|Click image to enlarge|
Fossilized bones which formed part of the left wing. Photo courtesy Southern Methodist University, Dallas.
Fossilized bones from a gigantic flying reptile recently discovered in Texas may be the earliest record yet of the prehistoric creature known as Pteranodon. Previously, similar remains have been unearthed in Kansas, South Dakota and Wyoming, but this likely Pteranodon specimen is the first of its kind found in Texas, according to paleontologist Timothy S. Myers, who is based at Dallas's Southern Methodist University. The specimen was discovered north of the city by an amateur fossil hunter who found various bones belonging to the left wing.
Pteranodon was a type of pterosaur first being seen in the fossil record about 100 million years ago. As the only reptiles to dominate the ancient skies, pterosaurs had broad leathery wings and slim torsos. The specimen identified by Myers is an adult pterosaur, which had a wingspan of 12-13 feet. It was discovered in the Austin Group, a prominent rock unit in Texas that was deposited around 89 million years ago, early in the geological time period known as the Late Cretaceous.
A different landscape
Pterosaurs, many of which survived on fish, lived at a time when a massive ancient sea cut across the central United States. The western interior seaway was a shallow body of water that split North America in half, from the Arctic Ocean to the Gulf of Mexico.
More than a thousand Pteranodon fossils have been unearthed from what was the middle part of the seaway, but this new find would represent the most southerly discovery to date.
The bones of pterosaurs, like birds today, were often hollow. This reduced their body weight, making it easier for them to fly. Unfortunately however, the delicate humerus, which is the bone attaching the wing to the body, was damaged during the fossilization process in this case, making precise identification difficult. Other features, however, clearly identify the specimen as a member of the pteranodontid family.
|Click image to enlarge|
Pterosaurs hunted for fish over the western interior seaway, which used to split North America.
There are no clues as to why this pteranodon died, but it was probably flying over the sea and then fell into the water. Its carcass is likely to have floated for some time, so that as the flesh decomposed, the bones came apart at the joints - a process known as 'disarticulation' - before they settled on the sea floor and were buried.
"We know it was disarticulated when it was buried because the bones weren't preserved in the correct anatomical position," Myers explained. "Abrupt truncation of the broken end of one of the bones and infilling of the break with sediment also indicates that the breakage and disarticulation took place prior to burial."
Oldest North American find?
According to Myers, if the fossil is of Pteranodon, this would be the oldest record from North America by 1-2 million years, and it would also be the second oldest recorded pteranodontid in the world.
"Any pterosaur material is fairly rare to find unless you have exceptional preservation conditions, because of the fragile bones of these reptiles. They needed to be buried rapidly in order to be well-preserved," said Myers. "This particular specimen sank some distance from the shoreline in water which was perhaps 50-80 feet in depth. It's a fairly exceptional find, as typically you'll only find one piece of the skeleton, or part of a piece in the local rock."
Reference: Timothy S. Myers. Earliest Occurrence of the Pteranodontidae (Archosauria: Pterosauria) in North America: New Material from the Austin Group of Texas. Journal of Paleontology, 2010; 84 (6): 1071 DOI: 10.1666/09-082.1