More than 30 kinds of titanosaurs have been identified. Yet how they were related and what they looked like has been difficult to figure out because until now no one had found a complete skull or skeleton.
"Since the first titanosaur was found a hundred years ago, we've had no idea of their anatomy," said Curry Rogers. "The most important thing about this discovery is that it gives us our first idea of what a titanosaur looked like from head to tail."
The researchers named the new dinosaur species Rapetosaurus krausei.
The first part of the name, Forster explained, comes from the Malagasy word "Rapeto." It's the name of a mischievous, mythical giant of Madagascara figure somewhat like Paul Bunyan, a giant woodcutter in American folklore. "Since this new species is one of the dinosaur giants, we thought the name was fitting," she said. The second word in the scientific name was chosen in honor of expedition leader Krause.
The young dinosaur measured eight meters (26 feet) long from head to tail and "probably weighed about as much as an elephant," Curry Rogers said. Because it was a juvenile, she noted, it was only about half the size of an adult titanosaur. Fully grown, a titanosaur would be about 15 meters (50 feet).
Sketching a picture of what Rapetosaurus may have looked like, the two researchers said it had a very long neck, a short tail, and a long, narrow snout. The two new skulls show that the nostrils were on top of its head, rather than at the sides of its snout, like in horses and dogs.
The teeth of Rapetosaurus were "pencil-like pegs," Curry Rogers said. "It's teeth were okay for raking leaves off trees, but it can't crunch and wasn't a very efficient eater," she explained.
The new dinosaur bones are remarkable not only because of what they reveal, Curry Rogers noted, but because they are in excellent shape despite being porous and having been buried for as long as 65 to 70 million years.
The bones of the skeleton have not been reassembled but are now being stored in museum drawers for additional analysis. Curry Rogers said an exhibit of the fossils is being planned.
Major Clues in Evolution
According to Krause, the first bone of Rapetosaurus was found in 1993, after he and a team began exploring at a site near the Madagascar port city of Mahajanga.
That bone and the others that followed were part of a dazzling array of fossils that Krause and researchers from Stony Brook, Universit d'Antananarivo in Madagascar, and several other institutions have unearthed on the island since 1993fishes, frogs, turtles, snakes, crocodiles, birds, and mammals.
Included among the fossils were the partial remains of two other dinosaur species besides Rapetosaurus that are also new to science.
"We've been fortunate enough to make one fantastic discovery after another, including some of the most complete and exquisitely preserved dinosaur material in the world," Krause said.
"The discovery of [Rapetosaurus] is just one example," he said. "It's been a fantastic ride."
Krause said he first went to Madagascar because he had long been curious about the island's "bizarre modern flora and fauna and where it came from" millions of years ago. The island has many species found nowhere else in the world.
After reading that some French military men had found assorted fossils in Madagascar in 1895, Krause organized a team to explore the area. "I thought there was the potential for the discovery of more [fossil] material," he said, adding that he was particularly interested in mammals, his area of specialty.
Within 20 minutes after they arrived in Madagascar and began digging, the team found a mammal fossil. "Then we didn't find another one for the rest of the six weeks that we were there that year," Krause said.
But that initial fossil excited him and his colleagues because it indicated that mammalsand perhaps dinosaurslived on Madagascar in the Late Cretaceous, 65 to 70 million years ago.
Previously, scientists had speculated that Africa, Madagascar, and other southern landmasses were relatively isolated during the 35 million years of the Late Cretaceous period and therefore had no dinosaurs like those that lived in other regions of the world at about the same time.
The first significant dinosaur discovery by Krause and his colleagues, which came in 1996, challenged that idea.
They uncovered the well-preserved skull of a giant meat-eating theropod, named Majungatholus. Its features resembled those of dinosaur fossils found in present-day Argentina and India. This suggests that Madagascar may not have been long isolated but connected to South America by a land bridge, perhaps through Antarctica.
Krause just made another discovery in Madagascar that will add to that debate. Also in the August 2 issue of Nature, he reported finding a tooth in Late Cretaceous rocks that provides the first evidence of an ancient marsupial in Madagascar. It's intriguing because all of the island's mammals today are placental, and marsupials are thought to have originated in the Northern Hemisphere.
Meanwhile, the skull and skeleton of Rapetosaurus will help scientists better understand the links between different groups of titanosaurs and how they're related to other sauropods.
Paleontologists had speculated, for example, that titanosaurs were closely related to Brachiosaurus. The Rapetosaurus fossils confirm that close relationship.
The National Geographic Society has funded part of the research in Madagascar. Additional support has been provided by the National Science Foundation, The Dinosaur Society, and the Field Museum of Natural History in Chicago.
This story will be aired in the United States on August 1 on the television news show National Geographic Today.
Recent National Geographic News stories on dinosaurs:
"Tidal Giant" Roamed Coastal Swamps of Ancient Africa
"Feathered" Fossil Bolsters Changing Image of Dinosaurs
Oddly Angled Teeth Make Masiakasaurus Stick Out
Additional dinosaur resources from National Geographic:
Paul Sereno: NG Explorer-in-Residence and dinosaur hunter
Destinations: Dinosaur National Monument
Educational Video: Dinosaurs on Earth: Then and Now
Children's Pop-up Book: Dinosaur Babies
Related lesson plan
Use this National Geographic News article in your classroom with the Xpeditions lesson plan: Physical Characteristics of Places: The Fossil Record
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