A Dinosaur Walks into the Museum

What scientific "detectives" deduced from the biggest footprints ever found

limestone ledge

 A JUTTING LIMESTONE LEDGE is in the way, so it must go: broken sections being moved away with the aid of bars and rollers. It contained many fossil oyster shells and other marine invertebrates left there when the sea advanced over the area. Why have no sauropod tracks been discovered farther north in the United States, where skeletons of the animals have been found in large numbers? Dr. Brown deduces that only in seaside mud flats, as distinct from lake marshes, would the putty-like earth of decomposed marine organisms be firm enough to receive and hold the impression of the feet while underwater. Preliminary examination of the rock bears out the conclusion that the dinosaurs here were wading in a shallow, brackish arm of the sea, though the spot is now almost 300 miles from the coast. Farther north, where sauropods frequented the lakes, they died in great numbers in diminishing pools when the drying up robbed them of the water necessary to their existence.

Roland T. Bird

two dinosaur paths

Left: WITH the limestone ledge blasted and cleared away, Trail Two stands out clearly on the right. Other trail disclosures indicate that no less than a dozen sauropods had crossed this section. All were progressing in the same direction as a herd moving across a shallow mud fiat. Right: MOST INTERESTING FEATURE uncovered during the season’s work was the trail of a flesh-eating dinosaur following that of a sauropod. This is seen at the left of Trail Two as a row of three-toed footprints. Made at a time when the mud was of the same consistency, these prints suggest that a fourteen-foot flesh-eater was actually stalking the big quadruped. At any rate, when the sauropod swung to the left, the carnivorous dinosaur did likewise. Along this ancient waterfront, the territory of these two distinctively different types of dinosaurs overlapped.

Roland T. Bird

removing slab of dinosaur tracks

Left: PREPARATIONS are made to remove the first slab of tracks, 29 feet long by eight feet wide, to be placed under the tail in the base of the Brontosaurus skeleton in the American Museum. Most fortunate circumstance of the entire season was the comparative thinness of the track-bearing layer, which was less than eighteen inches thick. The rock rested on a four-foot bed of soft clay and was not difficult to cut with chisels. The sequence and association of fore and hind foot impressions are typical of the trail made by any slow-moving, very heavy four-footed animal. Later a suitable section of the flesh-eating dinosaur trail was taken. Right: HOW REMOVAL of this 30,000-pound track slab was possible. In addition to the fortunate bed of clay underneath, the block also had convenient cross-fractures which allowed easy blocking off into sections. The edges were then covered with plaster jackets to preserve clean contacts, sections were given numbers, and their relationship recorded on a chart, so that re-assembly would present no problem.

Roland T. Bird

Recent Stories

The way they live, the food they eat, and the effect on us

A true but unlikely tale

Story and Photographs by William Rowan

Increasing day length on the early Earth boosted oxygen released by photosynthetic cyanobacteria.

Genomic evidence shows that Denisovans and modern humans may have overlapped in Wallacea.