Photo Courtesy Ewan Wolff
Ewan Wolff holds a crocodile displayed at the annual
conference of the Wildlife
Disease Association. The conference was held in Australia where crocodiles are raised for meat and leather.
"There's a lot of stuff you can
read about, but it's a lot more useful to actually see what they do."
DEAD COWS, LIVE CROCS REVEAL DINOSAUR SECRETS
by Evelyn Boswell
Frankie Jackson and David Varricchio followed a trail of rotting cows to see how a river deals with the unsuspecting animals it traps. Ewan Wolff called on thousands of Australian crocodiles to find family resemblances to extinct cousins. Mary Higby Schweitzer retrieved a decaying ostrich from the back of a South Carolina barn and peered inside its leg bones. Scientists who investigate animals that have been dead for 65 million years sometimes look for clues among the living or at least the more recently deceased, said Montana State University paleontologists who have dug and mapped dinosaur remains all over the world.
Jackson and Varricchio are among the MSU scientists who have turned to more modern animals in their quest to understand dinosaurs. Wolff, an MSU graduate student, and Schweitzer, a former MSU graduate student, do the same.
“The simultaneous drowning of these cows provided a unique opportunity to examine the consequences of mass death within a fluvial system,” Varricchio said about some 40 cows that died last year after breaking through the ice on the Yellowstone River north of Glendive.
“These cows attempted to cross the frozen edge of the river to drink at a still open stretch,” Varricchio explained in a paper he presented to the Society of Vertebrate Paleontology in October. “The herd broke through the ice, drowned and became entrapped beneath the ice. Here they remained for over a month until the spring melt, when the river, freed of its ice jam, distributed the carcasses downstream.”
Varricchio and Jackson realized the potential of the incident that occurred near the end of the 2003-04 winter, so canoed down the Yellowstone River in May 2004 to see if they could find any remains. Successful even during the high waters of paddlefish season, the paleontologists returned two weeks later with students who were attending MSU’s paleontology field course in Glendive. They made a third trip in September 2004, a fourth in May 2005 and a fifth this September.
“Catastrophic mass drownings have been inferred for a wide variety of vertebrates from titanotheres to hadrosaur dinosaurs, but relatively little modern data exists for comparison,” Varricchio said.
Varricchio and Jackson found 33 cows spread over 25 miles when they first canoed the river. Nearly all were intact and severely bloated. Several had unborn calves. The paleontologists found groups of two to five cows as far downstream as 18 miles.
By late September 2004, Varricchio and Jackson found only 17 carcasses, but some of them remained in groups. The most complete carcasses were held together with stiff upper skins, raising the possibility of someday finding dinosaur “mummies,” Varricchio said. Skulls were relatively scarce, but ribs and shoulder blades were unexpectedly plentiful.
The discovery of groups was important, Varricchio said, because dinosaur bones have been found that way. It supports the theory that mass deaths may have been responsible.
Wolff, Varricchio’s graduate student, normally focuses on wounds and lesions in dinosaur jaws and traveled to Australia this year to present his research at the annual conference of the Wildlife Disease Association. In his spare time, though, he observed emus, turtles, lizards, marsupials and cassowaries to see what the primitive animals and birds could teach him about dinosaurs.
He also dropped by crocodile farms and zoos and studied crocodiles in the wild. He photographed crocodile homes and the belly marks they left by sliding down muddy river banks. He consulted veterinarians who treat crocodiles in captivity or encounter them in nature.
“There’s a lot of stuff you can read about, but it’s a lot more useful to actually see what they do,” said Wolff who noted that Australians raise crocodiles for meat and leather, so it seemed logical to investigate the animals while he was in the country. He observed crocodile personalities, their injuries and wounds. He gained new perspectives by watching crocodiles eat, move, sleep and snap.
He noticed, among other things, that a crocodile’s life isn’t always dramatic. It was probably the same for dinosaurs, Wolff said. Just because a paleontologist finds a punctured dinosaur jaw doesn’t necessarily mean it resulted from a fierce battle, for example. The dinosaur could have hurt himself by ramming into a tree or chewing a rib. In the same way, most of the infections Wolff saw in crocodiles had more to do with diet than injuries. Perhaps it was that way with dinosaurs.
Schweitzer, now a paleontologist at North Carolina State University and the North Carolina Museum of Natural Sciences, said she knew as soon as she opened a box of bone fragments that she was looking at a female dinosaur. She had examined enough bird bones and knew enough about bird biology to recognize the medullary tissue that lines the inside of bone marrow cavities when birds are laying eggs.
She often looks at ostrich and emus, because they are primitive birds that have more in common with dinosaurs than more advanced birds like robins, Schweitzer said. To find the ostrich whose bones she compared to B. rex, she searched the Internet for an emu and ostrich owner site. Then she asked if anyone had birds that died recently during an egg-laying cycle. The outcome was a call from a South Carolina farmer and a decomposing ostrich that yielded the same kind of tissue she saw in B. rex.
Once again, a dinosaur relative had come to the aid of a dinosaur researcher.