Two New Dinosaurs from Africa
Nov. 11 -- One dinosaur species was an evolutionary offshoot with a strange-shaped head and 600 teeth. The other was more primitive, remaining almost unchanged for 40 million years and surviving long after supposedly more evolved relatives went extinct in other parts of the world.
Two newly discovered species of large, long-necked, plant-eating dinosaurs from Niger illustrate the widely differing paces of evolution.
“There seems to be no preference in rate [of evolution],” says University of Chicago paleontologist Paul Sereno, lead author of an article in Friday’s Science describing the new dinosaurs. “I don’t know if we could have predicted that. We are the first to really show it.”
The Unchanging Dinosaur
In the steady and unchanging crowd is Jobaria tiguidensis, a 20-ton, 70-foot-long cousin of Apatosaurus (a genus better known to many as Brontosaurus), Diplodocus and other sauropod dinosaurs. (Jobar is a mythical creature among North African nomads; tiguidensis refers to cliffs near the discoverysite.)
What’s most intriguing about Jobaria is not its features, but that it appeared to be living in the wrong era. The two Jobaria specimens excavated by Sereno’s team, one adult and a smaller juvenile, date to about 135 million years ago, or after Apatosaurus and Diplodocus, which roamed in North America, had already died out.
But in appearances, Jobaria is more primitive than its earlier North American cousins. Its neck is relatively short, with only 12 neck bones, vs. 15 or more in more evolved sauropods, and it has spoon-shaped teeth, like the early sauropods, rather than the pencil-shaped teeth of later versions.
“It looks like it comes out of the Jurassic,” Sereno says, referring to the period from 200 million to 135 million years ago. “It’s sort of hanging on in Africa and doing quite well.”
Different Teeth for Different Food
Spoon-shaped teeth may have been more suited to dining on conifers, while pencil-shaped teeth are believed to be better fern munchers, possibly reflecting a shift in vegetation. Longer-necked sauropods have greater reach.
