Starfish first appeared in the fossil record in the Cambrian. The first known asterozoans were the Somasteroidea, which exhibit characteristics of both groups. Starfish are infrequently found as fossils, possibly because their hard skeletal components separate as the animal decays. Despite this, there are a few places where accumulations of complete skeletal structures occur, fossilized in place in Lagerstätten — so-called "starfish beds". By the late Paleozoic, the crinoids and blastoids were the predominant echinoderms, and some limestones from this period are made almost entirely from fragments from these groups. In the two major extinction events that occurred during the late
Crown-of-thorns starfish Crown-of-thorns starfish The crown-of-thorns starfish, "Acanthaster planci", is a large starfish that preys upon hard, or stony, coral polyps (Scleractinia). The crown-of-thorns starfish receives its name from venomous thorn-like spines that cover its upper surface, resembling the biblical crown of thorns. It is one of the largest starfish in the world. "A. planci" has a very wide Indo-Pacific distribution. It is perhaps most common in Australia, but can occur at tropical and subtropical latitudes from the Red Sea and the east African coast across the Indian Ocean, and across the Pacific Ocean to the west coast of Central America. It