Two New Dinosaurs Discovered in Antarctica
for National Geographic News
|March 9, 2004|
Working in some of the planet's harshest conditions, fossil hunters have
found two completely new species of dinosaur in Antarctica. This
increases to eight the number of dinosaur species found on the
perpetually frozen southern landmass.
The discoveries, made in December, were recently revealed by the National Science Foundation, the body that coordinates U.S. research in Antarctica.
The first, a 190 million-year-old plant-eater from the early Jurassic period, was found by chance on December 713,000 feet (3,900 meters) up a mountain. A mountaineer accompanying paleontologists turned up the animal's huge pelvis in an informal search only a few miles from the South Pole.
Two thousand miles (3,200 kilometers) across the continent, and less than a week later, the scant remains of another dinosaur were foundcompletely by chanceon what once was the bottom of a shallow ocean. This 70-million-year-old dinosaur is the only known Antarctic meat-eater from the late Cretaceous period and is thought to have unusually primitive features for this period. Paleontologists had to trek 8 miles daily (13 kilometers) across treacherous ice floes to reach it.
"We don't get many opportunities to go to Antarctica and there is a short weather window of opportunity each time," said veteran dinosaur hunter Judd Case of St. Mary's College of California in Moraga. Case was on the team that made the coastal discovery. "Yet [Antarctica] consistently turns up new surprises as far as life on Earth goes," he said.
Little is known about the dinosaurs that once roamed what is now Antarctica. All fossils found so far are from the margins of coastal islands or exposed mountain rock facesthe few places free of a thick ice layer. But the continent was not always so cold.
Antarctica has sat at much the same latitude for the last hundred million years. But during the Cretaceous it enjoyed a warmer, lusher climate, similar to that of the U.S. Pacific Northwest today. (The Cretaceous period started 144 million years ago and ended 65 million years ago.)
Case, his co-worker James Martin, and their team originally set out to test a theory about the migration of extinct animals by looking for marsupial fossils on Vega Island, just off the Antarctic Peninsula (the peninsula juts towards South America).
The earliest marsupials are known to be from North America, but their later representatives, and some dinosaurs, are known to be from Australia alone. The researchers believe that animals may have migrated from the Americas, through a warmer Antarctica, and on to Australia. All three continents were likely linked by land bridges during the late Cretaceous.
However, harsh weather trapped the team's boat in ice, and they were unable to pursue their original goal, Martin said. He is a paleontologist at the South Dakota School of Mines and Technology.
Disheartened, the team stopped off on James Ross Island instead. The rocks here are made up of sediments laid down in an ancient sea. As such, the team did not expect to discover fossils of any land animals here, said Martin.
But alongside the typical clams, ammonites (dinosaur-era mollusks), and other sea life, the team started to find some more exotic fragments. Slowly the legs, feet, and portions of the jaws and teeth of a carnivorous dinosaur began to appear. The dead animal had likely been washed out to sea and had settled on the bottom of what would have been the Weddell Sea 70 million or so years ago.
Primitive Relic Fauna
Currently known as the Naze theropod, after the Naze region of the island where it was found, the coastal dinosaur is estimated to have stood just 6 to 8 feet (1.8 to 2.4 meters) tall in life. Theropods are the group of dinosaurs to which allosaurs, tyrannosaurs, and velociraptors belong. Another Antarctic therapod, a large carnosaur, is known, from the previous discovery of a single bone.
In some ways however, the newfound coastal dinosaur was very different from its late Cretaceous contemporaries. "It represents a group of dinosaurs that is rather primitive," Case said. "[The leg bones] have not been fused to the foot, as in more advanced theropods and birds." The teeth are also unusual, he said.
The dinosaurs discovered in Antarctica so far present a kind of "relic fauna," Case said, with most groups more commonly associated with other regions at earlier times.
One theory is that newly successful flowering plants were slower to colonize the Antarctic than other continentspossibly because the landmass was cloaked in total darkness for so many months of the year.
During the late Cretaceous, Antarctica was still smothered with the cycads, palms, and ginkos. In other regions these plants were more typically found during an earlier period, the Jurassic. This may explain why older dinosaur types persisted in Antarctica. (The Jurassic period started 210 million years ago and ended 144 million years ago.)
The discovery of a new sauropod from the 13,000-foot-high (4,000-meter-high) peak of Mount Kirkpatrick, near to Antarctica's Beardmore glacier, was almost as fortuitous as the coastal find.
Fossil hunter William Hammer, of Augustana College in Rock Island, Illinois, and his team, had flown hundreds of miles inland by helicopter to continue the excavation of a dinosaur they discovered there in 1991. Cryolophosaurus ellioti (an early Jurassic carnivore) was embedded in solid rock, in a site that was a soft riverbed 200 million years ago.
While Hammer's team busied themselves with the specimen in hand, mountain safety guide Peter Braddock scoured the area in a casual search for other fossils. "I jokingly said to him 'Keep your eyes down; look for weird things in the rock,'" Hammer recounted.
Braddock found something weird indeedpart of an enormous pelvis, much bigger than the corresponding bones of Cryolophosaurus.
A lot more of this animal, including much of its vertebral column (up to 3,000 pounds, or 1,400 kilograms, of fossil) is being shipped back to the U.S. for analysis. However, a preliminary investigation suggests that the sauropod would have been 6 to 7 feet (1.8 to 2.1 meters) tall and 30 feet (9 meters) in length. Dated to 190 million years old, "the new fossil is from a key time to learn about the early evolution of dinosaur groups," Hammer said.
This may be the largest dinosaur ever found in Antarctica and perhaps the oldest, he said. Even so, compared to later four-legged, plant-eating sauropods (such as brachiosaurs and Diplodocus), the new species is "kinda wimpy," Hammer said. Some sauropods may have reached a whopping 100 feet (30 meters) in length.
Antarctic dinosaurs may have been different in other ways that scientists do not yet understand, said St. Mary's College of California's Case. Some Australian dinosaurs from far southerly latitudes appear to have large eyes, useful in a nocturnal habitat, he said. Future fossil finds may offer clues as to how these animals were adapted to the six months of darkness, which still today restricts Antarctic researchers and all life in polar regions.
"I have no doubt that there is a tremendous fossil record buried under the ice sheet," Case said. "There have already been large numbers of fossil plants and animals recovered," he said, despite the fact that less than 5 per cent of the landmass is exposed for prospecting and finding fossils.
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