Neocrinus decorus (Isocrinidae)
Grand Bahama Island, 420m
(Photo copyright © 1997 Charles Messing)
For many years it was thought that living crinoids were quite rare. However the Challenger expedition (1827 - 1876) dredged up as many as 10 000 unstalked individuals in a single haul. In fact crinoids are widely established particularly between latitudes 51 degrees south and 81 degrees north.
They exclusively belong to the sub-order Articulata and one such example is Neocrinus (pictured right). Five distinct groups of articulates survive in modern seas all of which number at least 100 genera and probably more than 1000 species. Unlike their Palaeozoic relatives, modern day crinoids are more frequently found stem-less. Even Pentacrinus (with stem) is known to break away from the stem in adult life to become a free-swimmer. The retained cluster of cirri suggest that modern day crinoids may have re-anchored themselves to the substrate or some object at some time.
Living crinoids are gregarious, tending to live in groups of immense populations in clear marine waters. Perhaps their gregarious habit helps to explain why fossil crinoid localities are sporadic.