The "little apple" from 400 million years ago was fixed to the seabed like an anchor!

From the middle Ordovician to the late Devonian, a type of creature with a strange appearance appeared in the ocean. Their bodies were spherical or sac-shaped, covered with many irregular polygonal bone plates, with arms and legs attached to the bone plates, and their mouths, anuses, water holes, and genital openings all growing on the mouth surface surrounded by the arms and legs. This was the echinoderm Hystrix marina.

The name of the sea ringo comes from its appearance. There are many marine creatures named after their appearance. Many marine mammals are named after mammals on land that are similar in appearance, such as sea lions, walruses, seals... Echinoderms often take unusual paths in evolution and are nicknamed "extreme skin" animals. Their names are as varied as their appearance, including animals, plants, organs, and even non-living things, such as starfish, sea urchins, brittle stars, and sea lilies. The sea ringo is named because of its resemblance to the ringo. Its Latin name "Cystoids" also comes from its appearance, meaning "cystic".

Lingo means apple or red fruit, but the skin of both is very smooth, which is obviously inconsistent with the image of Hailingo covered with bone plates. Therefore, it should be closer to another famous Chaoshan fruit also called Lingo, also known as Sugar Apple.

Back to the point, sea lilies are a kind of primitive echinoderms, with many genera and species. Like early crinoids, they are composed of three parts: calyx, stem, and arms. Some species do not have a stem. The bony plates they wear are called calyx plates, which are mainly composed of hard calcium. The number and shape of calyx plates vary from species to species. They are connected to form the calyx to protect the main organs inside. The stem is located on the aboral surface and can be fixed to the seabed like an anchor. The arms are short and used to filter food in the water.

Their body size is not large, and although the organs for eating, drinking, defecating and urinating are all on the mouth, it does not appear crowded but rather very orderly: the mouth is located in the top center of the calyx, the anus is located on the side of the mouth and is covered by an anal cone formed by small bone plates, and the genital opening and water opening are located between the mouth and the anus.

Whether with or without a stem, the sea lingon adopts a benthic lifestyle. For the stemless sea lingon, the oral surface has the above functions and also plays a role in fixing the body. However, even for the sea lingon with a stem, the stem is rarely seen in three-dimensionally preserved fossils. On the one hand, the stem of the sea lingon itself is not well developed. On the other hand, since the stem does not contain important organs, it is speculated that when encountering enemies, it can sacrifice its pawns to protect its generals. After the calyx is out of danger, it can use the super regeneration ability of echinoderms to grow a stem again.

In geological history, the active period of Hailingo was not long, but it was widely distributed and has been found in North America, Europe, and Asia. In my country, it is mainly found in Yunnan and Guizhou, especially in Shidian, Baoshan, Yunnan. It is famous for the large number of Hailingo fossils discovered and their well-preserved state. It is known as the "Hometown of Hailingo in China". They originated in the Ordovician Period, flourished from the Ordovician to the Silurian Period, and became extinct in the Devonian Period. They are also an important standard fossil and an important symbol for dividing strata.