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Morocco theropods
Headline News just ran--and has probably been running for most of this
morning and perhaps yesterday--a fairly long item on Paul Sereno (name
misspelled Paul Soreno!), the University of Chicago, and their two
newly described theropods. The theropods were featured in the two-part
Paleoworld show that opened the current season last fall and one of
Sereno's talks at the 1995 SVP in Pittsburgh. So--I went to the New
York Times news column on AOL, and bingo: found the following item,
which I'm transmitting herewith. I presume this will not only appear
in today's SCIENCE but will also be in Newsweek, Time, etc. Watch for
it.
May 17, 1996
By JOHN NOBLE WILFORD
c.1996 N.Y. Times News Service
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 on Thursday.
By the time these two predators lived in Africa some 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 on
Friday. 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 in an interview.
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 this region of the Sahara was a vast
flood plain with rivers edged by coniferous trees in the time of the
dinosaurs, and he hoped that it would be rich in fossils from that
period.
Sereno found the skull and five-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, six-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."
Copyright 1996 The New York Times