Aetodactylus halli, a new pterosaur has just been described on the basis of a 95-million-year-old jaw discovered in Texas.

The specimen is one of the youngest to be assigned to the family Ornithocheiridae, according to paleontologist Timothy S. Myers, who identified and named Aetodactylus halli. It's only the second ornithocheirid documented in North America, says Myers, a post-doctoral fellow at Southern Methodist University (SMU), in Dallas.

Pterosaurs were the first vertebrates to fly — earlier than even the earliest bird (So who gets the worm?). Popularly, they are still often called pterodactyls, the older name for these winged creatures of the Mesozoic.

Found in the Dallas-Fort Worth area, the jaw once belonged to an animal that met its demise in a plunge to the bottom of the Western Interior Seaway (see map right), which then blanketed the Lone Star State. The massive sea split North America, from the Gulf of Mexico to the Arctic Ocean.

While rare in North America, the toothed pterosaurs of Ornithocheiridae are an important component of Cretaceous pterosaur faunas elsewhere in the world. This specimen — a nearly complete mandible with most of its 54 teeth missing — is younger than most other ornithocheirid specimens from Brazil, England and China, he says, and five million years younger than the only other known North American ornithocheirid.

Myers describes Aetodactylus halli in the latest issue of the Journal of Vertebrate Paleontology.

Myers named the creature after Lance Hall, a member of the Dallas Paleontological Society who hunts fossils for a hobby. Hall, who donated the specimen to SMU, found it in 2006, embedded in a soft, powdery shale exposed by road excavation. The site is near the city of Mansfield, southwest of Dallas.

Just a bit of the jaw lay exposed

The Aetodactylus halli jaw was discovered in the geologic unit known as the Eagle Ford Group, which comprises sediments deposited in a shallow sea, Myers says. Outcrop of the Eagle Ford Group extends northward from southwestern Texas into southern Oklahoma and southwestern Arkansas.

"I was scanning the exposure and noticed what at first I thought was a piece of oyster shell spanning across a small erosion valley," Hall recalls of the discovery. "Only about an inch or two was exposed. I almost passed it up thinking it was oyster, but realized it was more tan-colored like bone. I started uncovering it and realized it was the jaw to something — but I had no idea what. It was upside down and when I turned over the snout portion it was nothing but a long row of teeth sockets, which was very exciting."

Unique jaw differs from others

The 38.4-centimeter Aetodactylus jaw originally contained 54 slender, pointed teeth, but only two remain in their sockets, Myers says. The lower teeth were evenly spaced and extended far back along the jaw, covering nearly three quarters of the length of the mandible. The upper and lower teeth interlaced when the jaws were closed.

In Aetodactylus, changes in tooth size along the jaw follow a similar pattern to those of other ornithocheirids. However, Aetodactylus differs from all other ornithocheirids with regard to its delicate jaw, with a maximum thickness of little more than 1 centimeter, Myers says. But the specimen does compare favorably with Boreopterus, a related pterosaur from the Early Cretaceous of China, in terms of the number of teeth present in the lower jaw, he says.

Myers estimates the wingspan at roughly three meters, or about ten feet, so Aetodactylus would have been a medium-sized pterosaur.

Texas now claims the only two of their kind

The first specimen of an ornithocheirid from North America, a snout found in Fort Worth in 1992 by amateur collector Chris Wadleigh, was formally described as Coloborhynchus wadleighi.

Except for Aetodactylus and Coloborhynchus, Myers says, All North American pterosaurs dating from the Cretaceous were toothless. The thinness of the jaw, the upward angle of the back half of the mandible and the lack of a pronounced expansion of the jaw's tip all indicate that Aetodactylus was different from other ornithocheirids. Myer asserts that discovery of this unusual ornithocheirid, "in Texas hints at a diversity of pterosaurs in the Cretaceous of North America that wasn't previously realized."