Crinoids
There is an animal that lives on the seabed and is as beautiful as a lily. People call it "Crinoids". Crinoids are marine echinoderms. They are not plants like land lilies and cannot live without sea water. However, its beautiful appearance resembles that of the lily, which is why people gave it a plant name.
Crinoids are the oldest species of echinoderms and there are more than 620 species of crinoids worldwide. Often divided into two categories: sessile crinoids and sessile crinoids. The stemmed crinoid is attached to the deep sea floor with its long stem, where there is no wind or waves and does not require strong anchorages. The stem has a receptacle that contains all of its internal organs. The mouth and anus of crinoids open upward, which is different from other echinoderms. Its slender arms extend from the receptacle. The arms are made up of branches and canmoving sideways like feathers. The arms face the current like a windmill, catching small animals in the sea for food. Sessile crinoids do not have long stems, but have several small roots or arms. The mouth and digestive tract are also located in the center of the torus-shaped structure, which may float or be attached to the seafloor. While floating, tighten the wrist, and when stopping, use the wrist to secure it on the seabed or rocks on the seabed. The number of arms varies depending on the type of crinoid. The smallest number is only 2 and the highest number is over 200. As there are small branches on both sides of each arm, they are shaped like feathers. Each wrist has a body band-like groove with branches leading to the rami on both sides. On both sides of the groove there are tentacle-shaped tube feet with mucus secretion. Crinoids aretypical filter feeders. When feeding, they raise their wrists high. Plankton or other suspended organic matter is captured by the tube feet and sent into the walking furrow. In ancient times, there were many types of crinoids, with more than 5,000 fossil species, so they were of great geological importance. Some limestone formations are composed entirely of crinoid fossils.
In some villages and towns in northeast Guizhou, roads and steps are paved with local materials and stones. The stones are collected from the nearby mountains. Over time, the surfaces of these stones became very smooth. , if you look closely at these smooth surfaces, you will find beautiful patterns, small circles one by one, which are completely different from the surrounding stones. If you're lucky, you'll see bright red five-pointed stars. They are crinoids.fossils.
Most crinoids from the Paleozoic and Mesozoic eras inhabit shallow seabeds. Crinoids first appeared at the start of the Ordovician dynasty around 480 million years ago. During the long geological history, they have flourished several times (Carboniferous and Permian). The number of species in its genus accounts for a third of the total number of different types of echinoderms, and more than 700 species still survive in the modern ocean.
After the death of the crinoids, these calcareous stems and calyxes are easily preserved and become fossils. Due to seawater disturbance, these stems and calyxes are still scattered and preserved, losing their beautiful lily-like appearance. . But if they happen to live on a particularly calm seabed, after their death, their postures will be entirely preserved and will become fossils. Because this environment is relatively harsh, Thereforeent, these fossils are very precious. They not only provide important evidence for the study of ancient environments in historical geological periods, but also gradually become treasures for fossil collectors and are even displayed as handicrafts.
In marine sedimentary rocks formed during the period when crinoids flourished, crinoid fossils are very abundant and may even become the main component of building limestone, but most of what is seen are scattered stem rings. The main component of crinoid fossils is single-crystal calcite, which is usually white, sometimes mixed with ferric iron ions, giving it a bright red color. It is very beautiful against the surrounding blue-gray rock. Limestone containing very rich crinoid fossils is called crinoid stem limestone by geologists. Some residents locaux extracted these rocks and crushed them to make various handicrafts, euphemistically called “lily jade”.
Crinoids spend their entire lives rooted to the bottom of the sea and cannot walk. They are often ravaged by fish, some have their stems torn off, others have their flowers eaten and end tragically. In a sea where the strong prey on the weak and competition is fierce, there have been batches of crinoids whose stems have been torn off, leaving only the flowers, and which have survived the catastrophe. Because after all, they are not plants, the stems are not that essential in their life. This type of stemless crinoid is colorful, wandering and drifting, and is known as the "Sea Fairy." Biologists have given it another nickname: “Feather Star.” Feather stars contain toxins and many fish do not dare to touch them. But there are still fish that do not haveafraid of toxins and who are ruthless and vicious towards them. To survive, they had no choice but to hide in rock crevices during the day; It was only at night that they came out of their holes in groups and danced. Their method of capturing prey is always the same: the wrist branches face the water current and spread flat, like a spider insect net, waiting for the rabbit to arrive, waiting for the arrival food.
Because feather stars can move freely and their bodies can change color depending on the environment, they have become a popular member of the crinoid family, with more than 480 species in existence . They like to settle in coral reefs because the water is warm, there are many life forms and it is easy to find food. Stalked crinoids have poor adaptability and cannot protect themselves effectively,so their numbers are becoming increasingly rare, with only around 70 species existing. Maybe in a few hundred years they will eat all the fish and disappear from the sea forever!