By DAVID WILLIAMSON
UNC-CH News Services
(Embargoed) CHAPEL HILL -- The oldest evidence of larger animals living on land in North America has been discovered by a University of North Carolina at Chapel Hill biologist and her husband.
The animals, large only when compared with microscopic organisms, date back almost 400 million years to the Early Devonian age and some 200 million years before dinosaurs appeared. Hardly cuddly creatures, they were scorpions, millipedes and related arthropods measuring up to four inches.
"These fossils are conclusive proof that large land-dwelling arthropods existed early in the Paleozoic," said Dr. Patricia Gensel, professor of biology at UNC-CH. "The only older ones, which date to about 420 million years in the Upper Silurian period, were spider relatives and centipedes found in western England and are much smaller."
Arthropods also have been found in Scotland, Germany and New York state that are similar in age or younger than the new finds, but are smaller or poorly preserved, Gensel said. The Canadian fossils, among the largest of their kind ever found, also are among the best preserved, showing body outlines and organic remains.
A report on the discoveries appears in Thursday's (Dec. 12) issue of the journal Nature. Besides Gensel, authors are Drs. William A. Shear of Hampden-Sydney College in Virginia and Andrew J. Jeram of the Ulster Museum Botanic Gardens in Belfast, Northern Ireland.
Gensel and her husband William, a Durham businessman, found some of the specimens during a 1980 collecting trip along the cliffs of Gaspe Bay, Quebec. The biologist later found other specimens while collecting in New Brunswick, Canada. Since they knew they had found something significant but not what, she eventually turned to Shear and Jeram, experts on ancient arthropods, for help in identification.
The scientists confirmed that the creatures lived on land because they found in the scorpions evidence of book lungs -- sheets of membranes containing blood vessels that allowed air breathing. Marine animals never have book lungs, and no clam shells or other evidence of ocean life could be found in the exposed sediments.
Identifying the creatures, which have organically preserved parts and pieces of the hard outer coat known as cuticle as well as impressions of their body structures, took so long because the Gensels had earlier sent them to paleontologists in Europe who could not identify them.
Along with only about 30 other scientists around the world, Gensel, a paleobotanist, specializes in studying fossils of some of the earliest land plants, such as club mosses and the ancestors of ferns. Among her previous scientific contributions has been new information about which early plants lived where, what their structure was and how they evolved. She has documented several new types of extinct plants and also early stages in the evolution of leaves like those found in modern ferns and seed plants.
"Until about 10 years ago, it was felt that there was almost nothing in the way of land animals during this time, and so discovery of the arthropods has really altered the picture," Gensel said. "The Devonian has often been called `the age of fishes' since there were so many fish and so few land animals around."
Finding land animals has opened up the possibility of plant-animal interactions in early land environments. Interestingly, she said, none of the animals found so far are of the type that prey on living plants, instead eating decaying matter or each other.
"Damage found among plant tissues suggests that herbivores also existed," Gensel said. "We need to find more animal fossils to confirm that possibility."
Studying early plants and animals is important, the researcher said, because it shows how life moved from water onto the previously rocky landscape and then expanded rapidly, both causing and responding to global environmental change. The prior existence of several types of algae and other microorganisms may have paved the way for more complex plants to inhabit the land by pumping out oxygen to produce an atmosphere more like that of today and perhaps converting some rocky surfaces to thin layers of soil.
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Note: Gensel can be reached at 919-962-6937 (w) or 544-2881 (h).
Contact: David Williamson