By Abby Telfer, FossiLab Manager, Paleobiology Department
For the last year and a half, a volunteer in the National Museum of Natural History’s FossiLab has been practicing slow motion dentistry on some amazing teeth. My dentist would be appalled by how long the job is taking, but she has never had to stare down molars this large or clean tartar buildup anywhere near as thick and hard as the rock matrix that’s hugging these monsters.
The teeth belonged to a brontothere, a type of mammal related to horses and rhinoceroses, that went extinct about 35 million years ago. They were preserved along with the upper jaw and part of the skull. The lower jaw is missing, as is most of the rest of the skeleton.
Paleontologists reported the first brontothere fossil discoveries in the 1870s. Since then, thousands of specimens have been collected in North America and Asia, allowing scientists to document the many ways that brontothere species changed over their 20 million years of evolutionary history. Early species were small and lacked horns, but some later species evolved to be as large as elephants and sported horns and other bony protuberances on their snouts that would make a modern rhino proud.
A long layover
Most Fossilab projects support the ongoing research of the Museum’s paleontologists, who explore fossil sites around the world. Even when collected in very remote places, the fossils usually arrive at FossiLab within a few months. The brontothere is unusual; its trip from South Dakota took more than 110 years.
In the early 1880s, Spencer Baird, the Smithsonian’s second Secretary, asked a Yale University professor of paleontology named O. C. Marsh to collect vertebrate fossils for the newly-built United States National Museum. A series of expeditions out west yielded a trove of Jurassic dinosaurs and Eocene mammal fossils that Marsh shipped to Yale for preparation and study. Eventually, a spectacular array of fossils, filling more than seven railroad cars, was sent to Washington. Included were dinosaurs, Stegosaurus, Allosaurus, and Triceratops among them, and more than 150 brontothere skulls. But the block of rock containing the FossiLab brontothere was overlooked and forgotten. So while the dinosaurs have been on display almost continuously since the National Museum of Natural History opened in 1910, and the brontotheres have been available for study in our collections, the FossiLab brontothere lingered in obscurity. The 1990s brought its rediscovery and shipment to Washington. Now, in FossiLab, it is making a slow motion debut.
Rock matrix is removed from the bones and teeth with small picks and a tool called an air scribe - a mini-jackhammer, really. The air scribe’s pointed tip makes high frequency impacts against the hard matrix, causing tiny bits of rock to fly off the chocolate-brown teeth and white bone. This speeds the work, but, still, progress is slow because enormous care is needed to avoid touching the tip to tooth or bone. Fortunately, the patient complains as much about the slow pace of cleaning as it does about the century-long wait for its dental appointment, which is to say, not at all!