<Dd> The largest sea urchin is the species Sperosoma giganteum from the deep northwest Pacific Ocean, which can reach a shell width of about 30 cm (12 in). Another deep sea species Hygrosoma hoplacantha is only slightly smaller . The largest species found along the North America coast is the Pacific red sea urchin (Mesocentrotus franciscanus) where the shell can reach 19 cm (7.5 in). If the spines enter into count, the biggest species may be a Diadematidae like Diadema setosum, with a test up to 10 cm (3.9 in) only, but its spines can reach up to 30 cm (12 in) in length . </Dd> <Ul> <Li> Sea cucumbers (Holothuroidea) </Li> </Ul> <Li> Sea cucumbers (Holothuroidea) </Li> <Dl> <Dd> The bulkiest species of sea cucumber are Stichopus variegatus and Thelenota anax, weighing several pounds, being about 21 cm (8.3 in) in diameter, and reaching a length of 1 m (3.3 ft) when fully extended . Synapta maculata can reach an extended length of 3 m (9.8 ft), but is extremely slender (3 - 5cm) and weigh much less than Stichopodids . </Dd> </Dl>

What was the biggest living thing on earth