Half-billion-year-old three-eyed animal reveals secrets of arthropod evolution

(ORDO NEWS) — Five hundred million years ago, an amazing animal the size of a shrimp swam in the seas of our planet: it had a round mouth studded with many teeth, spiked claws and three large eyes that provided a wide view.

Although this creature did not leave direct descendants, its bizarre anatomy allowed scientists to better understand how the evolution of the nervous system in modern arthropods – crayfish, spiders and insects – proceeded.

The world-famous Burgess Shale in western Canada is one of the world’s richest Cambrian paleontological sites , formed about half a billion years ago by a sudden underwater landslide.

A tragedy for marine life turned into good luck for scientists, because now they have in their hands thousands of specimens of bizarre animals that lived on Earth at the very beginning of the Paleozoic era .

The fossils are so well preserved that you can discern the smallest details of their structure – from the boneless limbs of an incredible hallucigenia to the elastic cord of the chord in the body of a graceful pikaya.

Naturally, the shelled creatures imprinted even better in the fine-grained rock, and the largest animals of the Burgess Shale are dinocarids , an extinct class of arthropods that grew up to 80 centimeters.

Fossils of dinocarids are not so common, moreover, they are often preserved in the form of separate fragments, so it can be difficult for scientists to restore the appearance of a whole animal.

Fortunately, the new species did not suffer such a fate, perhaps due to its small size: during a fatal landslide, several hundred small, from one to eight centimeters long, Stanleycaris hirpex died at once , and now the prints of their tiny bodies are in the Royal Museum Ontario .

Eighty-four samples were especially well preserved: the researchers were able not only to study the external features of the animal, but in the literal sense of the word to look into his head, analyzing the structural features of the brain.

It turned out that in stanlikaris the brain consisted of two parts, while in all modern arthropods it consists of three: the ancient animal “lacks” the third part, called tritocerebrum , which is responsible for the innervation of the mouth area and is closely related to the sympathetic nervous system.

In addition to the unusual structure of the brain, stanlikaris is notable for the non-standard number of eyes: he had three of them. The third eye was located between the two side eyes and was fully functional.

After studying similar formations on the prints of other dinocarids, which were less well preserved, scientists came to the conclusion that they were all three-eyed.

Since these creatures are relatives of the ancestors of the current crabs and dragonflies, it can be assumed that three-eyedness, along with a segmented brain, is a common feature of all ancient arthropods.

The discovery of stanlicaris allows us not only to imagine the evolutionary paths of modern animals, but once again appreciate the scientific value of the Burgess Shale, a unique “time capsule” that has survived to this day from time immemorial.

Listed as a UNESCO World Heritage Site in 1980, the site is sure to hold many more amazing secrets, and the stanlicaris is just one of the thousands of amazing animals found there, most of which are probably waiting for their paleontologists.

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