Scientists have unearthed the largest spider fossil ever found.

The spider, a new species called Nephila jurassica, stretches about two inches from end to end. It was found in a fossil-rich rock formation near Daohugou village in northeastern China. The fossil dates back to the Middle Jurassic, about 165 million years ago, researchers reported in the April 20 Biology Letters.

Spiders from the same family still exist today. Female giant golden orb-weaver spiders can grow to a whopping 4 or 5 inches in diameter (although males tend to be less than a quarter that size). These spiders are known for spinning huge webs of golden silk and have been known to trap bats and small birds.

But Nephila have a surprisingly sparse fossil record. Before N. jurassica, the oldest Nephila spider fossil was about 34 million years old. The newly discovered fossil means that this spider family originated 35 million years earlier than thought, and that the genus Nephila is 130 million years older than previously suspected.

The ancient spider probably originated somewhere on Pangaea, the supercontinent that once contained all seven modern continents. The spider probably spread before Pangaea broke up, the researchers say. Because modern golden orb spiders usually live in tropical climates, the fossil suggests that modern-day Daohugou was much warmer and more humid than it is today.

The new specimen is also just the second female Nephila fossil yet described. Ancient male N. jurassica were likely much smaller, just as they are today, but researchers will have to find one to be sure.

Images: 1) Nephila jurassica (Paul Selden). 2) A giant golden-orb web exceeding 1 meter in diameter, spun by a modern Nephila inaurata spider (Matjaz Kuntner). 3) A closeup of Nephila jurassica’s right leg, showing tiny fossilized hairs.

Citation:
“A golden orb-weaver spider (Araneae: Nephilidae: Nephila) from the Middle Jurassic of China.” Paul A. Selden, ChungKun Shih and Dong Ren. Biology Letters, in press. DOI: 10.1098rsbl.2011.0228

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