The crown of thorns starfish is often considered the most unusual member of the seastars. They are currently considered a single species Acanthaster planci but recent genetic studies suggest that it may be 4 different species.

Their thorns give protection against predators and cause dried specimens such as this one to look almost plantlike. Most specimens offered for sell are a bit larger than this specimen and are just a little too big for practical stereoscopic scanning.

Crown of thorns starfish prey on coral polyps and although they have filled an ecological role in preventing fast growing corals from crowding out slower growing forms they have in recent years been causing permanent damage to reefs already stressed by other factors.

Population explosions have led to them reaching plague proportions. These outbreaks are thought to at least partially be due to manmade factors, so human intervention has been deemed apropriate.