Thursday, July 12, 2007
"Tidal Giant" Roamed Coastal Swamps of Ancient Africa
"Tidal Giant" Roamed Coastal Swamps of Ancient Africa
By John Roach
for National Geographic News
May 31, 2001
Researchers have unearthed fossils of what appears to have been the second largest known creature ever to walk on Earth. The dinosaur, named Paralititan stromeri weighed in at an estimated 75 tons and measured as long as 100 feet (30.5 meters).
It dwelled 94 million years ago in mangrove swamps that once covered what is now a remote desert area in western Egypt.
"It was a truly enormous dinosaur by any reckoning," said Joshua Smith, a doctoral student at the University of Pennsylvania in Philadelphia. He headed the research team that found the dinosaur fossils and is the lead author of a paper reporting on the discovery in the June 1 issue of Science.
The partial skeleton of Paralititan included an upper arm bone 1.69 meters (5.5 feet) long. By comparing it with other fossils, the scientists concluded that Paralititan was the second largest dinosaur ever found, exceeded in size only by Argentinosaurus, which lived at the same time in an area of what is now Argentina.
The bones of Paralititan were found in Egypt's Bahariya Oasis, a fossil trove that has remained largely unexplored since early in the 20th century, when German geologist Ernst Stromer discovered four smaller dinosaur species at the site. All of Stromer's fossils were destroyed in 1944 during a World War II attack on Munich by Allied forces.
Former Tropical Swamp
Smith and his colleagues believe that millions of years ago the Bahariya Oasis was a large tropical forest—probably much like the Ten Thousand Islands region of Florida's Everglades National Park, a shallow-water area of tidal flats and channels. The oasis later became desert.
The Paralititan fossils were found in fine-grained sediment full of plant remains and root casts. The researchers also found fossils of turtles, crocodiles, other large sauropods, and three carnivorous dinosaurs the size of Tyrannosaurus rex.
The researchers note in Science that these creatures thrived during a "hothouse" global climate. There was very little difference in temperature between the poles and the equator, and sea levels were high—climatic conditions apparently favorable to a population of large-bodied terrestrial herbivores, such as Paralititan.
"It is possible that the environment we found Paralititan in was among the most productive environments in the world at that time," said Kenneth Lacovara, a geologist at Drexel University in Philadelphia and co-author of the scientific paper.
The discovery of these and other large vertebrate fossils in Egypt lends credence to a theory that Africa and South America were part of the same land mass during the Late Cretaceous period (146 to 65 million years ago), said Thomas Holtz, a vertebrate paleontologist at the University of Maryland in College Park.
Scientists have found groups of vertebrates that were common to South America and Madagascar during the Late Cretaceous, but these same groups have appeared to be missing from Africa.
One possible explanation for the mysterious absence is that Africa may have split apart from South America before the Late Cretaceous. A second explanation holds that the two continents were still attached through the Late Cretaceous, but relatively few dinosaur fossils have been discovered in Africa because research in the area has been limited.
"This discovery is consistent with the second model," said Holtz, adding that Paralititan seems to be closely related to Argentinosaurus.
• A Giant Among Dinosaurs
Field researcher Matthew Lamanna helps excavate Paralititan stromeri's left humerus, which weighs 400 pounds.
Photograph courtesy of Josh B. Smith/University of Pennsylvania
Josh Smith had one goal when he set out to become a paleontologist: "I wanted to find something big that everyone else had overlooked." Last June, Smith announced he had unearthed the bones of the second largest creature known to have walked the Earth, a dinosaur that would have dwarfed four elephants standing on top of one another. The lumbering herbivore measured 80 to 100 feet long, weighed as much as 150,000 pounds, and 94 million years ago foraged in Egypt's BaharÏya Oasis, an area 160 miles southwest of Cairo. Baharõøya is now part of the Sahara Desert but was mangrove swampland during the late Cretaceous Period.
Smith dubbed his titanosaurid Paralititan stromeri. Paralititan means "tidal giant," and stromeri honors Ernst Stromer von Reichenbach, a Bavarian geologist who found four new dinosaur species in Baharõøya between 1915 and 1936. Allied bombers leveled a Munich museum in 1944 that housed the fossils and notes from Stromer's expeditions. Meanwhile, the dinosaur quarries he discovered disappeared under the swirling sands of the Sahara. For more than half a century, the Baharõøya Oasis attracted few fossil hunters. While drinking beer one night with his fellow grad students at the University of Pennsylvania, Smith decided to search for the old sites: "It sort of had the feel of an Indiana Jones adventure."
On a subsequent trip to Egypt, Smith set out across the desert in a Toyota Land Cruiser with friends. Smith was armed with geographic coordinates for an old Stromer quarry that happened to be wrong, so he was soon lost."We headed for an outcropping that looked interesting," he says, "and I stuck my head out the window just to see if I could spot anything." That's when he noticed a darkish lump protruding from the sands. "I said, 'Whoa!' Bones have a fractured look about them that rocks never do. And this was a bone for sure."
The lump turned out to be part of the forearm of Paralititan stromeri. Later, Smith and a team of researchers recovered about 20 percent of the creature's skeleton. Argentinosaurus, another titanosaurid discovered in South America in 1993, is the only known dinosaur of comparable size; it was roughly the same length as Paralititan but weighed 60,000 pounds more. Still, Smith remains modest about his success: "Paleontology is just a lot of guess-work and a lot of blind luck. It's nothing more complicated than that."
— Curtis Rist
Posted by lmurx at 4:33 PM