March 19, 2002
In Search of the Lost Link
to Archaeopteryx
Clark Continues His Quest In Search of Bird Origins
By Thomas
Kohout
In the heart of an inhospitable
land where August temperatures soar past 110 degrees, James Clark, the
Ronald B. Weintraub Associate Professor of Biology, led a small expedition
in search of the origins of birds. A group of 12 paleontologists, guides,
and graduate students made their home in a dusty region of Northern
China, better known for its role in the 2001 movie, “Crouching
Tiger, Hidden Dragon” than as the final resting place of a predecessor
of the reputed missing link between dinosaurs and birds.
Filling in the Family Tree
Clark came to the University
seven years ago through an endowed professorship from Ronald Weintraub
to advance the study of systematics, a theoretical approach to comparative
biology. Through systematics, scientists compare different species in
order to better understand the evolutionary origins of life.
The effort to extend the link
between dinosaurs and birds is still a contentious one, according to
Clark, despite the mounting evidence. He says it’s a controversial
issue only because two or three scientists have decided to argue in
the face of 100 years of evidence.
“Scientifically it’s
a no-brainer,” says Clark. “It’s just surprising that
these people don’t want to accept that birds evolved from dinosaurs.
Even with this spectacular record of dinosaurs with feathers… I
don’t know what these people want to see.”
Systematics seeks to trace
the pattern of evolution among species, studying how things are related
to one another, looking at the different features the species have,
and examining the evolution of those features. From features such as
the feathers found in archaeopteryx fossils, scientists determined that
dinosaurs developed feathers long before they learned to fly, and thus
feathers first evolved for something other than flight.
“We’re taking this
information we’ve gained from feathered dinosaurs, what you can
learn about their skin and the epidermal structures, and tracing that
on the evolutionary tree,” explains Clark. “That’s the
primary focus of our research.”
Feathers are an obvious example,
Clark explains, but there are other features paleontologists look for
such as feeding systems or the ear region. On a previous expeditionary
team, Clark was particularly fortunate, uncovering evidence of a previously
unknown behavioral trait.
Each summer since 1991, Clark
has joined colleagues from the American Museum of Natural History in
New York to explore the southern Mongolian portion of the Gobi Desert.
Those expeditions yielded a startling cache of fossilized dinosaur bones,
and changed the way paleontologists think about some of the species.
The museum expedition found
nesting dinosaurs — the fossil remains of veloco-raptors sitting
on top of their eggs the way birds incubate their offspring.
“That’s a very characteristic
feature of bird behavior that is not found in other vertebrates,”
explains Clark. “Crocodiles and lizards, for instance, don’t
have that characteristic.”
According to Clark, depending
upon the fossil specimens they find, they could explain how archaeopteryx
splintered from the family tree to eventually evolve into a bird.
“Depending upon what you
find,” he says, “it’s going to fit into one of these
groups or it’s going to change something about how you perceive
those groups. But it’s always unexpected what exactly you’re
going to find.”
A Pinch to Grow On
It’s that uncertainty,
says Clark, that makes paleontology exhilarating and utterly frustrating.
Before scientists can embark on their quests for fossils, they must
find the funding for the expeditions.
“You can’t say, ‘I’m
going to go look for dinosaurs, but I’m not sure exactly what I’ll
find,’ ” Clark laments.
Fortunately, GW’s facilitating
fund provided Clark with the luxury of spending the summer of 2000 scouting
places in the Chinese portion of the Gobi Desert. Clark was joined by
Professor Ghao, a Chinese paleontologist who had been collecting dinosaurs
in the area for years, to aid in the search.
Ghao led Clark to several sites that had been explored previously, as
well as some where he believed nobody had searched before. Because of
the exploratory nature of the trip, the group had time to gauge how
much exposed rock was available at the various sites, how many observable
fossils there were, and how likely each site would continue to be productive.
That information helped Clark obtain a grant from National Geographic,
which funded the trip last August.
“It’s very hard to
apply for big grants for field projects until you’ve published
something and you have a good track record,” Clark says. “Groups
generally don’t fund exploratory work. So National Geographic was
very good to us. They will fund you for field research to find fossils
and you can develop that and then apply for these larger grants.”
A Place to Call Their Own
While Clark’s work with
the American Museum of Natural History in Mongolia has been tremendously
successful, the project was never really his. He longed to have more
influence and authority.
“For
several years I’ve been trying to start a program that wasn’t
run by someone else,” Clark explains. “I haven’t been
able to always include my students in my projects because it’s
run through the museum.”
This time he was able to bring
Brian Andres, who is writing his master’s thesis on the pterodactyl
— a flying reptile from the feathered dinosaur age.
With the help of the facilitating fund, Clark found what he was looking
for. He chose an area called Wucaiwan in the Xin Jiang (pronounced Shin
Jang) province, a semi-autonomous region in China along a stretch of
the old Silk Road.
Dinosaur fossils had been discovered
in the Xin Jiang area in the 1920s, when motor vehicles were first opening
the wilds of the Asian landscape to western explorers. A Swedish explorer
named Sven Hedin, explored that part of the Gobi Desert in the early
1930s. Hedin led a team of scientists around the Gobi, including Xin
Jiang, and those expeditions were the first to find fossils in the area.
As a partner in the expedition,
Clark chose a rising star among Chinese paleontologists, Xu Xing (pronounced
Shoo Shing).
Xing has been uncovering feathered
dinosaurs in eastern China, in what used to be Manchuria in the province
of Liao Ling, where Clark says many spectacular fossils have been unearthed.
“These are dinosaurs that
have soft tissue preservation, so you get skin and the skin happened
to be covered with feathers. These are some of the most spectacular
things coming out of China now.”
Xing has been one of the two
or three primary people working on these feathered dinosaurs in China.
He has several publications in Nature, even though he has yet to earn
his PhD.
The area where Xing has found
these fossils is not the best site for striking out on your own, says
Clark. “They are quarried out of these great pits and the local
farmers are out in huge numbers quarrying this shale to get the specimens
they are then selling to scientists. Or if they are sneaky, they sell
them to foreign bone collectors.”
Even though it is illegal to
do that, the monetary incentive is pretty high and the fossils attract
a huge number of farmers. Consequently, Xing, too, was interested in
finding a site to call his own.
His contribution to the team
was particularly helpful when handling the necessary government permits
and paper work to get the expedition approved. The local level, however,
was trickier. Because Xin Jiang is semi-autonomous, the local people
don’t even want the people from Beijing to come in.
“We made arrangements
with them,” says Clark, “by offering to help them set up their
own museum. They are collecting their own big dinosaur, and the people
from Beijing are helping them set up a museum. It’s worked out
very nicely.”
Why the Gobi?
“We were more interested
in these fossil beds in Xin Jiang,” says Clark, “because after
the 1920s when fossils were found there, nobody spent much time there
until the 1980s.
“Our main focus isn’t
on the big dinosaurs, it’s on the smaller dinosaurs, which you
can get a much larger variety of.”
Clark set out to find small
carnivorous dinosaurs related to birds, but that predate the oldest
bird-like fossil, archaeopteryx. They hoped to find a number of the
specimens that should be there, but had yet to be found. Clark explains
there is a practical explanation — people want to find big skeletons
for their exhibits in museums and it’s just harder to spot the
smaller fossils.
“I have a lot of experience
finding small fossils; it’s the main emphasis of my field work.”
Boning Up
“We found four specimens,”
says Clark, adding the best fossil was a member of one of these later
groups of small carnivorous dinosaurs — what some have called the
ostrich dinosaurs, Ornithosuchus — that they were expecting to
find. “We can’t really study them until we get them out of
the rock, but we saw enough of the skeleton in the rock to tell that
at least one of them was a member of the group we were looking for.
”
Once Clark and his colleagues
clean the fossils, they’ll submit papers to various journals such
as Nature. Until they extract the bones from the rock, however, they
can’t be sure exactly what they came back with.
“We would have been happy
with two or three good skeletons, but we found at least five good skeletons
that are nearly complete. We have 12 good specimens where we have more
than a dozen bones or so. We also found a lot of other different animals.
We have about 40 total.”
Send feedback to: bygeorge@gwu.edu
