The terrifying "face hugger" turned out to be a "sea fairy"

There is a strange group of animals in the ocean. They radically change their body shapes and break through our understanding of life, but they conservatively never leave the ocean. Some of them twist their limbs like strange species, while others are as graceful as flowers. They are the phylum Echinodermata. They are also often used as the prototype of monsters in various movies, such as the scary face hugger in the famous sci-fi horror movie "Alien", the prototype of which is the protagonist of this article - crinoids.

Ecological map of passive drift of crinoids

Sea lilies belong to the class Crinoides in the phylum Echinodermata. Their bodies are generally composed of three parts: roots, stems, and crowns (calyx and arms). They are named because of their appearance similar to "lilies". In the long history of 500 million years since the beginning of the Paleozoic Era, they have been constantly multiplying in the sea. However, they are not as ferocious and fast-moving as face huggers, and they will not parasitize their eggs in the human body.

The most primitive crinoids appeared in the Cambrian strata in eastern Guizhou. They were a simple benthic sessile "primitive crinoids". In the Ordovician and Silurian periods, crinoids gradually prospered, but the fossils found were mostly scattered preserved stems, stem nodes, arms and pinnae fragments. From the Devonian to the Carboniferous period, crinoids were already quite prosperous, and sometimes finger-like crinoid stems were found. They often coexisted with other organisms in the shallow seabed, such as corals, bryozoans, brachiopods, etc. The common sea lily fossils in the Permian period were mainly scattered fragments of sea lily stems or arms, preserved in limestone and siliceous rocks; in the middle and late Triassic strata in Guanling, Guizhou, about 240 million years ago, a large number of well-preserved "incisional sea lilies" with long stems can be found; since the Jurassic, Cretaceous and Cenozoic, the sea water in Asia has receded except for the Himalayas and Taiwan, so only some sea lilies with or without stems have been found in Europe, the United States and western my country.

Chinese Crinoids

Crown of Crinoidea guanlingensis

The preservation form of fossils can be used to roughly determine the age of the strata and accurately determine the sedimentary environment: if a relatively complete calyx or arm is found, it is a "low-energy zone" sedimentary environment in a bay with relatively calm seawater or in deeper water; if only a scattered accumulation of debris of many stems, arms, and feathers is found, it is a "high-energy zone" sedimentary environment in shallow coastal waters with turbulent seawater. From this, it can be seen that crinoids tend to develop from shallow sea environments to deep water environments, and from stem-bearing species to stemless species.

The low energy band environment is completely preserved

High energy band environment discrete preservation

Many people once thought that sea lilies were like lilies, with roots and stems at the bottom and the calyx and arms of the crown at the top, growing fixed on the seabed. However, in the brown-red siltstone layer of the Middle Silurian Period in Baoshan, Yunnan, the "Shidian cup sea lily" was discovered with its crown facing downward, hanging upside down by its own floating organs.

Shidian cup crinoid with air sac

With the accumulation of fossil data and unremitting research, people gradually discovered that among the crinoid animal communities, there are both benthic sessiles and large communities with floating and wandering ecology, such as the "Shidian Cup Crinoids" and the Triassic "Crinoids of the Cretaceous" discovered in Guanling, Guizhou, which are typical of the two types of crinoid communities with floating ecology. The only difference is that the former has its own floating organs, while the latter is attached to external driftwood on the sea surface.

Due to the stirring of waves and currents, complete sea lily fossils are usually rare. However, since the Cretaceous Sea Lily lives in the closed and calm waters of Guanling, Guizhou, its output scale is particularly large and its overall preservation is particularly perfect. Complete group pieces can even be pieced together into a huge fossil wall, which is quite spectacular. Some of them coexist with ichthyosaur and sea dragon fossils, called "dragon belt flowers", which have extremely high research, appreciation and collection value.

Symbiosis between crinoids and ichthyosaurs

In the sea where the law of the jungle prevails, most sea lilies today have given up their easily broken long stems in order to survive. They are able to move freely and drift around. They have beautiful colors that can change color with the environment. They have gradually become a prosperous family in the modern sea lily family and are called "sea fairies" or "sea feather stars."

The above is what we shared in this issue. See you next time if you are interested.

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