Excavating the River of Giants

In the American Museum of Natural History’s Hall of Saurischian Dinosaurs, there is a great fossil mismatch. You can find the deceptive pairing in the Apatosaurus exhibit. Set in the floor behind the enormous dinosaur is a set of trackways—the Apatosaurus is posed as if the skeletal sauropod has just left the tracks behind. But there is no way that Apatosaurus left those tracks. The footprints and the long-necked dinosaur on display were separated by tens of millions of years.

Apatosaurus is an iconic Morrison Formation dinosaur. The hefty sauropod trod across prehistoric floodplains of America’s Jurassic West around 150 million years ago. But the footprints on display at the AMNH comes from a different time. The slab is part of a roughly 113-million-year-old trackway found along the Paluxy River near Glen Rose, Texas. Apatosaurus was long gone by the time the Texas tracks were created, and the shape of the footprints indicate that a very different kind of sauropod, probably belonging to the subgroup called titanosaurs, actually created the tracks.

Regardless of the inappropriate juxtaposition, though, getting those tracks out of the ground and set up at the AMNH was a massive paleontological undertaking. A YouTube video—posted above—shows actual footage of the 1938 excavation.

Although dinosaur tracks were known to local people since at least the beginning of the 20th century, it wasn’t until the late 1930s that the footprints garnered broad attention from paleontologists. Roland T. Bird, a fossil collector working with the AMNH, was roving the Southwest in 1937 when he got word of dinosaur tracks in the vicinity of the Paluxy River. When he got there, he found that the tracks supported a small local industry—everyone seemed to know about them, and many people had quarried tracks to sell for rock gardens. Fortunately for Bird, there were still plenty of tracks in the ground, including impressive trackways of multiple dinosaurs moving together.

The slab at the AMNH is one section of a large trackway that Bird had divided into three pieces. (The other two parts are at the University of Texas and the Smithsonian Institution.) Getting the tracks out was arduous, destructive work, made all the more complicated by the fact that at least some of the trackway went under the river. Bird and members of the local Works Progress Administration crew diverted the river to access and remove the tracks.

Bird’s tracks didn’t immediately go up on display. The broken pieces of excavated trackway just sat in the museum’s yard, and Bird’s health rapidly declined due to unknown causes and he was forced into an early retirement. When the AMNH decided to renovate its dinosaur halls in the 1940s, however, paleontologist Edwin Colbert asked Bird to come back to oversee the reconstruction of the trackway behind the museum’s “Brontosaurus” mount. Without Bird, the project would have been impossible—the broken trackway pieces were becoming exposed to the elements in the museum’s storage yard, and many of the fossil pieces were not labeled. The project was scheduled to take six weeks. Bird took six months, but, nonetheless, Bird and his collaborators were able to restore the steps of a Cretaceous giant.

Riley Black | | READ MORE

Riley Black is a freelance science writer specializing in evolution, paleontology and natural history who blogs regularly for Scientific American.