Largest spider fossils ever found create new branch of spider family tree

Farmers digging up fossils near Daohugou, China have now provided researchers with the largest spider fossil ever discovered, and this new find is helping to define how spiders evolved.

Spiders these days can grow pretty big. Species like the goliath birdeater in South America and the giant huntsman spider in southeast Asia can have leg-spans of up to 30 centimetres and bodies that are around five centimetres long. However, millions of years ago, back in the Jurassic period, there were still spiders that you wouldn't want to find crawling around in your bathroom. According to researchers with the University of Kansas, a fossil discovered just recently in Inner Mongolia shows a spider with a body over 1.5 centimetres long, and its first leg (the long one stretched out in the image above) was nearly 6 centimetres long. That gives this spider a roughly 15 centimetre leg-span!

This spider fossil, a male, can now join a female counterpart of the same species that was discovered around three years ago. Paul Selden, a professor of invertebrate paleontology at the University of Kansas who also found the first instance of this species, says that the find is important because "it's intermediate between the more primitive kinds of the araneomorph, or 'true' spiders, and the well-known orbweavers that we see around us commonly today."

Orbweavers are the common web-building spiders we see today.

Not only do these two spiders represent the biggest spider fossils ever found, but they've actually created a completely new branch on the spider family tree. When the female was discovered, the species was given the name Nephila jurassica. However, because so many of the fine details of the male spider were preserved in this new fossil, such as the foot claws, hairs and genital organs, the researchers were actually able to figure out that these two belonged to a completely different family. This new branch is now called Mongolarachnidae, and the species has been renamed Mongolarachne jurassica.

"Scanning electron microscopy came to the rescue with some of these features, such as the structure of the hairs, and helped to place the species more accurately," Seldan said in a university press release. "This is the first time this technique has been used on fossil spiders in the rock."

[ More Geekquinox: Polar vortex settles in over Ontario as Maritimes brace for another blizzard ]

The researchers are hailing the importance of this find, not only to tell us about the past, but to also give us clues about the future.

"First, it is an amazing spider," Selden said. "It’s the largest fossil spider — and great to have both male and female. Second, research into the anatomy reveals details of how it lived and interacted with its insect prey. These give clues to what the climate was like at the time, and we can then track the fate of these ecosystems as they evolved through time and changing environments. Understanding the processes involved helps us to predict how man-made changes might affect the Earth's climates and biodiversity."

(Photos courtesy: University of Kansas)

Geek out with the latest in science and weather.
Follow @ygeekquinox on Twitter!