"Corals are fossils"
In case o the red corals it is skeleton parts of a noble coral. They are animals, as otherwise all corals. Usually the body has a cylindrical shape and is supported in the ground with some lamellar little feet. Higher orifice (esophagus) is surrounded by tentacles. To protect its soft body most corals surround themselves with an external skeleton that it is obtained from the secretion of calcium carbonate. Reefs are constructed of many coral colonies.