Since the late 1970s, the Rocky Mountain Front has been a mecca for dinosaur sleuths and researchers who have made significant discoveries about the region’s prehistoric past.
Local dinosaur resources include the Old Trail Museum in Choteau, the Two Medicine Dinosaur Center in Bynum and the Rock Shop in Bynum.
Visitors may wonder how a quiet agricultural town such as Choteau has come to be associated with one of the great dinosaur finds in the world. Well, 30 years ago a Montana geologist named Jack Horner walked into John and Marion Brandvold’s Trex Agate Shop — located in a former church in Bynum — and identified a bit of fossilized bone that has since changed the way paleontologists think of dinosaurs.
In 1978, now renowned paleontologist John R. “Jack” Horner was a “preparator” at Princeton University who had come back to Montana to do research with an old friend and Hi-Line high school teacher, Bob Makela. The two were searching for baby dinosaur bones — a rarity at that time.
John and Marion Brandvold, long-time Bynum residents, have always been amateur history buffs and, by 1978, had become pretty fair fossil sleuths on their own.
Marion Brandvold invited Horner to identify a cache of small fossilized bones she and her family had collected earlier that year in a badlands area on private property west of Choteau. Brandvold believed the fossils were those of infant dinosaurs and Horner and Makela confirmed her thoughts and found the very breakthrough they had been seeking all summer.
Marion agreed to loan them the bones for research, and they were off on the trail of the baby dinosaur.
Horner and his researchers, Marion and John Brandvold, and David and Laurie Trexler, also of Bynum, continued to dig at the site.
Eventually, the fossil hunters discovered and named Egg Mountain in the Willow Creek anticline — a series of small badlands hills that yielded the first known nests of baby dinosaurs in the Western Hemisphere, eggshell fragments and whole, fossilized eggs.
The Brandvolds and Trexlers unearthed the battered skull of an adult duck-billed dinosaur that was identified as a new species.
Horner and Makela named that adult the Maiasaura peeblesorum — the first name coming from Greek and meaning “Good mother lizard” and the second acknowledgment of the Peebles family, the local ranchers who owned the badlands up until 1987, when they sold that portion of their ranch to The Nature Conservancy. The badlands then became a part of the Conservancy’s Pine Butte Swamp Preserve. In late 2004, the Conservancy sold the property to the Bozeman-based Museum of the Rockies, which has renamed Egg Mountain as the Beatrice R. Taylor Paleontology Research Site.
The fossils were located in a portion of a rock record called the Two Medicine formation, which was created about 75 million years ago during the Cretaceous period, a span that began about 140 million years ago and ended 65 million years ago.
The formation, which covers about 3,600 square miles, is a 2,000-foot deep layer upon layer of sandstone, mudstone and shale, that contains fossils from a period of about 12 million years. The formation runs along the Rocky Mountain Front from Canada in the north, south to Augusta.
Although the Rocky Mountains were just beginning to form at the end of the Cretaceous period, the mountain front would have been located farther west than it is today, and some volcanoes may have dotted the area. Rivers flowed east from the ancestral Rocky Mountains into a vast inland seaway that stretched from the Gulf of Mexico to the Arctic Ocean, cutting North America in half.
In the Willow Creek anticline, there are four stories that can be told. The first and oldest story is that of Marion Brandvold’s discovery: nests and babies identified by Horner as belonging to Maiasaura peeblesorum.
The second story is that of a catastrophic debris flow that transported thousands of Maiasaura adult, sub-adult and juvenile bones along with many rocks, some plant material, occasional teeth, and bones from other dinosaurs.
The third story in the Willow Creek anticline is Egg Mountain, a nesting ground for the small, meat-eating dinosaur, Troodon formosus. Also found at Egg Mountain are: remains of a small plant-eater called Orodromeus makeli, complete skeletons of shrew-like mammals and varanid lizards, and an unidentified type of egg.
The fourth story is another layer of Maiasaura nests, similar to the first story mentioned above.
The Willow Creek anticline is of international significance because it is the first place in North America where baby dinosaurs were found in a nest structure, and the first place in the world where dinosaur embryos in eggs were discovered.
Horner and his research crew, along with the Brandvolds and Trexlers, made these discoveries. Horner established the existence of two new dinosaur species: Maiasaura peeblesorum and Orodromeus makeli. Research in the Willow Creek anticline continues to greatly expand scientists’ understanding of dinosaur habitat, behavior and physiology.
Horner has led the way in redrawing the perception of dinosaurs as large, sluggish reptiles with few nurturing instincts. His research supports the theory that dinosaurs were more akin to modern-day, warm-blooded, social birds. Marion Brandvold’s finds in the lower part of the Willow Creek anticline indicate that mother dinosaurs cared for their young and may have nested in colonies.
The Old Trail Museum offers exhibits and the Two Medicine Dinosaur Center (founded by the Trexlers and Brandvolds) offer individual and family paleontology experiences that can greatly enrich your vacation.
For more information on the area fossil fields, contact OTM at 406-466-5332 or the Two Medicine Dinosaur Center at 800-238-6873 or 406-469-2211.
A good resource on the discovery and development of the research is “Dinosaurs Under the Big Sky,” a book by Horner, available at OTM and other outlets in the area. This book highlights all the dinosaurs that have been discovered in Montana.
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