Natural Science Forum / Biology / Paleontology / May 2005

May 4, 2005
Dinosaur 'Missing Link' Found in Utah
By Guy Gugliotta
Washington Post Staff Writer

Digging in the badlands of east central Utah on a tip from a repentant
poacher, researchers have unearthed the fossil remains of a dinosaur
"missing link" -- a primitive plant-eater that had recently evolved
from the carnivorous raptors that also produced modern birds.

The long-tailed dinosaur ate plants but had the big-bellied body of a
meat-eater gone to seed, a made-to-order victim for any passing
marauder -- except for the powerful, ropy arms and the four-inch talons
on the ends of its forepaws.

"They probably used the claws for self-defense," said Utah state
paleontologist James I. Kirkland. "Or maybe they were herding animals
who just hung out together and hoped the predators would eat someone
else."

The discovery of Falcarius utahensis, or "sickle-maker from Utah," so
named because of the claws, supports earlier research linking the
plant-eating dinosaurs known as therizinosaurs to the raptors, but also
opens the possibility that therizinosaurs may have originated in North
America rather than Asia, as previous evidence had suggested.

The findings are being reported in the Thursday edition of the journal
Nature.

"It's an extremely significant find," said Matthew Lamanna, a
paleontologist at the Carnegie Museum of Natural History who was not a
member of the Utah team. "Before this discovery, the oldest known
animal recognized as a therizinosaur came from China, and this one is
just as old and seems to be more primitive anatomically. It appears to
be the final piece of the puzzle."

Kirkland said in a telephone interview that he first became aware of
Falcarius in 1999, when colleagues showed him a box of bone fragments
they had bought at a fossil show in Tucson, Ariz. The bones supposedly
came from "private land," Kirkland said. It is illegal to excavate
fossils on public land without a permit.

Kirkland said he tried "over a number of years" to ascertain the
location of the site and finally got directions from an acquaintance of
the excavator. When Kirkland still couldn't find it, Lawrence Walker,
anxious to see his discovery properly recognized, admitted his role and
guided him in.

In rugged country about 140 miles southeast of Salt Lake City, Kirkland
found the jumbled remains of "hundreds, perhaps thousands" of Falcarius
embedded in a two-acre stretch of pebbly, 120-million year old mudstone
on a mesa top once washed by the waters of an ancient spring.

"Ninety-nine percent of the bones were the same animal," Kirkland said,
but the site offered few clues about how so many Falcarius died
suddenly in the same place. "Personally, I favor poison," he said,
either from botulism from dead animals in the water, or "some kind of
microbial bloom." The spring might also have belched a cloud of carbon
dioxide, methane or sulfur dioxide, asphyxiating the herd.

"It was pretty exciting," Kirkland recalled. He turned to Walker,
warning him "that I wasn't going to call the FBI, but if they call me
up, I'll have to tell them." Sure enough, federal agents approached
Kirkland as soon as he asked for a permit.

Walker eventually pleaded guilty to theft of government property, paid
a $15,000 fine and spent five months in prison.

Kirkland's team began excavating in 2001. Falcarius measured about 12
feet from the tip of a long neck to the end of a long tail. Like
raptors, it stood upright and had the powerful hind legs of a running,
carnivorous predator. But its teeth were tiny and leaf-shaped, designed
for shredding forage, and it had an atypically wide pelvis capable of
supporting the large gut needed to digest vegetation. And the back legs
were slightly bowed and thickened, suggesting a more sedentary
lifestyle.

"It looks like a long-necked raptor," said team member Scott Sampson,
curator of vertebrate paleontology at the University of Utah's Utah
Museum of Natural History. "We're not saying it's a vegan. Maybe an
omnivore."

The key features were the arms and claws, more powerful than those of
many raptors, but not big or blocky enough to support a large,
plant-eating quadruped.

"The claws look like blades on a scythe," said Lamanna. "They could
swing their arms with quite a bit of force."

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http://www.nature.com/news/2005/050502/full/050502-3.html