Seventy-Seven Million Years in Phillips County:

The Discovery, Science, and Legacy of Montana's Leonardo

The Discovery

On the last day of a summer expedition in the badlands of northern Phillips County, Montana, a North Dakota physician named Dan Stephenson spotted a reddish discoloration in the face of a low cliff. The mark, visible from a short distance, resembled an X-ray image of a pelvis. Stephenson, who had joined a volunteer dig organized by the Judith River Dinosaur Institute, recognized what he was looking at. It was July 2000, and the field season was nearly over. What he had seen, partially eroding from a channel sandstone deposit within the Late Cretaceous Judith River Formation, would prove to be among the most scientifically significant paleontological finds in recorded history.

The specimen was a Brachylophosaurus canadensis, a member of the hadrosaurid family of plant-eating dinosaurs that inhabited the coastal floodplains of what is now central Montana approximately 77 million years ago. This particular animal, however, was exceptional from the first moments of its excavation: it was, to a degree no previously discovered dinosaur had been, preserved not merely as bone but as a body. Across roughly 90 percent of its skeletal surface, the fossil retained mineralized impressions of soft tissue, including skin, scales, muscle mass, foot pads, and beak material. Even the stomach region appeared to contain the remnants of a final meal. When the field team formally named the specimen, they turned to a piece of graffiti cut into a nearby sandstone outcrop. Sometime around 1917, a Montana cowboy named Leonard Webb had carved his name, the date, and the name of his girlfriend, Geneva Jordan, into the rock. The team initially called the dinosaur "Leonard," found that too casual, and settled on "Leonardo" (Dinosaur Mummy CSI: Guide to the Dinosaur Mummy, dinosaurmummy.org, accessed 18 Apr. 2025).

The Geological Context

To understand why Leonardo exists, it is necessary to understand the Judith River Formation, the geological unit in which the fossil was entombed. During the Campanian stage of the Late Cretaceous period, the interior of North America was divided by a shallow body of water known as the Western Interior Seaway. Eastern Montana at that time bore a resemblance to the present-day Mississippi Delta region: a warm, humid coastal environment laced with rivers, wetlands, and dense conifer forests, lying at low elevation near the margin of the retreating sea. The Judith River Formation, composed primarily of mudstones, siltstones, and channel sandstones deposited by that ancient river system, has yielded an extraordinary concentration of dinosaur material across the Hi-Line region of north-central Montana. Phillips County, which encompasses the area around the town of Malta, sits at the heart of some of the most productive fossil-bearing outcrops in North America (Phillips County Museum, Montana Dinosaur Trail, mtdinotrail.org, accessed 18 Apr. 2025).

Within this formation, Brachylophosaurus canadensis was among the dominant large herbivores. The species is distinguished by a relatively flat, paddle-like bony crest extending over the rear of the skull, shorter than the elaborate crests of some related hadrosaurs. Adults could reach lengths of approximately 35 feet, though Leonardo, who died as a subadult estimated to be around three to six years old, measured roughly 23 feet from snout to tail. Brachylophosaurus specimens in various states of preservation had been recovered from the Judith River Formation since the 1980s and 1990s, including a nearly complete individual nicknamed "Elvis" found by Nate Murphy in 1994, which remained on display at the Phillips County Museum in Malta. Leonardo, however, represented a category of preservation that paleontologists had never before encountered in the modern era of the discipline.

The Excavation

The full excavation of Leonardo took place over the summer of 2001, led by Murphy, who served as curator of paleontology at the Phillips County Museum and as the director of the Judith River Dinosaur Institute. Murphy, a self-taught fossil hunter who had spent decades working the badlands of north-central Montana, had assembled a team of professional and amateur paleontologists to extract the specimen from its canyon wall matrix. The challenge was considerable. Leonardo's body was embedded deeply in a channel sandstone deposit, and to remove the fossil intact required removing an enormous surrounding block of rock. A demolition crew employed explosives to detach an 18-foot section of cliff face, yielding a block estimated to weigh 6.5 tons. The fossil was subsequently insured for $2.5 million during transport for analysis (HowStuffWorks, "What's So Special About a Dinosaur Named Leonardo?," science.howstuffworks.com, accessed 18 Apr. 2025).

The excavation's difficulty was compounded by the unusual nature of what the team was uncovering. Because Leonardo was not simply a skeleton but what researchers described as a natural mold of the animal's body in the surrounding stone matrix, standard excavation procedures had to be modified to avoid damaging the integument impressions covering the bones. The process of extraction took more than nine weeks and involved more than twenty diggers. The resulting specimen was assigned the collection number JRF 115 and catalogued as part of the holdings of what would become the Great Plains Dinosaur Museum in Malta, a nonprofit institution established in 2002 by the Judith River Foundation.

The Science of Preservation

How Leonardo achieved its remarkable state of preservation remained a subject of investigation in the years following the excavation. The prevailing interpretation, derived from taphonomic analysis of the burial setting, involves a specific sequence of environmental circumstances unlikely to be repeated. Murphy and colleagues proposed that Leonardo likely died near a waterway and that, before extensive decomposition could occur, floodwaters inundated the carcass and deposited silt around it. As the waters receded, the body was left submerged in a shallow, stagnant pool laden with decomposing conifer branches, the same conifers that would later be found as fragments in Leonardo's gut region. Aldehydes produced by decomposing conifer material, chemically similar to the preserving agents used in ancient Egyptian embalming, are thought to have leached into the carcass, retarding bacterial decay. This chemical preservation, repeated over what may have been a series of seasonal flood events spanning decades, allowed the body to desiccate and mummify rather than rot. Gradual fossilization then replaced the preserved organic tissue with minerals, producing the extraordinary integument impressions that survived for 77 million years (Dinosaur Mummy CSI: Guide to the Dinosaur Mummy, dinosaurmummy.org, accessed 18 Apr. 2025).

Murphy, David Trexler, and Mark Thompson provided the first formal scientific description of Leonardo in a 2006 chapter published in the Indiana University Press volume Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs, edited by Kenneth Carpenter. Their treatment established the taxonomic identification, described the preservation in systematic detail, and laid the foundation for the subsequent research program that would engage scientists from multiple institutions over the following decade (Murphy, N. L., D. Trexler, and M. Thompson. "'Leonardo,' a Mummified Brachylophosaurus from the Judith River Formation." Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs, edited by Kenneth Carpenter, Indiana University Press, 2006, pp. 117-133).

In 2004, the Guinness Book of World Records recognized Leonardo as the best-preserved dinosaur ever documented, a distinction that brought international attention to the specimen and to the small city of Malta, Montana.

Scientific Analysis

Because the fossil preserved not merely bones but the outline and texture of the animal's body, researchers faced methodological challenges without direct precedent. A traditional physical investigation of the fossil's interior would have required destructive sampling, risking damage to an irreplaceable specimen. The team behind the Leonardo Project instead pursued a program of non-invasive imaging, moving the fossil to NASA's Johnson Space Center Ellington Field facility in Houston, Texas, where more than forty X-ray images were taken using equipment capable of penetrating the dense rock matrix. Teams from Kodak and Carestream Health joined NASA specialists to conduct digital scanning that allowed researchers to reconstruct internal anatomy in three dimensions without disturbing the original material. The resulting data produced the most detailed internal picture of a non-avian dinosaur yet assembled.

The stomach contents proved especially informative. In 2008, Justin S. Tweet, Karen Chin, Dennis R. Braman, and Nate L. Murphy published an analysis of the material concentrated in Leonardo's gut region in the peer-reviewed journal PALAIOS. Examining the taphonomy of the carcass and the organic remains in the body cavity, they identified abundant plant fragments concentrated within what appeared to represent the digestive tract, providing what they described as the second well-substantiated case in which the gut contents of a plant-eating dinosaur had been documented. Analysis of pollen and plant material in the gut region revealed a variety of vegetation types including ferns, conifers, and flowering plants such as magnolias, indicating that Brachylophosaurus was a generalist browser that consumed available plant material across the landscape (Tweet, Justin S., et al. "Probable Gut Contents Within a Specimen of Brachylophosaurus canadensis (Dinosauria: Hadrosauridae) from the Upper Cretaceous Judith River Formation of Montana." PALAIOS, vol. 23, no. 9, 2008, pp. 624-635. doi:10.2110/palo.2007.p07-044r).

The scientific program generated further findings in subsequent years. In 2016, Tweet, Chin, and A. A. Ekdale published a study in the Journal of Paleontology identifying what they interpreted as trace fossils of possible parasites within the same gut contents region. Needle-like worm traces covered in fine bristles were identified in the stomach area, providing the first fossil evidence of internal parasites in a dinosaur and suggesting that hadrosaurs, like many modern animals, hosted gut fauna as part of their normal biology (Tweet, Justin, Karen Chin, and A. A. Ekdale. "Trace Fossils of Possible Parasites inside the Gut Contents of a Hadrosaurid Dinosaur, Upper Cretaceous Judith River Formation, Montana." Journal of Paleontology, vol. 90, no. 2, 2016, pp. 279-287).

Controversy and Legacy

Leonardo's prominence brought public attention to the Judith River Dinosaur Institute and to Nate Murphy, who became a recognizable figure in popular paleontology. Murphy appeared in publications including Newsweek and National Geographic and was featured in a 2008 Discovery Channel documentary titled Secrets of the Dinosaur Mummy. He cultivated a public identity as what journalists described as the "people's paleontologist," and the Leonardo find elevated Malta into an unlikely destination for scientists, documentary crews, and tourists from around the world.

The subsequent years, however, revealed serious complications in Murphy's professional conduct. Beginning around 2007, state and federal investigators examined allegations that Murphy had removed dinosaur fossils from public lands without permits. The Billings Gazette published a four-part investigative series in which former colleagues described both scientific irregularities in Murphy's field methods and biographical fabrications in his public presentations. In 2009, Murphy entered a guilty plea on federal charges related to fossil theft from Bureau of Land Management land. The case drew national attention to the ongoing tension in American paleontology between commercial fossil hunting, amateur collection, and the requirements of publicly accountable science. Murphy's legal difficulties did not affect the scientific validity of the Leonardo find itself, which had been excavated from private ranch land, but they complicated the institutional history surrounding the specimen and the organizations that had formed around it (Billings Gazette, "Discovery and Deception: Spectacular Finds, Criminal Charges," billingsgazette.com, accessed 18 Apr. 2025).

The Great Plains Dinosaur Museum, which opened in Malta in 2007 under the governance of the Judith River Foundation after its separation from Murphy, continued to operate as the primary institutional home of the Leonardo specimen and as an anchor of paleontological tourism in northeastern Montana. The museum maintains a rapid-prototype replica of Leonardo on permanent display; the original fossil has traveled on loan to major institutions including the Houston Museum of Natural Sciences and, as of 2025, the Fukui Prefectural Dinosaur Museum in Japan (Great Plains Dinosaur Museum, "Leonardo," greatplainsdinosaurs.org, accessed 18 Apr. 2025; Earth Science Guy, "#87 - Montana's Famous 'Mummified' Dinosaur," earthscienceguy.com, accessed 18 Apr. 2025).

Conclusion

Leonardo remains the most complete mummified non-avian dinosaur specimen ever documented, and the scientific literature it has generated continues to shape understanding of hadrosaurid biology, Late Cretaceous ecology, and taphonomic processes. The specimen's origin in the Judith River Formation of northern Phillips County places it within a geological and cultural context that has made Malta one of the most consequential sites in North American vertebrate paleontology. The graffiti that gave the dinosaur its name was carved by a Montana cowboy in the badlands nearly a century before the fossil's discovery. The confluence of those two moments, the cowboy's chisel in 1917 and the physician's eye in 2000, encapsulates something characteristic of Montana's relationship to its deep past: the land holds what it holds, and the surface occasionally gives it up.

Works Cited

Great Plains Dinosaur Museum and Field Station. "Leonardo." greatplainsdinosaurs.org/leonardo/. Accessed 18 Apr. 2025.

Dinosaur Mummy CSI. "Guide to Dinosaur Mummy CSI - Leonardo the Dinosaur Mummy." dinosaurmummy.org/guide-to-dinosaur-mummy-csi.html. Accessed 18 Apr. 2025.

Earth Science Guy. "#87 - Montana's Famous 'Mummified' Dinosaur." earthscienceguy.com/2025/12/87-montanas-famous-mummified-dinosaur.html. Accessed 18 Apr. 2025.

Montana Dinosaur Trail. "Phillips County Museum." mtdinotrail.org/phillips-county-museum/. Accessed 18 Apr. 2025.

Murphy, N. L., D. Trexler, and M. Thompson. "'Leonardo,' a Mummified Brachylophosaurus from the Judith River Formation." Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs, edited by Kenneth Carpenter, Indiana University Press, 2006, pp. 117-133.

Tweet, Justin S., Karen Chin, Dennis R. Braman, and Nate L. Murphy. "Probable Gut Contents Within a Specimen of Brachylophosaurus canadensis (Dinosauria: Hadrosauridae) from the Upper Cretaceous Judith River Formation of Montana." PALAIOS, vol. 23, no. 9, 2008, pp. 624-635. doi:10.2110/palo.2007.p07-044r.

Tweet, Justin, Karen Chin, and A. A. Ekdale. "Trace Fossils of Possible Parasites inside the Gut Contents of a Hadrosaurid Dinosaur, Upper Cretaceous Judith River Formation, Montana." Journal of Paleontology, vol. 90, no. 2, 2016, pp. 279-287.

Billings Gazette. "Discovery and Deception: Spectacular Finds, Criminal Charges." billingsgazette.com/news/state-and-regional/montana/discovery-deception-spectacular-finds-criminal-charges/article_3135e99b-7c7e-51a7-a7f0-975d770ad079.html. Accessed 18 Apr. 2025.