100-Million-Year-Old "Chimera" Arachnids In Amber Shine A Light On The Construction Of Spiders

Robin Andrews 05 Feb 2018, 16:00

Spiders are an evolutionary extravagance, no matter whether you consider them to be misunderstood mischief-makers or malevolent monsters. Their history extends back tens of millions of years, and today, they can be found all over the world, occupying the shadows and nooks in the corners of our eyes.

Palaentologists are often fascinated by these eight-legged marvels, and two new studies published in Nature Ecology & Evolution highlight why. These utterly captivating specimens, members of a new species found trapped in Burmese amber, are 100 million years old – and the creature's mix of ancient and somewhat contemporary features are causing something of a schism.

In some ways, it resembles a modern specimen: it contains, for example, multi-segmented spinnerets, which are used to spin silk and create spectacular web patterns. At the same time, it’s a little alien: it’s adorned with tail-like ornaments named telsons that are far more common today in scorpions.

It’s fitting, then, that the species has been named Chimerarachne yingi, whose genus name roughly translates to “chimera spider.”

Both papers feature researchers from across the world, but both are led by the Chinese Academy of Sciences. The first paper concludes that this species represents one of the first true spiders, part of the extant order Araneae. The second study considers the species of encapsulated beastie to be part of an order of extinct spider relatives, the Uraraneida.

Regardless of which conclusion is ultimately proven to be correct by further research, both have powerful implications for how we understand spider evolution.

Ventral view. Bo Wang

If it’s the former interpretation that’s borne out by additional analysis, then we know that it represents one of, if not the earliest branches of the true order of spiders. If it’s the latter, then, as the authors of the paper explain “the new fossil extends the record of Uraraneida 170 million years towards the present, thus showing that Uraraneids and spiders co-existed for a large fraction of their evolutionary history.”

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