Early Attempts At The Spider Included An Eight-Legged Weirdo With A Tail

In 2018, scientists described a new species of spider-like arachnid that lived 100 million years ago. Like modern spiders, it had spinnerets, a palpal organ for sperm transfer, and four paired walking limbs. Very much unlike modern spiders, however, it also had a tail.

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The study investigated two fossils, both of which were male, to explore an old evolutionary question: how did spiders evolve, and in what order did their characteristic traits appear?

Using microscopy and 3D imaging, they were able to examine the fossils’ minute details. It revealed they had spinnerets and silk spigots, just like modern spiders. It also had a narrow waist, known as a pedicel, but while the overall body plan was similar to that of a spider, it still had a segmented abdomen – something we don’t see in spiders.

Something else we don’t see in spiders is the long, whip-like appendage attached to its rear. It’s thought to represent a previously unrecognized lineage of tailed spiders, or spider-like creatures. They weren’t the ancestors of modern spiders, but existed alongside them. Sort of like a weird cousin (and we all have one of those).

The technical name for the appendage is a flagelliform telson, and it’s made up of lots of tiny segments, making it very flexible. We see similar structures in today’s whip scorpions, and it has many potential uses.

The tail may have been a sensory organ for navigating the environment, or could have been used as part of a defensive response to freak out would-be predators. Alternatively, it may have been a means of distraction, and could even have functioned like the tail of a lizard in breaking off as an escape strategy.

As for the big question: is it a spider? The authors believe it’s either the earliest known branch of true spiders, or a very close sister group. The discovery marked a big chapter in spiders’ evolutionary history, demonstrating that spider traits emerged like a mosaic, blending old with new. Hence the species name, Chimerarachne yingi, as in chimera.

That nuance probably isn’t going to make it any more popular among arachnophobes, however.