Many animals have left records of their movements over dry land or the sea bottom. Some of these, such as footprints ([Pl. 4]), indicate not only the type of animal that left them but often provide valuable information about the animal’s environment.
Thus, the study of a [series] of dinosaur tracks would not only indicate the size and shape of the foot but also provide some information as to the weight and length of the animal. In addition, the type of [rock] containing the track would help determine the conditions under which the dinosaur lived.
Some of the world’s most famous dinosaur tracks are to be found in the Lower [Cretaceous] limestones in Somervell County, Texas. These footprints, which are about 110,000,000 years old ([Pl. 4]), were discovered in the bed of Paluxy Creek near the town of Glen Rose. Large segments of the [rock] containing these tracks were collected by paleontologists of the American Museum of Natural History in New York City and the Texas Memorial Museum at Austin. Great slabs of limestone were transported to the museums, replaced in their original position, and are now on display as mute evidence of the gigantic size of these tremendous reptiles.
Invertebrates also leave tracks and trails of their activities, and these markings may be seen on the surfaces of many sandstone and limestone deposits. These may be simple tracks, left as the animal moved over the surface, or the burrows of crabs or other burrowing animals. Markings of this sort provide some evidence of the manner of locomotion of these organisms and of the type of environment that they inhabited.
Coprolites
Coprolites are [fossil] dung or body waste ([fig. 1]). These objects can provide valuable information as to the food habits or anatomical structure of the animal that made them.
Fig. 1. Sketch of a [coprolite]—fossilized animal excrement.
Gastroliths
These highly polished well-rounded stones ([fig. 2]) are believed to have been used in the stomachs of reptiles for grinding the food into smaller pieces. Large numbers of these “stomach stones” have been found with the remains of certain types of dinosaurs.