The discovery in Canada of three arthropod fossils has pushed back the dates of the first fully terrestrial animals in North America by tens of millions of years. A report in tomorrow's issue of Nature proposes that, at nearly 400 million years old, the animals--including a millipede and a scorpion--rival the age of arthropods found in Britain and are among the largest and best preserved land animals from that early date.
When Patricia Gensel, a biology professor at the University of North Carolina, Chapel Hill, and her husband spotted the first of these ancient animals, a millipede, curled up in the cliffs near Gaspé Bay, Quebec, they thought it was a shrimp, she recalls. She passed the fossil on to paleobiology expert William Shear of Hampden-Sydney College in Virginia, who identified the creature, as well as two other animal fossils that Gensel unearthed on later expeditions in New Brunswick, Canada.
Shear estimated the age of the specimens--between 390 million and 395 million years--from the kinds of plant spores embedded in the same rock. His estimate would place them in the early Devonian period and is "extremely early for what we know" in North America, says Jarmila Kukalova-Peck, a paleoentomologist at Carleton College in Minnesota.
The most exciting of these finds, says Shear, was a fully preserved 8-centimeter-sized scorpion, complete with actual pieces of skin pressed into the rock. It yielded clear evidence of a terrestrial lifestyle. After dunking the fossil in hydrofluoric acid to remove minerals, Shear identified the scorpion's lungs as those of a landlubber because of the special "book lungs," designed to circulate air between the "pages." The scorpion and its compatriots, he concludes, were "beautifully adapted to life on land."