Glen Rose Formation - Dinosaur Footprints and Trackways

Dinosaur Footprints and Trackways

Dinosaur footprints and trackways are found in at least 50 localities in the Glen Rose, primarily at the top of the Upper Glen Rose and a smaller number at the top of the Lower Glen Rose. The most famous of these sites is the Paluxy River site in Dinosaur Valley State Park near the town of Glen Rose, Texas, southwest of Fort Worth. In 1938, Roland T. Bird, assistant to Barnum Brown of the American Museum of Natural History ("AMNH") in New York, New York, discovered a dozen sauropods and four theropod or carnosaur trackways all following the same general direction. These were the first sauropod footprints scientifically documented, and were designated a National Natural Landmark in 1969. Some are as large as about 3 feet (1 m) across. The prints are thought to have been preserved originally in a tidal flat or a lagoon. Large slabs of the trackways were excavated and are on display at the AMNH and the Texas Memorial Museum in Austin, Texas, among other institutions.

The sauropod tracks, now given the ichnogenus name Brontopodus, were made by an animal of 30 to 50 feet in length, perhaps a brachiosaurid such as Pleurocoelus, and the theropod tracks by an animal of 20 to 30 feet in length, perhaps an Acrocanthosaurus. A variety of scenarios was proposed to explain the tracks. Some believed that they recorded a herd of sauropods, including young animals protected by their parents, being followed by a group of theropods and argued that the apparent disappearance of one of the sauropod trackways indicated a fatal attack by the theropods. Scientists today generally discount this explanation. Martin Lockley (1995) concludes that the tracks most likely represent twelve sauropods "probably as a herd, followed somewhat later by three theropods that may or may not have been stalking -- but that certainly were not attacking." Lockley notes that there are other similar group trackways and that the evidence sauropods moved in herds "in general, seems good." He takes issue, however, with Robert Bakker's theory that the Davenport Ranch trackway (another Glen Rose trackway) reflects large adults on the outside, protecting younger sauropods in the center, stating that the trackways merely show smaller animals following the larger ones. The fact that some of the Glen Rose trackways primarily include marks of the fore feet led Bird and others to suggest that the sauropods were semi-aquatic and made the tracks when partially swimming, a scenario that "has become deeply entrenched in the popular literature..." Again, Lockley discounts that theory, stating that the tracks were not well preserved or studied and that the view of sauropods as swimming "can not be supported using any convincing line of available evidence."

The debunked Creationist claim that human footprints have been found in the Glen Rose is discussed in the Dinosaur Valley State Park article.

• See further The Heritage Museum of the Texas Hill Country website