Digging Dinosaurs -- How scientists put the pieces together
February 1, 2004
Books and movies have created in the public mind vivid images of what dinosaur hunters do. In some cases, fiction approaches the reality, but seldom does it do justice to the physical labor in the harshest conditions and painstaking intellectual rigor that goes into finding and interpreting dinosaur remains.
When Judd Case, a professor of biology at Saint Mary's College of California, and James E. Martin, curator of vertebrate paleontology at the South Dakota School of Mines & Technology, stumbled across what they believe are the fossilized remains of a new dinosaur species on the Antarctic Peninsula, they quickly put the pieces together in their heads. Years of education, training and experience enabled them to recognize and make sense out of what others might have ignored.
But spotting fossil remains is only a first step in accurately recreating a creature that has been dead for many millions of years. Confirming it, categorizing it and eventually concluding you've found something new requires far more than the ability to recognize an ancient bone lying on a frozen beach.
Case and Martin boarded the Laurence M. Gould, the National Science Foundation's polar research vessel in late November of 2003, expecting to return to Vega Island off the Antarctic Peninsula, the portion of the continent that juts northward toward South America. There, several years earlier, they had found the remains of a hadrosaur, or duck-billed dinosaur, during a joint U.S. and Argentine expedition.
But a return to Vega Island was not to be. Ice conditions would not allow the inflatable boats to ferry the researchers from the ship to land on shore. "We weren't able to get where we knew fossils would be," said Martin. "The only possible place left to do anything was James Ross Island."
Even then, they were forced to camp at a spot six kilometers (four miles) away from a peninsula called the Naze, where Martin hoped to find remains not of dinosaurs but of marine reptiles such as plesiosaurs, on which he is an expert. "That in itself was interesting," Martin remarked of the regular hikes across shore ice, "because some days our trail would have floated away."
Except on the occasional sunny day, the team worked in snowy whiteouts and other poor weather reminiscent of conditions endured by the shipwrecked crew of Sir Ernest Shackleton's vessel Endurance, who were stranded not far from the fossil expedition.
Their spirits, Martin conceded, were at low ebb.
"I was probably happier than Judd was, because I thought 'At least we 'll get some good marine reptiles'," he said. "But, absolutely, we really were not doing well at all. We'd spent a lot of money and time and all we'd found was a marine vertebrae."
Then, on Dec. 12, 2003 everything changed.
Case almost literally stumbled across something that didn't seem to fit in with the other finds the team was making.
"I had worked myself away from the main group and was following up a slope. I started to see a lot of golf-ball sized rocks that were round and smooth," he said.
The stones likely were rocks marine reptiles swallowed to digest their prey, similar to the stones found in the gizzards of modern birds. In death, the stones would have settled on an ancient ocean bottom in the animal's corpse.
"Expecting to run into marine-reptile bones, I came across a bone that represented something quite different. It had rounded ends and a groove on it," Case said. "I didn't think it was from a marine reptile because of what I've learned from Jim. I didn't think this is what a marine reptile looks like."
Case then showed his find to Martin, expecting to be convinced they were bones of an extinct ocean creature. "Jim is very good at being skeptical," he noted.
Case, Martin and their colleagues pored over the bone, trying, in a sense, to make its characteristics fit into their preconceived notions.
"We knew we working in what were once relatively deep marine waters. And we were trying to make it into everything that might be marine reptile," Martin said. "Initially, we were trying to make it anything but a dinosaur."
But as the research team scoured a roughly 40-square-meter (50-square-yard) area, finding a tooth here and a jawbone there, they became convinced the animal they were reconstructing was, in fact, a dinosaur.
"We just kept going and going until we couldn't find anything more. Until we felt we had really covered the area," Martin said.
And, gradually, accumulated evidence showed the dinosaur was a predator.
"As we began to find more pieces throughout that afternoon, Jim said 'you know, I've only seen these things in meat-eating therapods'," or "beast-footed" dinosaurs, like Tyrannosaurus rex and smaller carnivores.
Having found all the pieces they could, including portions of the animal's legs and feet as well as teeth and jawbones, both Case and Martin tentatively agreed they had found the remains of a meat-eating dinosaur, although "everything was working against that conclusion," Martin noted.
The location, for example, would have been covered in fairly deep water when the creature was alive. They later theorized that the animal's body floated out to sea after it died.
Also, at the apex of the food chain and representing a very small percentage of living creatures, predators in nature are less likely to leave any physical trace of their passing.
According to Martin, "the skeleton appears to have been eroded out from some time. Every bone we collected was broken."
On the island the researchers had already moved from the collecting stage of their investigation to analysis, trying to confirm what they reluctantly believed was true.
"In some cases, we sat down early with all the bones spread out, began to put things together that looked like they belonged together," Case said.
They also referred to figures in a book that happened to be in camp. "The photos helped us to identify some of the bones," he said.
Martin notes that even though the bones they found were fragmentary -- "This wasn't 'Jurassic Park,' where they blew the dust off that complete skeleton" -- the evidence was sufficient to make a serious analysis. "We got the two best ends of the animal for identification: the head and feet. In this case, foot bones, claws, and teeth."
Later, aboard ship and headed back to the United States, the scientists laid the bones out on a large piece of paper in one of the ship's labs in the positions they would have held in life. They were beginning to answer a question even larger than whether the creature was a dinosaur: "Is it just new to the region or is it new to science?" Case noted.
The answer lay not, as one might expect, in 21st-century scientific tools such as DNA analysis, because, Case notes, "the genetic material that one would use for such a comparison is all gone," turned to stone like the bones themselves.
Instead, a more venerable method was used to decide they had found something never before seen by science -- searching the literature in specialized repositories, such as, in this case, the one at University of California, Berkeley, and comparing the physical evidence they had with characteristics of specimens that had already been described. They made comparisons between their partial skeleton and those of animals from the three known major groups of meat-eating dinosaurs.
"You get more and more specific about 'where does this best fit', but you've got to start with the major categories first," Case said. "The vast majority of the bones we're finding are from the lower legs, the ankles and the feet. So then you can say 'If you have this suite of bones, you belong this group." We could begin to eliminate groups that way."
"The group it seems to fit in best is one held together by their general primitive therapod characteristics," he added.
Eventually, Case, Martin and their team were certain they had found a new creature, previously unknown to science.
But as is often the case in scientific research, new-found answers brought new questions. Questions that likely will have to wait for another day, and perhaps a different expedition, to answer.
"One of the surprising things is that animals with these more primitive characteristic generally haven't survived as long elsewhere as they have in Antarctica," Case said. "For whatever reason, they are still hanging out on the Antarctic continent. Why is this group still here when in other places other groups have displaced them? We don't know."
Peter West, NSF, (703) 292-8070, email@example.com
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