Ophiothrix

Evolution

The fossil record of brittle stars can be traced back around 500 million years to Early Ordovician period. Despite the fact there have been a considerable number of fossils reported from Paleozoic, Mesozoic and Cenozoic periods, a startlingly little amount is known about the evolutionary history of the group. Paleozoic ophiuroids bear an uncanny resemblance to the modern relatives with respect to ambulacral plate pairs which have been fused firmly into their vertebrae and ambulacral groove which their ventral arm plates cover. They also have the presence of ventrally lateral arm plates.