Accordingly, a normally bipedal dinosaur that could have gone onto all four limbs was a facultative quadruped . Nevertheless, tracks and trackways, because they are nearly always in-situ records of dinosaur behavior, represent valuable information about what dinosaurs lived in an area during certain times, how they evolved, how individuals behaved, and how they interacted. The first dinosaurs are thought to have been bipedal descendants of archosaurs that evolved during the Triassic Period. Dinosaur tracks from the Late Triassic, which show bipedalism, support this hypothesis. All theropods were obligate bipeds, although some rare examples of trackways show that they went down onto all fours, meaning some of them were facultative quadrupeds.
Some tracks show claw impressions at the ends of toes.
Theropods trackways show little deviation from the midline of travel, as if they were walking on a tightrope. This foot belongs to Allosaurus , a large Jurassic theropod. Notice the three toes with a relatively narrow width. This foot belongs to Tyrannosaurus , a large Cretaceous theropod. Although separated by millions of years, both Allosaurus and Tyrannosaurus would have left similar footprints that were attributable to large theropods.