New Clues Aid Dinosaur Researchers
Titanosaurs, the creatures that apparently laid the eggs in Auca Mahuida, hold much mystery for scientists. But recent findings on three continents may help clarify our view of the placid plant-eaters.
They are the least understood of the sauropods, a kind of dinosaur that had four elephantlike legs, a long tapering tail, and an extended neck that held up a relatively small head. The creature most people know as brontosaurus, for example, was a type of sauropod.
Titanosaurs survived to the last gasp of the dinosaur age _ the only sauropods to make it that far _ and they left bones in Argentina, Brazil, India, Malawi, Utah and Texas, among other places. But nobody has reported finding a complete skeleton, and no titanosaur skulls have been firmly identified either.
So scientists wonder: What did titanosaur heads and feet look like? How long were the tails? How much bony armor did they have?
Beyond wanting to know what they looked like, scientists also want to know where they came from and why they survived so long.
One reason so few titanosaur remains have been found is that they just weren’t built to last. The head, for example, was linked to the neck by a small joint, which gave great flexibility. But when a sauropod died in a river _ a fate that could preserve bones under layers of sediment _ the skull tended to snap off and disappear downstream.
Since titanosaurs are best identified by tailbones, these wayward skulls lost their IDs. And it’s not enough to find a skull in the vicinity of titanosaur bones. Most titanosaur finds so far have been jumbles, with no guarantee that a particular skull bone came from the same individual as a particular tailbone, for example.
``It drives you crazy,″ says Brian Curtice, adjunct curator at the Mesa Southwest Museum in Arizona. It’s like ``two jigsaw puzzles dumped into one box, 90 percent of the pieces thrown in the trash can, and both pictures happen to be the same shade of blue.″
What’s more, skulls fall apart in the ground because their bones don’t fuse in life. The feet fall apart too, making them hard to reconstruct. So scientists don’t yet know whether titanosaurs had a claw on a thumblike digit on each front foot, as most other sauropods did.
But recent discoveries, not yet published in scientific journals, are raising hopes for learning more about titanosaurs.
``We’re finally getting a sense of what these animals looked like,″ says Scott Sampson, an assistant anatomy professor at the New York College of Osteopathic Medicine in Old Westbury, N.Y. He recently participated in several expeditions in Madagascar.
One key discovery, from Argentina, is a nearly complete titanosaur skeleton. Curtice calls it ``the best sauropod find in the 1990s, bar none.″
The skeleton, missing only back limbs, lies encased in plaster in a museum at Rincon de los Sauces in Patagonia. Found nearby in 1996, it required nearly three weeks of excavation by museum workers from Argentina’s National University of Comahue. Jorge Calvo, a paleontologist at both museums, is uncertain when it will be fully analyzed. Unfortunately, the head is poorly preserved.
Meanwhile, Sampson says, discoveries in Madagascar may include up to 90 percent of a skeleton from a single titanosaur, more complete than any reported. And a partial skull from Madagascar gives new hints of what a titanosaur’s face looked like, he says.
Still another discovery, in Utah, is challenging the conventional idea about where titanosaurs first appeared.
Many scientists believe they arose south of the equator and migrated north. The Southern Hemisphere has produced far more titanosaur fossils, and those from Africa and South America _ joined when titanosaurs first appeared _ were much older than those in North America.
Malawisaurus, the oldest titanosaur definitely identified in Africa, dates back 100 million to 140 million years. The oldest from South America, Andesaurus delgadoi, is about 100 million years old. North America’s Alamosaurus is a mere 70 million years old.
But a quarry near Moab, Utah, has now produced titanosaur remains from somewhere between 100 million and 150 million years ago, says Brooks Britt, director of Eccles Dinosaur Park and Museum in Ogden. That places titanosaurs in North America earlier than in South America and maybe about the same time as they roamed in Africa.
Britt expects the spate of recent discoveries from around the world to change a lot of ideas about titanosaurs in the next three years.
``Everybody is going to contribute the data,″ he says, ``and then we’ll go back and test our theories.″