Biggest Spider Fossil Now Has Mate — But It's Complicated: Page 2

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First of all, the male was remarkably quite similar in size to the female, with a body that measures 0.65 inches (1.65 centimeters) long and a first leg stretching 2.29 inches (5.82 cm).

"This is rather strange," Selden said. "In the modern orb weavers, there is quite a lot of sexual dimorphism," with a huge female and a tiny male.

Compared with Nephila male spiders, this newfound fossilized male had more primitive-looking pedipalps — the sex appendages between a spider's jaws and first legs that it uses to transfer sperm to the female. And it had a more feathery hairstyle: The fossil was preserved so well that Selden could look at imprints of the spider's hair under an electron microscope. Instead of one or two scales along each bristle, Selsen said he saw evidence that this spider had "spirals of hairlets" along the strands covering its body.

PHOTOS: Golden Spider Silk Makes Rare Cloth

The researchers think the fossilized spiders may actually be more closely related to spiders in the Deinopoidea genus, also called ogre-faced spiders. Arachnids in this group are considered orbicularians. They also make orb-shaped webs, but their silk is more "woolly," Selden said, with a stickiness that's more like Velcro than glue.

Revising their original labeling of the giant fossilized female spider, the researchers created a new genus and species name for the pair: Mongolarachne jurassica. Selden and colleagues also created a branch for Mongolarachne on a phylogenic tree, placing it quite close to the stem where orbicularians originate.

The study was published online Dec. 7 in the journal Naturwissenschaften.

Original article on LiveScience.

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