|An intact crown of the crinoid Platycrinites, with a large stem of Amphoracrinus, from the Carboniferous Limestone (340 million years old) of Hook Head, Co. Wexford.|
Often called Sea Lilies on account of their plant-like appearance, fragments of crinoids are often found as fossils and they still thrive in the seas of today. They typically have finely-branched arms used for filtering out plankton, and most fossil forms have a stem with which the crown (the arms and the cup containing most of the vital organs) are held above the sea floor.
The crinoid 'skeleton' is made of countless small calcareous plates held together with soft tissue. Following death these plates soon fall apart and so intact crinoids are rare as fossils, being preserved only under unusual circumstances.
Crinoid remains are particularly common in the Lower Carboniferous rocks of Northern Ireland, especially at certain localities in Co. Fermanagh. Fragments of stem are not uncommon in the Lower Jurassic clays along the Antrim coast but they are rather rare in the Upper Cretaceous rocks.
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