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.