for National Geographic News
Add the lamprey to the list of "living fossils."
A 1.7-inch (4.2-centimeter) fossilized specimen found in an ancient South African lagoon shows that the bloodsucking, eel-like fish hasn't changed much in 360 million years, according to a new study to be published tomorrow in the journal Nature.
(See another newfound "living fossil": the first new mammal discovered in Europe in a hundred years.)
The ancient lamprey attached its toothy, suckerlike mouth to, for example, prehistoric sharks almost exactly the same way that modern lampreys latch onto other fish today, the study says.
As the prehistoric lamprey's hosts went extinct or evolved into new species, "the lamprey simply evolved into a lamprey,'' said study co-author Michael Coates, a biologist at the University of Chicago in Illinois.
Like modern lampreys, this ancient lamprey had a backbone made not of bone but of cartilage—the generally translucent, somewhat flexible substance that gives human noses and ears their shapes and that makes up shark skeletons.
Perhaps most important, the new discovery is "the first lamprey fossil to give us a good view of the mouth,'' Coates said.
The fossilized lamprey had a jawless mouth ringed with horny teeth, like modern lampreys. This jawless mouth sets the lamprey and its cousin the hagfish apart from all other modern vertebrates—animals with backbones.
It is believed that jawless marine animals were the first vertebrates and that they emerged sometime after 540 million years ago.
The Great Divide
When the fossilized lamprey lived, there were probably many types of jawless vertebrates. Except for the lamprey and hagfish, all of them seem to have died out.
"This fossil shows that the lampreys are the closest living representatives of backboned animals of that era,'' Coates said.
SOURCES AND RELATED WEB SITES