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Fossils flesh out early vertebrates.

Fossils flesh out early vertebrates

The oldest known vertebrates, a collection of remarkably well-preserved remains of 30 jawless fish, have been discovered by an international team of paleontologists in the mountains of southern Bolivia, according to an announcement last week by the National Geographic Society in Washington, D.C., which funded the expedition.

The fossils were embedded in large stone slabs that date to about 470 million years ago, when much of present-day Bolivia was covered by ocean. At least 10 of the specimens are virtually complete, with even the tail sections intact, says expedition director Philippe Janvier of the French National Research Center in Paris.

"This is one of the most exciting and important discoveries in lower-vertebrate studies in the last 50 years," says vertebrate paleontologist David K. Elliott of Northern Arizona University in Flagstaff, who has seen the Bolivian specimens.

These ancient fish were probably poor swimmers that avoided deep water, notes Janvier. Bony plates protected the rounded head of the creature. Its body was covered with thin scales that ended near a narrow tail.

The fossil fish, which are up to 18 inches long and 6 inches wide, appear to represent a new genus, according to Janvier. He and his co-workers have dubbed the genus Sacabambaspis, after a village located near the fossil discovery.

Fragmentary remains of fish from about the same time or slightly later have been found in Australia and North America. Those found in Australia closely resemble the Bolivian fossils, says Janvier, while the North American specimens most likely belong to a different group of marine species.

Another vertebrate paleontologist familiar with the new fossils, Hans Peter Schultz of the University of Kansas in Lawrence, says they are similar to several ancient fish imprints previously found in Australian sandstone. The imprints are almost as complete as the new fossils, he notes, and date to nearly 470 million years ago. However, no fossil remains were found with the impressions.

"The Bolivian find shows that there was a broader variety of marine forms at that time than was expected," says Schultz. "Since fossils from around 470 million years ago are now known to be widespread, there must be a long vertebrate history before that time that we have no record of."

Jawless fish, whose modern counterparts include lampreys and hagfish, have been considered the earliest known vertebrates, or creatures with a backbone, for more than a decade. The bony spine typical of most vertebrates is replaced in jawless fish by a flexible rod similar to cartilage.
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Author:Bower, Bruce
Publication:Science News
Date:Jan 9, 1988
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