The most common fossil, many people can't even pronounce its name

Most people may not even know how to pronounce the word "䗴" (tíng), but they were once thriving creatures that were ubiquitous in the earth's oceans.

Foraminifera are tiny single-celled protists that lived in the oceans of the Paleozoic Era. They belong to the order Foraminifera of the phylum Foraminifera, which has 13 superfamilies and a wide variety of species. There are 290 families under the superfamily Endothyracea alone. They are very small, with a calcite shell that is usually only 5-10 mm long, with the smallest less than 1 mm and the largest only about 5 cm. However, some species can reach a shell length of 14 cm, making them the largest Foraminifera animals ever.

Section of a foraminifera fossil | Strekeisen / Wikimedia Commons

The family's prosperous "spindle"

The Anguidae first appeared in the Landavritian stage of the Early Silurian period, 444 to 426 million years ago. At that time, the mass extinction at the end of the Ordovician period had just ended. Rising global temperatures caused the melting of glaciers and rising sea levels. Coral reefs thrived in the sunny and warm shallow seas. From the "Old One" Cameroceras, whose carapace was up to 9 meters long and looked like a swimming telephone pole, to the "old predecessor" Jamoytius of the phylum Chordata, all kinds of new animals appeared in the Silurian oceans and replaced the declining Ordovician fauna.

The shell of the early  was a simple flat spiral structure, while the appearance of the later  varied. Most of them were smooth spindle-shaped, thick in the middle and sharp at both ends. The Chinese translation of "" also comes from this: in 1829, Fischer de Waldheim named the genus Fusulina, and its root fusu means spindle in Greek; Mr. Li Siguang, the founder of modern geology in my country, added a worm radical to the word "筳", which refers to "the bamboo tool used for winding silk in ancient spinning", and created the Chinese character "", which was first used in the paper "Fusulina Family in Northern China" published in 1934.

Li Siguang's head portrait, located in the China Geological Museum | Tuchong Creative

Don't underestimate the simple calcite shell of the foraminifera. A 2017 study showed that the shell of the foraminifera has a complex multi-layer structure under an electron microscope. This unique structure shows that the order Foraminifera can coexist with unicellular algae, cyanobacteria or other microorganisms that can photosynthesize, and provide themselves with energy through photosynthesis; this "unique skill" that evolved for the first time in the phylum Foraminifera may be the secret to the foraminifera's continued prosperity over a long period of time.

Fossils of the order Pseudocimidae, stored in the Li Siguang Memorial Hall in Huangzhou, Hubei Province | Huangchenhai / Wikimedia Commons

The extinction event at the end of the Landavritian Stage wiped out 50% of trilobite species and 80% of conodont species in the world's oceans. However, the order Cercopithecidae survived this extinction event. Not only did the species become more and more prosperous over time, but the size became larger and larger, and the shape became ever-changing: in addition to the "basic" spindle-shaped shell, there are also convex mirror-shaped, disc-shaped, spherical and cylindrical shells. Cercopithecidae fossils have been found on all continents in the world except Antarctica, which is enough to glimpse their prosperity at the time. The order Cercopithecidae also survived two other extinction events in the Silurian Period, and the family became more prosperous and powerful.

Little knowledge about black-scaled cockroach snake

Conodonts are not stones, but teeth of small jawless fish. They are relatives of the living lampreys and hagfishes, 1-40 cm long, with slender, segmented and bilaterally symmetrical bodies, huge eyes and sharp serrated teeth. In the oceans at that time, they mainly preyed on zooplankton, including the order Pterops, and were once very prosperous.

Conodont | Derek EG Briggs / Wikimedia Commons

A spectacular extinction

The time has come to the Viscenian stage of the Carboniferous period, 346.7-330.9 million years ago, when the sea creatures reached their peak. Compared with the Silurian period, the Carboniferous ocean was more vibrant and full of many bizarre prehistoric "sea monsters".

The main large vertebrates in the ocean at that time were various cartilaginous fish of the Holocephalus subclass, and the top of the marine food chain was the Eugeneodontida represented by the scissor-toothed shark Edestu. The largest scissor-toothed shark was over 6.7 meters long, with scissor-like upper and lower jaws and serrated teeth, showing that they were terrible predators. Trilobites and other "old guards" of the previous dynasty did not leave the stage either. In the ocean at that time, the Eugenea occupied the same ecological niche as today's foraminifera relatives. As the cornerstone of the food chain, they provided for countless large and small marine animals.

Helicoprion, a Eugenean shark with bizarre spiral teeth | James St. John / Flickr

No dynasty can prosper forever, and the Yumu are no exception. At the end of the Permian period, about 251.9 million years ago, a series of violent eruptions occurred in volcanoes in what is now Siberia. The large amount of carbon dioxide released by volcanic activity led to severe climate change, causing large-scale warming, hypoxia and acidification of the global ocean. For plankton living in the surface of the ocean, especially foraminifera like the Yumu that obtain energy through photosynthesis and have shells made of calcium carbonate, such changes are undoubtedly fatal.

A fossil of a genus in limestone | James St. John / Wikimedia Commons

It is difficult for them to form shells in the increasingly acidic seawater, and the symbiotic photosynthetic microorganisms may also escape from their body tissues due to high water temperatures, just like the corals that are bleached today due to high sea temperatures. Once the marine zooplankton represented by the order of the order Pseudozoa disappears, it will be like a tall building with its foundations dug out. The animals at the top of the food pyramid will inevitably go extinct due to the loss of their food sources.

The end-Permian mass extinction was the most serious extinction event in the history of life on Earth. 81% of marine life and 70% of terrestrial vertebrates disappeared forever from the Earth, including the last order of the genus Triassic. The glorious movement of life was forever ended in a horrific disaster that destroyed the world. It took 3 to 5 million years for the Earth's biosphere to recover its vitality before the mass extinction until the Middle Triassic.

Full-length portrait of Li Siguang, located at Chongqing University | Tuchong Creative

In the modern world's oceans, there are still a large number of foraminifera. Like the extinct forams, they are small in size and numerous in number. As the cornerstone of the marine food pyramid, they support countless marine animals, from dense schools of fish to huge whales. However, like the forams, they are very sensitive to slight changes in sea temperature and pH, and are particularly vulnerable to climate change in a short period of time. Today, when climate change has become a severe challenge facing all mankind, looking back on the process of the forams from prosperity to extinction may give us some inspiration as we face an increasingly uncertain future.