Earth

Pteranodon: A curious case in Texas

An amateur fossil hunter made a curious find: pieces of wing bones embedded in rock, just north of Dallas. The fossils were identified by Timothy Myers, a paleontologist at Southern Methodist University, as belonging to a pterosaur, a flying reptile that graced the skies during the age of the dinosaurs. Furthermore, Myers believes that the bones belonged to a Pteranodon, a type of pterosaur known from fossils found in Kansas, Alabama, Nebraska, Wyoming, and South Dakota. This 89-million-year-old specimen may be the oldest known pteranodon, and the only known specimen to date found in Texas.

Pterosaurs were flying reptiles with broad leathery wings that lived world-wide from the Triassic to the Cretaceous periods – that’s 220 to 65 million years ago. They were the only ancient reptiles that dominated the skies during the age of the dinosaurs. Pterosaur fossils, generally found as disarticulated pieces of bone, are quite rare because of the animals’ fragile bones. In order to be preserved as fossils, the bones required rapid burial. From the fossil record, paleontologists have learned that pterosaurs from the early Cretaceous had thin sharp teeth. But over time, the toothed pterosaur species disappeared, and by the late Cretaceous, only toothless pterosaurs remained. Both toothed and non-toothed types have been found in North America, including a toothed species called Aetodactylus halli, from 95 million years ago, found in the Dallas area.

Pteranodon were a type of pterosaur – the kind without teeth – that lived between 100 million and 65 million years ago. Back then, North America was split from north to south by a narrow sea called the Western Interior Seaway. Pteranodon were thought to have hunted for fish in that sea. Over a thousand fossils have been found in the middle of the seaway, in present-day Kansas, South Dakota, and Wyoming.

The 89-million-year-old wing bones found near Dallas, strongly suspected to be those of an adult Pteranodon, are significant for several reasons. The find could indicate the animals’ southernmost range along the Western Interior Seaway. It could be the earliest known pteranodon in North America, and it could be the first of its kind ever found in Texas. The bones were found by Gary Byrd of Rockwall, Texas, about 10 years ago, in what’s known as the “Austin Group,” a rock outcrop north of Dallas that was deposited about 89 million years ago.

According to Myers, this animal would have had a wingspan between 12 and 13 feet long (3.6 to 4 meters). The key feature that led Myers to conclude it was likely a Pteranodon was the humerus, about 5.7 inches (14.5 cm) long, the part of the bone that connects to the torso. Even though the humerus had been compressed under the weight of the rock, it held features that indicated the likelihood of it being a pteranodon. Also part of the fossil find were sections of wing: an incomplete section of metacarpal and part of a long “fourth finger.” Myers speculated that this Pteranodon met its end while flying over the sea. Its body fell into the water, and after floating for a while, began to decompose, causing bones to separate at the joints and fall to the ocean floor where they were eventually buried.

Even though the evidence is not definitive, there’s a high probability that the fossil wing bones found north of Dallas, dated to 89 million years ago, could be the first known Pteranodon found in Texas. If so, paleontologist Timothy Myers of Southern Methodist University believes that this flying reptile, which once soared above the dinosaurs of the late Cretaceous period, could be the oldest known specimen of its kind in North America, and might set a new southernmost range for Pteranodon along the ancient Western Interior Seaway.

Posted 
March 13, 2011
 in 
Earth

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