The 300-million-year-old penny-sized creature, called Aphantomartus pustulatus, is a trigonotarbid -- part of an ancient group of arachnids that were among the first animals to colonize land. The burly eight-legged predator had a hard, segmented exoskeleton like a modern beetle, and scientists never suspected that it could spin a web -- until now.

The finding -- based on the remarkably well-preserved arrangement of tiny bumps called microtubercle rows along the creatures hindmost legs -- could shed light on the early evolution of arachnids, silk use, and life on land.

If trigonotarbids did spin silk like a spider, they had the right structures in the right places to do it, said Cary R. Easterday, a masters degree student in geological sciences at Ohio State. I suspect that other microtubercles located elsewhere on the body may have served as silk-producing structures, but I have no hard evidence yet.

Alternatively, the bumps could be cleaning structures, or specialized hairs that triggered fight-or-flight responses.

I want to be clear that these microtubercle rows are not conclusive evidence of silk-spinning in trigonotarbids, Easterday cautioned. But the evidence is very intriguing.

Ohio State University scientists reported their conclusions today at the
annual meeting of the Geological Society of America in Seattle.

Trigonotarbids, such as these ones preserved in a coalmine in eastern Ohio, coexisted with early spiders, Easterday explained. Early insects were probably their main food source.

Scavengers and bacteria normally destroy the thin, delicate exoskeletons of arachnids and insects when they die, but something about the chemistry of the fossil site preserved the fi
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Contact: Cary R. Easterday
Xenoblatta@hotmail.com
206-650-9747
Ohio State University
5-Nov-2003