Frequently Asked Questions:

Q. What kind of dinosaurs made tracks?
A. Nobody knows exactly what species made the tracks, but vertebrate paleontologists can make a good guess.

Two main types of track makers were common in the Cretaceous of Texas-animals that walked on four feet (quadrupedal) and those that walked on their two hind feet (bipedal).

Bipedal tracks in the Cretaceous rocks of Texas probably were made by several groups of dinosaurs, including theropods and ornithopods. These dinosaurs, like birds of today, walked on their toes, leaving three-toed prints. Comparing the teeth of these dinosaurs with animals living today reveals that the dinosaurs were probably carnivorous. Vertebrate paleontologists have proposed that the Glen Rose theropod track maker that had sharp toenails could have been Acrocanthosaurus. Other possible track makers are shown at the Fort Worth Museum of Science and History. Blunter three-toed tracks could have been made by the ornithopod from a group known as Iguanodons . Smaller three-toed tracks might have been made by young members of these species or by any one of a number of smaller bipedal dinosaurs.

Quadrupedal tracks are interpreted as the tracks of sauropods—large, long-necked dinosaurs. Dinosaur researchers propose likely makers of the tracks at Dinosaur Valley State Park are Pleurocoelus or Sauroposeidon. The skeleton of a proposed sauropod track maker is on exhibit at the Fort Worth Museum of Science and Technology. Large (3-foot-wide) depressions were made by hind feet. Prints of front feet are somewhat U shaped, but they have sometimes been damaged or eliminated by the hind footprints coming after and obliterating them. The animals' peglike teeth suggest that they browsed on shrubs and other vegetation.

Q. How much did dinosaurs weigh?
A. Comparing the size of the footprint and length of the animal's stride with those of modern animals having similar locomotion helps scientists estimate the size of the track-making animal.

The largest sauropod track makers had hind footprints about 3 feet across and 18 inches deep and strides of as much as 10 feet. These giants weighed 30 tons and may have been more than 40 feet long. The three-toed track-making animals were smaller, making tracks 20 inches across and 5 inches deep. Their weight is estimated to be as much as 2 to 3 tons and their length as much as 25 feet. However, the stride in these trackways is as much as 9 feet, nearly as long as that of the sauropods, showing that the bipedal dinosaurs had a more efficient gait and they may have been capable of greater speed!

You can estimate how fast a dinosaur moved from its foot size and stride length. See instructions here (PDF).

Q. What do scientists learn from trackways?
A. Tracks provide direct information about how animals behaved that is difficult to get from fossil skeletons.

Trackways have helped researchers:

Understand that both plant-eating and meat-eating dinosaurs carried their large, long tails in the air. Click here or on on the picture for more information.
Confirm that although they were very large compared with most animals today, dinosaurs were strong enough to walk on land. Click here or on on the picture for more information.
Show that dinosaurs stood upright like elephants of today. Click here or on on the picture for more information.
Show that some dinosaurs traveled in herds. The occurrence of four or five tracks all curving together across what appears to have been a broad mudflat suggests that the animals were traveling together. In fact, some carnivorous-dinosaur tracks curve the same way as those of the herbivores, suggesting that they may have belonged to predators trailing the herd. Traveling in herds with young animals in the middle is common behavior in large herbivores today.
Suggest that carnivorous dinosaurs could move rapidly, with 9-foot strides.
Show the arrangement of skin, muscle, and other soft tissue on their feet and hip height of the animal. Click here or on the picture to see tracks, bones and reconstructions of dinosaur feet.

Q. What kept dinosaurs from walking all over the state?
A. You may have noticed that the tracks are mostly in one part of Texas, stretching from Pecos County through San Antonio, north to Dallas and into Arkansas. Why are tracks not found in Houston, Midland, and Lubbock?

One reason is that this belt of rock is an outcrop of rocks of Lower Cretaceous age, which was deposited during the Mesozoic, the "age of dinosaurs." The rocks of the Llano region and parts of west Texas are too old-dinosaurs (in fact most land-dwelling species) had not yet evolved when these rocks were deposited. The rocks of the top of the High Plains and across the Gulf of Mexico coastal plain are too young, deposited after dinosaurs were extinct.

Texas cross-section showing where and why tracks were found.

West of the area where tracks are found, Lower Cretaceous rocks have been eroded. East of the area, Lower Cretaceous rocks have been buried. So although dinosaurs most likely walked all over Texas, the only place that we can see evidence is in the middle of the state.

Habitat during the Early Cretaceous was suitable for dinosaurs. During the Early Cretaceous, Texas was on the coast of a shallow ocean at 25° north latitude (a little further south than Texas is now). Dinosaurs left their tracks on muddy flats and in shallow water on an extensive plain. Preserved coaly layers record vegetation that grew in swamps along this coast. Younger Middle and Upper Cretaceous rocks were deposited mostly in marine environments, so the fossils they contain are of marine reptiles—the Onion Creek mosasaur, for example.

Farlow, J. O., 1993, The dinosaurs of Dinosaur Valley State Park, Somervell County, Texas: Austin, Texas, Texas Parks and Wildlife Department, unpaginated.
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