Thursday, April 21, 2011

[Geology2] Largest Fossil Spider Found in Volcanic Ash

I love when that happens . . . I think . . .

Largest Fossil Spider Found in Volcanic Ash

Fossil female golden orb-weaver spider (Nephila jurassica) from the
Middle Jurassic of China. CREDIT: … Charles Q. Choi, LiveScience
Contributor, charles Q. Choi, Livescience Contributor,

â€" Wed Apr 20, 7:54 am ET The largest fossil spider uncovered to
date once ensnared prey back in the age of dinosaurs, scientists find.

The spider, named Nephila jurassica, was discovered buried in ancient
volcanic ash in Inner Mongolia, China. Tufts of hairlike fibers seen on
its legs showed this 165-million-year-old arachnid to be the oldest
known species of the largest web-weaving spiders alive today – the
golden orb-weavers, or Nephila, which are big enough to catch birds and
bats, and use silk that shines like gold in the sunlight.

The fossil was about as large as its modern relatives, with a body one
inch (2.5 centimeters) wide and legs that reach up to 2.5 inches (6.3
cm) long. Golden orb-weavers nowadays are mainly tropical creatures, so
the ancient environment of Nephila jurassica probably was similarly
lush. [Image of fossil spider]

"It would have lived, like today's Nephila, in its orb web of golden
silk in a clearing in a forest, or more likely at the edge of a forest
close to the lake," researcher Paul Selden, director of the
Paleontological Institute at the University of Kansas, told LiveScience.
"There would have been volcanoes nearby producing the ash that forms the
lake sediment it is entombed within."

Spiders are the most numerous predators on land today, and help keep
insect numbers in check. So these findings help us "understand the
evolution of the insect-spider predator-prey relationship," Selden said,
suggesting that golden orb-weavers have been ensnaring insects and
influencing their evolution since the Jurassic Period. [Read: Ancient
Spider Guts Revealed in 3-D]

"There were many large or medium-sized flying insects around at that
time on which it would have fed indiscriminately," Selden said.

In modern golden orb-weaver species, females are typically much larger
than males. This new fossil was a female, suggesting this trend
stretches back at least as far as the Middle Jurassic, Selden said
â€" that is, back before the first known bird, Archaeopteryx, or
giant dinosaurs such as Brachiosaurus and Diplodocus.

Although this is the largest fossil spider known to date, it is not the
oldest. Two species from Coseley, England, Eocteniza silvicola and
Protocteniza britannica, both come from about 310 million years ago.

Selden and his colleagues are now investigating other fossil spiders
from China, "as well as those from elsewhere in the world â€"
currently Brazil, New Zealand, Australia, Italy and Korea," he said.

The scientists detail their findings online April 20 in the journal
Biology Letters.
Follow LiveScience for the latest in science news and discoveries on
Twitter @livescience and on Facebook.

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