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Dinosaur Heart Story from NYT/AP



Here's an AP story I lifted from the New York Times
concerning this heart-rending story.

Incidentally, they also found a South Dakota driver's
license in its pocket, confirming one of my own pet
hypotheses.

                         *  *  *

By JOHN NOBLE WILFORD

The Associated Press 
 
The heart of "Willo," top, is on display at the North
Carolina Museum of Natural Sciences in Raleigh, North
Carolina. An X-ray suggests that the dinosaur may have
had a four-chambered heart typical of warm-blooded
animals, instead of the simpler reptile heart. At
bottom, the skeleton is so well preserved that
66-million-year-old tendons are visible along the
spinal column. 

There it was, they reported today, in the chest cavity
of a dinosaur's fossil skeleton uncovered in South
Dakota. Encased in a natural sarcophogus of stone, the
heart was the size of a grapefruit and had fossilized
into reddish-brown stone 66 million years ago. 

Examining the stony material with computerized imaging
technology, scientists came upon an even bigger
surprise, one that could profoundly change theories of
dinosaur physiology and the place of at least some of
these fabulous creatures in the evolutionary history
of life. Visible traces of the heart's internal
structure revealed, the discoverers said, that the
organ was more like the heart of a bird or mammal than
any known reptile. 

"It's truly amazing that this animal seems to have had
such a highly evolved heart," Dr. Dale A. Russell of
the North Carolina Museum of Natural Sciences in
Raleigh said in announcing the find. "The implications
completely floored me." 

The evidence for a four-chambered heart with a single
aorta, Dr. Russell and his colleagues concluded,
strongly suggested that this and perhaps many other
dinosaurs had higher metabolisms than other reptiles.
If this is true, they may have been warm-blooded
instead of cold-blooded like other reptiles and thus
could have engaged in more sustained activity in
foraging and fighting, in chasing prey or escaping
predators. Such advanced hearts are capable of
distributing more completely oxygenated blood
throughout the body. 

The findings also seemed to strengthen the hypothesis,
which has gained considerable support in recent years,
that some dinosaurs were ancestors of today's birds,
which are warm-blooded. 

"It's pretty surprising that they would find something
like this," said Dr. Mark A. Norell, a dinosaur
paleontologist at the American Museum of Natural
History in New York City, who was not involved in the
discovery. "It's exciting to see another set of data
to bolster our case for a close relationship between
dinosaurs and birds." 

Dr. Norell said that Dr. Russell was an experienced
dinosaur researcher with a reputation for cautious
work. But others in the field will need to evaluate
all the data from the analysis, he said, not just what
is being published now. A report of the discovery is
being published in today's issue of the journal
Science. 

"All of this will undergo critical review in the next
couple of years," Dr. Norell said of the immediate
findings and their potential implications. "We will
just have to wait and see how it shakes out." 

Dr. Paul C. Sereno, a paleontologist at the University
of Chicago, said that he and some other dinosaur
specialists had "serious reservations" about the
putative heart discovery. He questioned whether
internal organs could have been preserved in the
sediments where the specimen was found. From a study
of images of the presumed organ's interior, he further
said, it was not clear to him that the structure could
with certainty be identified as that of a heart. 

In their journal report, Dr. Russell and colleagues
urged that fossil hunters in the future make a point
of looking for traces of soft tissue in their
discoveries. Unlike teeth and bones, the tissues of
organs usually decay rapidly, before they can be
fossilized through the replacement of all organic
material with minerals. The fossil retains the
original shape and structure of the body part, if not
the original matter and its cellular structure. 

The scientists are not sure, but they suspect that
when this dinosaur died it was almost immediately
buried in waterlogged sand, perhaps the sediment
beneath a stream. Submerged in such an oxygen-poor
environment, some of the animal's tissues petrified
before decomposition set in. Previously, the only
known dinosaur internal traces were fossilized
intestines found in sediments from a former lake bed
in Italy. 

Besides Dr. Russell, who is also a professor at North
Carolina State University, the team that found and
analyzed what may be the first known dinosaur heart
included Paul E. Fisher, director of North Carolina
State's Biomedical Imaging Resource Facility and a
graduate student in paleontology; Dr. Michael
Stoskopf, a comparative anatomist, and Dr. Reese
Barrick, a paleobiologist, both at the university;
Michal Hammer, an independent fossil collector from
Oregon who found the dinosaur, and Dr. Andrew A.
Kuzmitz, a physician in Ashland, Ore., who first
examined the specimen with computerized tomography, or
C.T., imaging scans. 

The dinosaur in question was a 660-pound, 13-foot-long
plant-eating animal that lived and died not long
before the extinction of all dinosaurs, which occurred
about 65 million years ago. In 1993, Mr. Hammer found
the skeleton embedded in sandstone in Harding County,
in northwestern South Dakota. The fossils were
acquired by the North Carolina museum three years
later, where they are on display. 

The specimen has been identified as a member of the
Thescelosaurus, meaning "marvelous lizard," genus. Its
species has not been determined. For the time being,
the dinosaur usually goes by the nickname Willo, after
the wife of the rancher on whose land it was found. 

When he saw a huge lump of stone beneath the
well-preserved ribs, Mr. Hammer suspected that the
chest cavity might still hold some internal organs.
The first C. T. scan by Dr. Kuzmitz seemed to show a
heart inside the stony shell, but the two-dimensional
images left room for doubt. Then imaging specialists
at North Carolina State's College of Veterinary
Medicine used new software to produce
three-dimensional pictures. 

"Once the computer software put all the 2-D images
together into a 3-D model, it became very apparent
that, yeah, this was the real thing," Mr. Fisher said.
"You could see both ventricles and the aorta." 

The ventricles are adjacent chambers in the lower
heart. In this case, they were clearly separate by an
iron-rich wall, another clue appearing to confirm this
to be a heart. A single tubular structure resembling
an aorta led from the left ventricle. The two upper
chambers, the atria, were not distinguishable, though
the scientists felt certain of their existence when
the animal was alive; the atria walls are thin and
probably collapsed when the dinosaur died. 

Modern reptiles have three-chambered hearts, with two
aortas and only one ventricle; crocodiles have two
ventricles but they are incompletely separated. Thus,
oxygenated blood from the lungs and deoxygenated blood
from the rest of the body become mixed together in
these reptilian hearts, reducing the overall oxygen
content of blood returned to the body and limiting the
metabolic rates and activity of these animals. 

"A single systemic aorta communicating with the left
ventricle greatly reduces the risk of shunting and can
be considered a means of more efficiently supporting
prolonged periods of high activity," the discovery
team said in its report. 

What makes the discovery especially surprising and
puzzling is that the heart resembles a mammal's or
bird's but it belonged to an ornithischian, or
bird-hipped, dinosaur, one of the two main lineages of
these great reptiles. Despite the name, these
dinosaurs were far removed from those who were
presumed by many paleontologists to have been
ancestors of birds; these ancestors were presumed to
be theropods, members of the other main lineage known
as the saurischian, or lizard-hipped, dinosaurs. 

It is therefore possible, Dr. Russell said, that
dinosaurs of both lineages -- not just the bird
ancestors -- had advanced hearts and high metabolisms.
This physiology may have evolved independently or it
could stretch all the way back to a common ancestor,
some 235 million years ago. 

"This means our entire conception of dinosaurs may
have to be revised," said Dr. Norell of the American
Museum. 

All the discovery team would say in its report was,
"Whether high metabolic rates and advance hearts arose
once or more than once among dinosaurs remains an open
question." 

                        *  *  *





=====
Larry

"I've been ionized, but I'm OK now."

http://members.tripod.com/~megalania/index.html

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