SPECTACULAR FOSSIL REVEALS DINOSAUR SOFT PART ANATOMY AND SUPPORTS COLD-BLOODED DINOS NOT RELATED TO BIRDS
From the New York Times, January 26, 1999 as reported by Malcolm W. Browne
By shining ultraviolet light on the fossil of a baby dinosaur that had collected dust in a file drawer in Italy for 15 years, paleontologists have discovered astonishingly well-preserved anatomical details that have rekindled one of the most intense debates in paleobiology.
The discovery has cast doubt on two widely held theories: that dinosaurs were warm-blooded and that they were the ancestors of birds.
Many paleontologists in recent years have come to accept the theory that at least some dinosaurs could maintain steady body temperatures by themselves. Many paleontologists are also convinced that birds are closely related to dinosaurs, probably as their direct descendants. part of the evidence for this is the striking similarity of the skeletons of some dinosaurs to those of birds.
The baby dinosaur recently examined was the first found embedded in a limestone formation north of Naples in 1983. Last year, after its rediscovery in in the Archaeological Administration in Salerno, paleontologists who examined it were astonished to find that much of its flesh, including many of its internal organs, had been preserved in fossil form - an extraordinary discovery. The unique fossilized dinosaur, named Scipionyx samniticus, has by far the best preserved fossil organs of any dinosaur ever found, scientists agree.
(PHOTOS FROM SCIENCE)
Since the initial investigation, which was reported a year ago, a team of paleontologists headed by Dr. John A. Ruben of Oregon State University at Corvallis and Dr. William J. Hillenius of the College of Charleston, S.C., has examined the fossil under ultraviolet radiation. On Friday the journal Science published the result: a spectacular picture in fluorescing colors, in which the little animal's organs stand out as vividly as color-coded engineering diagrams.
"It's amazing," said Dr. Larry Martin, a paleontologist at the University of Kansas. "It's essentially a dinosaur that's been dissected."
Paleontologist who have seen the ultraviolet pictures of Scipionyx agree that they are uniquely revealing. But experts are far from agreeing on the interpretation of the images.
Dr. Ruben and his colleagues argue that the fossil provides strong evidence that dinosaurs had a breathing mechanism similar to that of modern crocodiles and completely different from that of birds. From this and some other evidence, they deduced that theropod ("beast footed") dinosaurs, including the mighty Tyrannosaurus rex, were cold-blooded, but were capable of spurts of intense activity.
A member of Dr. Ruben's group, Nicholas R. Geist, said, "What you have is a turbocharged reptile."
Scipionyx, which in life probably somewhat resembled the fierce velociraptors depicted in the movie "Jurassic Park", lived about 110 million years ago. This specimen, an infant that apparently died shortly after it was hatched, failed to attract much scientific interest at the time it was found.
But it was later discovered that its different body parts were selectively mineralized by different chemicals in the marine sediments in which it was buried. This causes the fossilized organs to fluoresce in different colors when exposed to ultraviolet.
The animal's colon glows bright yellow and appears to lie very close to its spinal column. In modern reptiles, the colon is arranged like this only in crocodiles, Dr. Ruben said.
In another possible similarity with crocodiles, scientists found evidence in the infant dinosaur of a specialized breathing device called a hepatic piston. In the crocodile, Dr. Ruben said, the piston is a large liver driven by muscles that pull it in and out to move air through the lungs. The colon lies near the crocodile's spine to leave room for the liver to move freely.
Scipionyx's lungs themselves were not preserved, but Dr. Ruben identified a large organ that glows blue under ultraviolet light as its liver. The relative positions and sizes of these and other organs mark them as crocodilian in type, he said.
By contrast, Dr. Ruben said, a bird's colon extends right through the middle of its abdominal cavity.
"It seems clear," he said in an interview, "that a bird's radically different system of breathing, in which air is continuously drawn through the lungs, could not have evolved from the hepatic-piston system we see in this theropod dinosaur."
The indications, however faint, that Scipionyx had diaphragmatic muscles to assist its liver piston in breathing suggest that the animal many have been an ectotherm (cold-blooded), but was capable of sustaining oxygen consumption rates and activity levels beyond those of modern reptiles, Dr. Ruben said.
These views were strongly endorsed by Dr. Alan Feduccia, an ornithologist at the University of North Carolina, who has long argued that birds could not have descended from dinosaurs.
"I think John Ruben has done a remarkable job - a nice piece of detective work on a beautiful specimen," Dr. Feduccia said.
But Dr. Lawrence Witmer, an evolutionary biologist at Ohio University's College of Osteopathic Medicine in Athens, was one of the experts who challenged Dr. Ruben's conclusions.
"We have a ton of evidence for the view that birds descended from theropod dinosaurs, and John Ruben's conclusions fly in the face of this abundant evidence," Dr. Witmer said.
"He raises some intriguing points," he added, "but I'm not convinced that we're really seeing a hepatic piston in a fossil. Remember, we're seeing it in crushed form. Also, how do we know that bird breathing systems could not have evolved from crocodile-like systems? The history of life has often confounded theory."
He said that Dr. Ruben's ideas might turn out to be correct, but that further evidence was needed to settle some large doubts.
Dr. Martin, of the University of Kansas, suggested, however, that the evidence already appeared to be in hand.
Regarding the conclusions of the Oregon State University team, he said: "There's actually no way they could be wrong about this. The Scipionyx specimen has the best preservation ever seen. It's one of the biggest discoveries of this decade. It tells us more about dinosaurs than any other specimen.
"The positions of the dinosaur's windpipe and colon serve as independent checks that the animal did not have a bird's breathing apparatus," he said. And, he said, the external shape of theropod dinosaurs, "with deep, narrow body walls, is exactly the design you would expect for an animal with a hepatic piston."
As for the scientists who hold to the bird-dinosaur connection, he said: "They're really cast in stone. Despite this new evidence, it's going to be very hard for them to change their minds now."
For More Information See SCIENCE, 22 January 1999, vol 283, no. 5401:
Ruben, J.A., et al., Pulmonary Function and Metabolic Physiology of Theropod Dinosaurs, p.514-516. (Original Article)
News of the Week, Paleontology: Stunning Fossil Shows Breath of a Dinosaur, p.468.