History of Paleontological Research in the Bridger Formation


Looking southwest at Grizzly Buttes, a set of badland exposures in the lower Bridger Formation (stratigraphic subdivision B) popular with early fossil collectors. The area is located south of the towns of Lyman, Mountain View and Fort Bridger, Wyoming.

Bridger Formation fossils have been collected and studied by paleontologists for over 135 years. Trapper Jack Robertson, who found what he reported to be a “petrified grizzly bear” in the 1860’s, is reputed to be the first collector of a fossil from the Bridger. This led to the use of the name “Grizzly Buttes” for a particularly fossiliferous set of badlands near Fort Bridger, Wyoming. The fossil was probably a brontothere skull.

The Bridger Formation was named the “Bridger Group” in 1869 by U.S. government explorer F.V. Hayden during the U.S. Geological and Geographical Survey of the Territories. Fossils collected during the Hayden survey were sent to paleontologist Joseph Leidy in Philadelphia for study. In 1869, Leidy, who is often regarded as the father of North American paleontology, published the first scientific account of a Bridger fossil in which he described the small tarsioid primate Omomys carteri. The species was named after Leidy’s friend Dr. J. Van A. Carter, who lived at Fort Bridger and sent the fossils he discovered in the Bridger badlands to Leidy for study.

Lateral view of skull of the enigmatic herbivorous mammal Loxolophodon cornutus (=Eobasilieus cornutus) described and figured by paleontologist E.D. Cope (1872).

The Yale College Expedition of 1870, with paleontologist O.C Marsh standing at center.

The early reports of fossils in the “Bridger country” did not go unnoticed by rival paleontologists Othniel Charles Marsh and Edward Drinker Cope, both of whom led fossil collecting expeditions to the area in the early 1870’s. Their efforts resulted in a flurry of often hastily prepared scientific papers with each man racing to describe more fossils than the other. The rivalry between these two men, which so disgusted Joseph Leidy that it led to his abandonment of paleontology, lasted for more than thirty years, and is popularly known as the “bone wars.” Early fossil collecting expeditions in the Bridger badlands resulted in large fossil collections at the Philadelphia Academy of Natural Sciences (Leidy), Yale University (Marsh), the American Museum of Natural History (the AMNH purchased Cope’s collection just prior to the turn of the century), and Princeton University (H.F. Osborn, W.B. Scott, and F. Speir).

Collecting from the American Museum of Natural History from 1903 to 1906, Walter Granger and William Diller Matthew initiated the first scientific fossil collecting program in the Bridger Formation by mapping and naming widespread layers of light-colored resistant rocks, which he named “white layers.” These layers are actually limestone beds which formed in ancient lakes and ponds. By tracing these beds across the badlands, and figuring out the relative positions of fossil localities, the paleontologists could tell which fossils were older or younger than others. By mapping some of these layers, they extended their stratigraphic framework across the basin, describing their fossil localities relative to Matthew’s named “marker beds.” W.D. Matthew’s pioneering stratigraphic work was described in his classic 1909 monograph entitled The Carnivora and Insectivora of the Bridger Basin.

The American Museum of Natural History's field camp along Leavitt Creek southeast of Fort Bridger, 1905.

Looking southwest at exposures of the upper Bridger Formation (mostly subdivision D) on "Old Hat Mountain," a butte adjacent to Hickey Mountain near the Lonetree Divide. The butte is capped by Bridger E, and the ledge just below the uppermost peak is supported by the Upper White Limestone (W.D. Matthew's Upper White Layer).


Other paleontologists who made important contributions to research in the Bridger Formation during the twentieth century include C.L. Gazin of the Smithsonian Institution (1941-1968), P.O. McGrew and R. Sullivan of the University of Wyoming (1960’s), and R.M. West of the Milwaukee Public Museum (1970’s). Recent and current work is being conducted by researchers from the San Diego Natural History Museum, University of Colorado Museum of Natural History, Denver Museum of Nature and Science, Loma Linda University, and the University of Michigan Museum of Paleontology.


Map of the Bridger Basin Project study area showing both modern and historical geographic terminology. Green areas indicate approximate locations of upper slopes of major mountains in the area, while black lines outside of green areas represent approximate elevations of lower slopes. The study area includes most rocks of the Twin Buttes and Turtle Bluffs members.

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