A long-necked sea predator from China described in Science
Scientists have discovered a long-necked sea reptile with fangs that probably preyed on fish and squid in a shallow sea in present-day southeast China more than 230 million years ago. The creature's relatively stiff, 1.7-meter-long neck (approximately five and a half feet) was almost twice as long as its trunk which measured less than one meter in length. These findings appear as a "Brevia" article in the 24 September, 2004 issue of the journal Science published by AAAS the nonprofit science society.
The creature is the first report of a fully marine member of a diverse reptile group called the protorosaurs which are characterized by their long necks and elongated neck vertebrae. Comparison of this new creature to the famous long-necked reptiles and a fellow protorosaur from Europe and the Middle East called Tanystropheus offers new insights into protorosaur hunting strategies as well as their evolution and diversity during the Triassic Period.
The new creature's specialized neck ribs may have helped the aquatic reptile hunt. The sea predator's hunting strategies, as proposed by the authors, may cause others to revisit conclusions about how Tanystropheus and other protorosaurs used their necks during the hunt, said coauthor Olivier Rieppel from the Field Museum in Chicago, Illinois.
Author Chun Li from the Chinese Academy of Sciences in Beijing, China discovered the reptile in two phases. Li named the creature Dinocephalosaurus orientalis, meaning "terrible headed lizard from the Orient," after he discovered the 23.5-centimeter-long skull (about 9 inches) in autumn of 2002 in the Guanling Formation in China's Guizhou Province. Three fang teeth in the upper jaw from this skull survived: front to back, they measured 1.5 centimeters, 2.8 centimeters and 2.3 centimeters in length.
Later that year, in the same marine limestone, Li discovered a nearly complete skeleton of China's first protorosaur. This skull measured 15.5 centimeters in length (about 6 inches).
While Tanystropheus had a giraffe-style neck comprised of a small number (12) of extremely elongated neck or cervical vertebrae, the new fossil's long neck contains 25 somewhat less elongated neck vertebrae.
With relatively short and broad limbs containing few bones, Dinocephalosaurus, more than other protorosaurs, appears fully designed for life in the water. Though protorosaurs with more extensive bony limb structures would have had an easier time on land, Chun Li said Dinocephalosaurus may have ventured onto land to lay eggs.
To breathe, Dinocephalosaurus probably held its neck parallel to the water's surface. Extending the head and neck vertically to gulp air would have been impossible because surrounding water pressure would have prevented the lungs from inflating.
Both Dinocephalosaurus and Tanystropheus have rib-like bones that extended parallel to the neck vertebrae, bridged the space between vertebrae and restricted neck movement. (These ribs prevented the extreme neck flexibility seen in herons, for example.) The authors report that Dinocephalosaurus' long neck presumably served a functional role in hunting and present two possible strategies.
With its long slender neck and small head, the reptile may have been able to sneak up and lunge at a fish or other aquatic prey in murky near-shore waters before the predator's full profile scared off the potential meal.
Based on Dinocephalosaurus' tooth and fang arrangement which is unlike other protorosaurs, the creature could have attacked with jaws opening sideways like a crocodile.
Coauthor Michael LaBarbera from the University of Chicago in Chicago, Illinois proposed a second hunting strategy that would have required participation from the pliable ribs that ran along the sides of the neck. Contraction of Dinocephalosaurus' proposed neck muscles could have rapidly straightened the neck and splayed the neck ribs outward. This could have increased throat volume enough to allow the animal to swallow the pressure wave that it created as its head lunged forward though the water. By swallowing its own pressure wake that would otherwise signal its approach, the predator may have executed almost undetectable strikes at unsuspecting fish.
While it's difficult to add muscles to a fossil when there is little or no evidence for muscles in the fossil record, and even tougher when the fossil has no living counterpart, Rieppel said their ideas are based on the preserved bone structures, biomechanics and the complexities of hunting in water, a dense medium that can alert prey to a predator's presence long before it strikes.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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