Ancient amphibians found in Iowa.Ancient amphibians amphibians members of the animal class Amphibia. Includes frogs, toads, newts, salamanders and cecilians all capable of living on land or in water. found in Iowa Geologists in Iowa have discovered a large fossil bed containing the oldest well-preserved land vertebrates known to exist in North America North America, third largest continent (1990 est. pop. 365,000,000), c.9,400,000 sq mi (24,346,000 sq km), the northern of the two continents of the Western Hemisphere. . Dated at 335 million years old, from the Carboniferous period Carboniferous period (kärbənĭf`ərəs), fifth period of the Paleozoic era of geologic time (see Geologic Timescale, table), from 350 to 290 million years ago. , these fossils of early amphibians will help scientists trace the evolutionary path from water to life on land. "I would say it's a major discovery," says John R. Bolt of Chicago's Field Museum of Natural History Field Museum of Natural History, at Chicago, Ill. Founded in 1893 through the gifts of Marshall Field and others, it was first known as the Columbian Museum of Chicago and later (1943–66) as the Chicago Natural History Museum. . Worldwide, only 22 fossil sites List of fossil sites: Africa Africa Site Country/State Age Afar Depression Ethiopia Pliocene Ahl al Oughlam Morrocco Late Pliocene Awash River Ethiopia Pliocene Baharija Formation Northern Africa Upper Cretaceous of comparable age are known, and most of those have yielded limited numbers of fragmentary specimens. At the Iowa site, Bolt says, "the material is quite well preserved." He reports the find in the June 23 NATURE along with R.M. McKay and B.J. Witzke of Iowa's Geological Survey Bureau in Iowa City and M.P. McAdams of the William Penn College in Oskaloosa, Iowa. The researchers found two types of tetrapods, or four-legged animals, that do not readily fit into any known species. These creatures reached about 3 to 5 feet in length and probably resembled giant salamanders, McKay says. While they had well-developed legs for walking on land, they apparently spent most of their time in the water. Of particular interest is an amphibian amphibian, in zoology amphibian, in zoology, cold-blooded vertebrate animal of the class Amphibia. There are three living orders of amphibians: the frogs and toads (order Anura, or Salientia), the salamanders and newts (order Urodela, or Caudata), and the that was informally dubbed proto-anthracosaur. This newly identified animal combines advanced amphibian characteristics with features similar to those of the most primitive known tetrapods. Paleontologists have long debated which form of fish spawned the first amphibians to crawl onto land. The proto-anthracosaur "may lead to some hypotheses as to what sort of fish ancestors we should expect for the early tetrapods," Bolt told SCIENCE NEWS. In examining the fossil bed, the researchers also identified many fish species that may have served as food for the strong-jawed, toothy amphibians. However, McKay notes, "I don't know Don't know (DK, DKed) "Don't know the trade." A Street expression used whenever one party lacks knowledge of a trade or receives conflicting instructions from the other party. who was preying on whom because some of the fish were about 10 feet long. And they had big teeth." |
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