The discovery of a near-perfect 417-million-year-old fossil of a scorpion-like creature in a Canadian quarry has revealed how adaptations in the armourlike "exoskeletons" of primitive organisms first allowed for their excellent preservation in stone and began giving science its rich record of animal evolution.

The findings, published in the latest issue of the journal Geology, promise "major implications for our understanding of the organic fossil record," says a summary of the study released by the Carnegie Institution for Science in Washington, D.C.

The ancient specimen was collected from a Fort Erie, Ont., gravel pit that's well known to paleontologists as a prime target for fossils of the extinct "eurypterid" from the Silurian era of Earth history. The species is believed by some to be an ancestor of today's horseshoe crab.

The fossil from the Ridgemount Quarry near Niagara Falls was found to contain the faint, chemical traces of proteins scientists believe were used to construct the hard outer shell of many species that began to show up in the fossil record about 500 million years ago.

The telltale protein signature detected in the Canadian eurypterid, now held at Yale University's Peabody Museum of Natural History, represents the earliest proof ever of such strengthened exoskeleton construction.

George Cody, the U.S. researcher who led a team of eight American and British scientists in studying the fossil, said the discovery could point the way to developing new techniques to detect the presence of much older organisms that paleontologists can't currently identify in rock deposits.

"The most important result is that we solved the long-standing problem of how these fossils, so crucial to the fossil record, are preserved," said Cody, a senior researcher in Carnegie's geophysical laboratory.

His team's study of the Ontario specimen was bolstered by analysis of a 300-million-year-old fossilized scorpion from a site in Illinois that also yielded evidence of a sturdier exoskeleton. "Up to this point," he said, the prevailing view among scientists was that trace remnants of the shell-like coverings of extremely old arthropod species would "hydrolyze away to nothing," and thus couldn't be detected in their fossil impressions.

Before Cody's team identified the exoskeleton chemicals in their study, the oldest example in science came from an arthropod fossil dated to just 80 million years ago, when creatures as complex as dinosaurs were roaming the Earth.