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 it eradicates the bulk of the starfish in a given area, human divers can move in and remove the survivors. Field trials of the robot have begun in Moreton Bay in Brisbane to refine its navigation system, according to Queensland University of Technology researcher Matthew Dunbabin. There are no crown-of-thorns starfish in Moreton Bay, but when the navigation has been refined, the robot will be used on the reef. 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