While fossil bones found around the world indicate the diversity of dinosaurs during the Mesozoic Era, their soft tissues usually decomposed long before fossilization could take place. Now an exciting discovery of more than 60 specimens of fossilized dinosaur skin suggests a novel process for the fossilization of soft tissue, and gives vital hints to the prehistoric environment of northern Wyoming.

Geologist Dr. Marilyn Wegweiser (Georgia College & State University) and colleagues announced the discovery at the Society of Vertebrate Paleontologists meeting in St. Paul, Minnesota, on Thursday, October 16. The skin finding will also be the cover story in the third issue of The Sedimentary Record, coauthored by Wegweiser, Brent Breithaupt (University of Wyoming), Loren Babcock, Ethan Skinner (both of Ohio State University), and Joseph Sheffield (Georgia College and State University).

"This find is extremely significant because it is the first time anyone has ever analyzed dinosaur skin fossils to identify the process that preserved them," said Wegweiser. "While a number of skin fossils have surfaced, they are usually preserved as imprints of the skin. In this case, the skin was replaced by minerals. Rather than merely an imprint, this is a fossil of the skin itself."

With the help of Earthwatch volunteers, Wegweiser found the skin fossils in the Lance Formation (Upper Cretaceous) at the This Side of Hell Quarry in Park County, Wyoming. The skin, with non-overlapping polygonal scales, is part of a larger fossil quarry of broad significance, including the excellently preserved skeleton of a large, lambeosaurine dinosaur, perhaps more dinosaurs, and associated footprints.

The dinosaur skin in the fossils was replaced by a mineral called pyrolusite, indicating a very specific environment in which the lambeosaur came to rest. Wegweiser explains that pyrolusite precipitates out of water only under very specific conditions. The mineral is known to form under conditions of mixing marine and fluvial, or river, waters, so it is often used as an indicator of paleoshorelines.

"When this animal died, 67 million years ago, it was in a nearshore environment, a humid tidal flat with paleomagnolia trees, part of the lambeosaurine diet," said Wegweiser. "This finding pushes the shoreline much farther west of where it is thought to lie at the time. It also tipped us off to why the associated bones are in such great shape, but that's another story."

The skin discovery began with a 5-centimeter specimen found among quarry tailings by Earthwatch volunteer Pat Seostrom of Patchogue, New York, in July 2002. Another Earthwatch team member Ellen Turner, a student at William and Mary, is credited with lugging down from the remote quarry a large specimen of skin embedded in rock, weighing perhaps 20 kilograms, which was used in the authors' analyses.

"Without Pat's initial find we may not have looked so closely and made this important discovery," said Wegweiser. "I credit Earthwatch volunteers for clearing away the quarry, layer by layer, so carefully. I suspect that there may be skin fossils at many other dinosaur quarries, but excavators overlook them in their effort to dig out the bones."

Wegweiser has founded the Wyoming High Desert Research Institute and Museum to serve as a repository for the important finds at This Side of Hell quarry and other dinosaur sites in Wyoming.

For more information, see "Dinosaur skin fossils from This Side of Hell, Wyoming: Paleoenvironmental implications of an Upper Cretaceous Konservat-Lagerstätte in the Lance Formation." Wegweiser, M.D., et al. The Sedimentary Record, vol 1:3.


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