Sea urchin
Sea urchins or urchins () are typically spiny, globular animals, echinoderms in the class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal to . Their tests (hard shells) are round and spiny, typically from across. Sea urchins move slowly, crawling with their tube feet, and sometimes pushing themselves with their spines. They feed primarily on algae but also eat slow-moving or sessile animals. Their predators include sea otters, starfish, wolf eels, and triggerfish.
Plesiocidaris
Plesiocidaris durandi is an extinct species of sea urchins. Including its spines, the creature was 13 cm (5 in) wide. Its remains have been found in Drâ el-Ahmar, near the Atlas Mountains in Oran, Algeria. A Commander Durand found the fossils there in 1870 and sent them to French paleontologists. The exact location of the find was not noted and has not been rediscovered since. The species name, "durandi", refers to Commander Durand. Most "Plesiocidaris" fossils still have the spines attached, indicating they lived in calm water; the spines of dead sea urchins are easily detached by wave currents.