THE VIRGINIAN-PILOT
Copyright (c) 1996, Landmark Communications, Inc.
DATE: Friday, May 17, 1996 TAG: 9605170489
SECTION: FRONT PAGE: A1 EDITION: FINAL
SOURCE: FROM WIRE REPORTS
LENGTH: Long : 115 lines
Exploring the Sahara in southeastern Morocco, paleontologists have found the fossil remains of two huge predatory dinosaurs. The discovery is seen as a major step in uncovering Africa's early fossil past and understanding the evolutionary changes in dinosaurs after the breakup of the continents.
The more spectacular of the finds is the gigantic skull and sharp teeth of a meat-eating creature that lived 90 million years ago and measured 45 feet from snout to the tip of its tail. The skull, with a length of 5 feet 4 inches, may be larger than the largest skull of a Tyrannosaurus rex, which lived 70 million years ago in North America and had long been considered the largest known terrestrial carnivore.
But this African dinosaur apparently was not as bright as tyrannosaurs; its brain cavity appeared to have half the volume of the later and more familiar predator. Scientists identified the fossil skull as belonging to a species first recognized in 1927 but poorly known until now: Carcharodontosaurus saharicus, which means ``shark-toothed reptile from the Sahara.''
The other discovery is the partial skeleton of a predatory dinosaur completely new to science. As reconstructed in the laboratory, the dinosaur is at least 25 feet long and, for a creature so large, has unusually long, slender limbs, suggesting that it was a swift and agile hunter. The fossil animal is named Deltadromeus agilis, or ``agile delta runner.''
``Nothing like Deltadromeus has been found on any other continent so far,'' Dr. Paul C. Sereno, a paleontologist at the University of Chicago who led the expedition that made the discoveries last year, said in an interview Thursday.
``I would not have wanted to be around when it was on the prowl,'' he said. ``It would have been a really ferocious, fast-moving hunter. It was about 25 feet long and its stride would have been as much as 9 feet on the run. It looks like it could really, really move.''
Sereno said Deltadromeus would have been two or three times as large as the similarly agile Velociraptor that evolved in Mongolia (and was made famous in the movie ``Jurassic Park'').
By the time these two predators lived in Africa about 90 million years ago, Earth's land had become a patchwork of isolated continents. The single supercontinent in existence when dinosaurs first appeared 230 million years ago divided into northern and southern land masses, Laurasia and Gondwana, respectively, about 150 million years ago, toward the end of the Jurassic period.
A further breakup occurred in the Cretaceous period, as today's continents took shape and drifted their separate ways after 100 million years ago. Until then, the various kinds of dinosaurs had been a global phenomenon, with species in one part of the world showing remarkably close kinship with those elsewhere. But the drifting continents ended this faunal exchange, isolating dinosaurs and leading to their evolution into increasingly divergent forms before their extinction 65 million years ago.
The new discoveries, Sereno said, should give scientists a ``new understanding of how dinosaurs came to be divided geographically and how that affected their evolution in the late Cretaceous.''
Sereno and an international team of colleagues reported the findings in the issue of the journal Science being published today. He also described them and displayed casts of the fossils at a news conference in Washington on Thursday at the National Geographic Society, a sponsor of the expedition.
In an accompanying article in Science, Dr. Phillip Currie, a dinosaur specialist at the Tyrrell Museum of Paleontology in Drumheller, Alberta, praised the discoveries and said they ``are changing our rapidly evolving concepts of paleogeography during the Cretaceous.''
Dr. Mark A. Norell, a paleontologist at the American Museum of Natural History in New York City, said that the fossils were important because so little had been known of African dinosaurs in the Cretaceous period and that they showed that large predatory dinosaurs lived on all the continents in that period. They had evolved in different ways, but they were superficially and functionally very much like one another and probably stemmed from distant common Jurassic ancestors.
``Now we need to know more about the relationships of these predatory animals,'' Norell said.
The new discoveries were made in the Kem Kem region of Morocco, a hot, dry land of red sandstone near the border with Algeria and in sight of the Atlas Mountains. Sereno, 38, had already established himself as one of the most successful dinosaur hunters in the field, having made sensational discoveries in Argentina, China and elsewhere in Africa. He had determined that in the time of the dinosaurs this region of the Sahara was a vast flood plain with rivers edged by coniferous trees, and he hoped that it would be rich in fossils from that period.
Sereno found the skull and 5-inch-long teeth of Carcharodontosaurus embedded in a sandstone cliff. After further analysis, the team identified the species and recognized that it bore resemblances to Acrocanthosaurus, a huge meat-eating allosauroid that lived in North America during the early Cretaceous period. This indicated that some connecting land bridges must have still existed between the northern and southern land masses at that time.
The size of the new specimen led Sereno and his colleagues to believe the African predator had dethroned Tyrannosaurus as the king of the predators. But a few weeks later, in September 1995, paleontologists announced the discovery of what may be an even larger predator, Giganotosaurus carolinni, in Argentina.
It was ``amazing,'' Sereno said, to see that predators in such widespread lands should independently reach such huge sizes.
Gabrielle Lyon, a team member who once studied at the University of Chicago, literally stumbled on the bones of what proved to be the Deltadromeus skeleton. A close examination revealed that this animal bore similarities to coelurosaurs, which ranged from birdlike creatures to Tyrannosaurus. Deltadromeus most closely resembled the smaller Ornitholestes, an agile, 6-foot-long predator found in the northern continents.
Currie said the discoveries showed clearly that many families of dinosaurs from around the world ``were free to intermix well into the Cretaceous.'' MEMO: This story was compiled from reports by The New York Times, The
Associated Press and Newsday. ILLUSTRATION: ASSOCIATED PRESS color photo
Dr. Paul Sereno lies in the 5-foot model of the Carcharodontosaurus
saharicus skull he found.
by CNB