Newly discovered dinosaur tracks in Colorado's fossil-rich Cretaceous rock preserve evidence of frenzied activity. As with most fossilized foot markings, these prints and scratches were not made by dinosaurs carefully placing their feet in cement like Hollywood stars, but by active animals. And the abundance, arrangement, and shapes of these tracks suggest these theropod trackmakers were particularly stirred up. But what were they stirred up about? Paleontologist Martin Lockley, who discovered and analyzed the tracks, has some very definite ideas about that.
The Dinosaur Whisperer
Lockley, in the journal Scientific Reports, describes large random groupings of six-foot-long scrapings gouged 8–12 inches deep into Colorado's Dakota Sandstone. Most consist of parallel scratches with a raised ridge between furrows. Some show the three-toed footprints of their clawed bipedal printmakers, possibly the 16-foot-long theropod Acrocanthosaurus. Though fossils do not dance, Lockley sees in these dugouts from the past the ritualized mating dance of ancient T. rex-like theropods. Why? Because some ground-dwelling birds today dance to attract their mates, and Lockley (like most evolutionists today) believes birds evolved from dinosaurs.
Lockley found groups of fossilized gouges at four Colorado sites. The largest featured about 60 grooved scrapes on an exposed surface area of about 750 square meters (over 8,000 square feet). He has preserved the visible fossil record of these dinosaurs' activities using 3D photographic images1 and casts. The tracks have been unroofed by erosion after their long-ago burial and fossilization, supposedly around 100 million years ago. Fossilized ripple marks attest to the movement of water associated with the activity of the theropod trackmakers or of the process that preserved their tracks.
Looking at the footprints, Lockley says they "went crazy scraping. These animals would have been really frenzied." He believes that the best explanation for these fossilized tracks is a mating dance and that the groupings represent arenas in which these ritualized dances were performed. "These are the first sites with evidence of dinosaur mating display rituals ever discovered, and the first physical evidence of courtship behavior," says Lockley. "These huge scrape displays fill in a missing gap in our understanding of dinosaur behavior."