Ancient reptile was designed for stealth

Medicine & Science

September 27, 2004|By William Mullen | William Mullen,CHICAGO TRIBUNE

Looking and acting something like an underwater canister vacuum cleaner, a prehistoric marine reptile apparently used its extremely long neck to sneak up on and suck in unwary fish swimming in murky shoreline waters 230 million years ago.

The creature was discovered two years ago in China and named Dinocephalosaurus orientalis, or "terrible-headed lizard from the Orient." Figuring out what the fossil was and how it lived took the combined skills of the Chinese paleontologist who found it, an expert on fossil reptiles from the Field Museum in Chicago and a University of Chicago expert in biomechanics who studies how scallops swim.

The three share authorship of an article in last week's edition of the journal Science that introduced Dinocephalosaurus.

Dinocephalosaurus was a protorosaur, a group of lizard-like predatory reptiles. Some protorosaurs lived on land; others, like this one, evolved from an early protorosaur that crawled back into the sea and became a fully aquatic animal.

Dinocephalosaurus was probably a pretty diabolical hunter, said Michael LaBarbera, the University of Chicago professor of organismal biology and anatomy who studied the fossil.

Its 5-foot neck was nearly twice as long as its body, he said, but it had a small head, only about five inches long.

"It lived in mucky waters near the shore, where it would be an advantage to have your head and brain out on the end of a long spar," he said. "A fish swimming there would see something dark coming out of the gloom in the water but wouldn't be alarmed because it would see that it was about its own size."

Dinocephalosaurus' long neck was made up of 25 elongated vertebrae, each of which had even longer, delicate cervical rib bones attached. As the reptile stretched and straightened its neck to reach the fish or squid it wanted to eat, the ribs flared out, at least doubling the size of its esophagus.

When the creature opened its toothy mouth, water would rush in, suctioning in the targeted fish or squid before it could dart away. The creature's open mouth also swallowed the small pressure wave created by its moving head, eliminating the last possible warning to its prey.

"The teeth on this thing are quite distinctive, fairly slender and kind of needlelike, pointing back into the mouth, ideal for capturing slippery prey like fish and squid," said LaBarbera. "Once they were down in the esophagus, it would partially open its mouth to expel the water, but the teeth kept the prey caged in."

Though protorosaur fossils, both land and marine versions, had been found in other parts of the world, Dinocephalosaurus is the first found in China.

Chinese paleontologist Chun Li, a professor at Beijing's Institute of Paleontology and Paleoanthropology, discovered it in 2002 in Triassic limestone formations among the mountains of Guizhou province in southwest China. The next year he found an almost complete fossil of a Dinocephalosaurus body and a second skull.

In the past couple of decades, China has taken a keen interest in its rich deposits of fossil rocks. Several years ago, the Beijing Institute began inviting the Field Museum's Olivier Rieppel to collaborate on analyzing and publishing findings.

When Rieppel brought home data on Dinocephalosaurus, he kept wondering about the purpose of its long neck vertebrae, with their attached ribs:

"I just got nowhere with it, so I took it to Michael LaBarbera and asked him to take a look."

LaBarbera studies biomechanics, or how animals physiologically operate. "Many marine animals do suction feeding like this, including turtles and salamanders," he said. "Reptiles have very ... expandable throats, grabbing, killing and swallowing their prey whole."

The Chicago Tribune is a Tribune Publishing newspaper.

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