Scientists Find 100-Million Year Old Spider Relative

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Scientists have reported finding fossils of a spider-like creature in Myanmar. Two groups of researchers described their finds in papers published in the journal “Nature Ecology & Evolution.”

The spider, Chimerarachne yingi, lived during the Cretaceous age 100 million years ago. It owes its genus name to the Chimera from Greek mythology, a hybrid monster with parts from several different animals. Unlike modern spiders, C. yingi had a long, whip-like tail. It did have spinnerets, so it could have produced silk, but the scientists don’t believe it wove webs. Different spider species have also used silk to make hammocks, wrap eggs or leave trails to help them find their way home.

The researchers aren’t entirely sure what C. yingi did with the tail, particularly if it had a venomous bite like modern spiders. While the scientists could detect fangs, they did not find an opening for a venom gland. Some of the scientists, however, speculate that C. yingi used the tail as a sensory organ. As C. yingi was found in amber or fossilized tree resin, some of the researchers believe the spider lived on or near trees.

Spiders as a group first appeared around 315 million years ago, and they descended from arachnids that had tails. According to the scientists, C. yingi occupied a spot between true spiders and uraraneids, which were tailed arachnids that first appeared during the Paleozoic. C. yingi also resembles the present-day mesotheles, which are the most primitive living spiders and are found only in parts of Asia. Some researchers speculate that C. yingi may have living descendants. It was tiny – less than three millimeters long — and many forests in Myanmar have not yet been thoroughly explored. As modern, tailless spiders had already evolved by the mid-Cretaceous, C. yingi was not an ancestor.

C. yingi had a mixture of primitive and modern traits. The tail, for example, was a primitive trait, while the spinnerets were a modern feature and resembled those of the mesothele spiders. The scientists also identified pedipalps that the males used to transfer sperm.

With over living 47,000 species, spiders are among the most successful of animal groups. During their millions of years of evolution, they have evolved such novel features as spinnerets.

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