There is an abundant fossil record, their hard examinations made from calcite plates making it through in rocks from every duration given that then.Spines exist in some well-preserved samplings, but normally only the test continues to be. Some Jurassic and also Cretaceous Cidaroida had extremely heavy, club-shaped spinal columns. Soon, the larva sinks to the bottom and metamorphoses into a juvenile urchin in as low as one hr.