Article number F0077
|Origin (country)||Holzmaden, Germany|
|Dimension (hxwxd)||142.0 x 82.0 x 3.5 cm|
Crinoids are marine animals belonging to the Echinodermata. They are related to the starfish, sea urchins, brittle stars and sea cucumbers. They first appeared on Earth in the Ordovician, around 480 million years ago, and quickly evolved into one of the most dominant species at that time. There are two types of crinoids, the free-swimming ones that are called feather stars because of their appearance, and the crinoids that are attached to the bottom with a stem, which are understandably called sea lilies because they look like flowers. They use this "flower" to filter food particles from the water. While some members of the Echinodermata can reproduce by cloning, crinoids cannot. They reproduce by means of sperm and eggs making them rather vulnerable. But on the other hand, they are able to regenerate body parts that they lose, for example by a predatory fish. This might explain the success of the species in geological history. Although they used to be present in large numbers in the world's oceans, crinoid fossils are quite rare. This is because they almost always fall apart after dying. Therefore, we often only find pieces of the "flower" or parts of their very typical pentagonal body. About this piece Seirocrinus subangularis More than 180 million years ago, in the Toarcian, southern Germany was covered by a tropical sea. The conditions back then were similar to those in the Caribbean Sea today; with a large variety of marine fauna, but not at the bottom. There, the oxygen conditions were so poor that only a few animals could survive. The result was that most of the animals that died were not eaten by bottom-dwelling organisms and did not decay because of the lack of oxygen. Add to this the fact that there was hardly any current in the inland sea and that the sediment was very fine, and you have the ideal conditions for fossilisation: the skeletons remain intact and, because of the cover of very fine sediment, many details are preserved. When Johannes Bauhin, a medical doctor, found a fossil sea lily in the rocks near Holzmaden in 1598, he thought it must have been either a huge flower or a head of medusa. In any case, for him it was "the" proof of the Biblical Flood. In one respect he was right, they had been carried away by the current. Normally, sea lilies cannot live in a sea where the bottom is deprived of oxygen. But Seirocrinus subangularis, the scientific name for this fossil sea lily, had a very special trait: it did not attach its stalk to the inhospitable sea floor, but instead used driftwood and was therefore not affected by the lack of oxygen. This truly magnificent specimen has something extra: it is pyritised. The bacteria in the oxygen-free soil that live off the organic components of the sea lily have caused the original calcium skeleton to slowly but surely turn into pyrite. And because of the fine graining of the pyrite, even the finest details have been preserved.