Discovery of the oldest ancestor of spiders

Discovery of the oldest ancestor of spiders

A team of paleontologists announces the discovery of a small fossil exceptionally well preserved in Canada. An ancient predator, ancestor of spiders and scorpions, evolving about 500 million years ago.

It is a pair of eyes sparkling in a shale rock in Burgess, British Columbia, which first caught the attention of researchers. The almost sure sign of the presence of an ancient creature. And not just any Jean-Bernard Caron and his team at the Royal Ontario Museum have identified a new species – Mollisonia plenovenatrix – the oldest known chelicera. This superclass now includes arachnids, merostomes and pycnogonids. In other words, this creature, about 500 million years old, is a direct ancestor of crabs, scorpions and other spiders. It’s even the oldest revealed. The details of this study are published in the journal Nature.

He may not have been big enough – the size of an inch – but seemed armed to be a real predator on the seabed. Physically (pictured above) imagine two egg-shaped eyes. Several sections of limbs allowed him to move in the sediments. He also had a “multi-tool” head, with members able to feel, grasp, crush or chew. But it’s the small pair of structures, just in front of his mouth, that really excited the researchers.

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It was indeed a chelicère, an appendage common today to arachnids, merostomes and pycnogonides. “These same claws are visible on all members of the family Cheliceres: we speak of 115 000 different species, and here is their ancestor,” enthuses Jean-Bernard Caron. These small structures probably served him to seize, kill, and why not cut his prey.

It should also be noted that this species already seemed particularly well evolved. For researchers, the origin of Cheliceres must therefore be even deeper. There may be 540 million years ago, when the famous Cambrian “explosion” began. Time when all animal, plant and bacterial species have really started to diversify.

The researcher also takes the opportunity to remind us of the importance of these Burgess shales, found in the heights of the Canadian Rockies. A region particularly rich in Cambrian fossils. According to him, there would still be a lot to do. “We could work there for decades and still feel like we only scratched the surface,” he says. For those interested, the researcher advises focusing on the eyes. “For many fossils, this is the first thing we see: two bright spots in a rock.”

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Eric Thomas

Eric, originally from Nigeria, currently resides in Florida and covers a wide range of topics for The talking Democrat.