean Sea.