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
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.