LATE ORDOVICIAN PERIOD to PRESENT: 450 million years ago to present day
Sea urchins are ECHINOIDS and are members of the echinoderm family with their first fossils dating back to the Late Ordovician. They survive today and are a diverse group of organisms. Sea urchins possess spines protruding out from a central ball-shaped body called a TEST. When they die, the spines usually fall off the test and all that remains is the central body. In some cases, echinoid fossils are found in layered rock that show the spines articulated and spread out from the test. Most fossils found of sea urchins are isolated spines or just the tests with no spines.
Sea urchins live on the bottom of soft ocean floors. They move about the bottom by the use of small tube feet. Their diet consists of various living and decaying plant and animal matter