They discover a distant relative of spiders that lived 450 million years ago

A species of arthropod that until now was unknown has been discovered due to its 450 million year old fossil remains. The fossilized specimen has been preserved three-dimensionally in pyrite. The new species, Lomankus edgecombei, is distantly related to spiders, scorpions and limulids.

The discovery is the work of a team led by Luke Parry, from the University of Oxford in the United Kingdom.

The fossil was found in a paleontological site in the state of New York, USA, which contains a layer of rock housing multiple trilobites with incredibly good preservation.

The animals preserved at that site lived in a hostile, low-oxygen environment that allowed pyrite to replace parts of their bodies after being buried under sediments, giving rise to spectacular three-dimensional fossils of a striking golden color, as if they were made of gold.

The new species belongs to the group of megaqueiros (or megaqueirans), an emblematic group of arthropods with a large modified leg, a type of arm, at the front of its body. Many of them used this appendage to capture prey.

Megaqueiros such as Lomankus edgecombei were very diverse during the Cambrian period (between 538 million and 485 million years ago), but were believed to have largely become extinct by the Ordovician period (between 485 and 443 million years ago). .

This discovery offers important new clues to solving the old puzzle of how arthropods developed head appendages: one or more pairs of legs located at the front of their bodies that were modified to serve specialized functions such as detecting the environment. immediately and capture prey. Some of these appendages are the antennae of insects and crustaceans, as well as the pincers and fangs of spiders and scorpions.

Artistic recreation of the appearance that typical adult individuals of Lomankus edgecombei most likely had in life. (Image: Xiaodong Wang)

“Today, there are more species of arthropods than any other group of animals on Earth. Part of the key to this success is its highly adaptable head and appendages, which have adapted to various challenges like a biological Swiss army knife,” highlights Parry.

While other megaqueiros used their large front appendage to capture prey, in Lomankus the claws typical of this one are greatly reduced, with three long and flexible whip-shaped flagella at the end. This suggests that Lomankus used this frontal appendage to perceive the environment, rather than to capture prey, indicating that it led a very different lifestyle from its older evolutionary relatives from the Cambrian period. It appears that, unlike other megaqueiros, Lomankus edgecombei lacked eyes, suggesting that it used its frontal appendage to search for food in the dark, low-oxygen environment in which it lived.

“Rather than representing an ‘evolutionary dead end’, Lomankus shows us that megaqueiros continued to diversify and evolve long after the Cambrian, with the once-fearsome large appendage now performing an entirely different function,” says Parry.

The study is titled “A pyritized Ordovician leanchoiliid arthropod.” And it has been published in the academic journal Current Biology. (Fountain: NCYT by Amazings)