Meet ‘Junior,’ the Giant Bison Skull That Crossed the Country to Star in New Exhibition at the National Museum of Natural History

The colossal cranium from Idaho recently received a touch-up to prepare for the Smithsonian spotlight

When the National Museum of Natural History’s new exhibition “Bison: Standing Strong,” opens on May 7, visitors will learn about the rise, fall and resurgence of the national mammal. This epic tale is brought to life through several specimens and objects, including a mounted bull bison and bison-related objects from Indigenous communities, including artwork, traditional tools and even a toy fashioned out of the animal’s woolly fur.

Another showstopping specimen featured in the exhibition is a six-foot-wide skull of Bison latifrons, a prehistoric species of bison that lived during the Late Pleistocene Epoch between 120,000 and 13,000 years ago. The colossal cranium, nicknamed ‘Junior,’ is on loan to the Smithsonian from the Idaho Museum of Natural History (IMNH) courtesy of the Bureau of Reclamation.

Junior and other specimens in the exhibition help tell the story of how bison became central ecological players on North America’s plains. During the Pleistocene between 195,000 and 135,000, the ancestral steppe bison (Bison priscus) trudged across the Bering Land Bridge and into North America.

Ancient bison proliferated on the new continent into several species. One such species was Bison latifrons, or the long-horned bison, a gargantuan grazer that boasted curved horns that could stretch more than seven feet across. B. latifrons was roughly 25% larger than living plains bison and ranged across much of the continent from Florida to California and Mexico through southern Canada.

Idaho was once prime habitat for B. latifrons, which roamed the Snake River Plain, a high-elevation expanse nestled between mountains that covers around a quarter of the state. During interglacial periods of the Pleistocene, the area’s open plains were ice-free and also home to ancient horses, camels and mammoths.

The fossilized remains of these ice age animals are often found along the banks of the Snake River. As the waters fall and rise each season, the bones erode out of the surrounding rocks and are washed toward nearby dams, including the American Falls Reservoir that is located only 25 miles from IMNH’s location in Pocatello, Idaho. The U.S. Bureau of Reclamation manages these dams to maintain the region’s agricultural water supply and deposits any fossils found in the reservoirs into the collection at IMNH. The Bureau has also helped fund efforts to digitize several of B. latifrons specimens.

One of the most notable specimens in IMNH’s collection is Junior. In 1948, the substantial skull was unearthed near the American Falls Reservoir by Marie L. Hopkins, the state’s first female paleontologist. During her decades-long tenure as a curator at IMNH, Hopkins led efforts to excavate the Late Pleistocene fossils from Snake River sites, providing the museum with a detailed snapshot of this time period.

At the time, Junior provided the most complete look at B. latifrons (another skull at IMNH discovered in the early 1950s and nicknamed Mary Lou is slightly more complete). Previous specimens of the species mostly consisted of massive sets of horns. More fragile elements of the skull, such as eye sockets and snouts, were often fractured or missing altogether.

Hopkins described the skull in detail in 1951 in the Journal of Mammalogy before Junior went on display in IMNH’s fossil exhibit for nearly 75 years. The fossil, and the species it represents, even inspired the museum’s logo.

When the exhibition team at the National Museum of Natural History approached IMNH about featuring a B. latifrons skull in the new exhibit, Brandon Peecook, the curator of paleobiology at IMNH, knew there was only one logical choice. “Junior is the one to send to D.C. because it’s undamaged and beautifully preserved,” Peecook said.

The NMNH exhibition team agreed that Junior would be an ideal fit and also received approval from the U.S. Bureau of Reclamation, which owns the fossil. In late 2025, Peecook and his colleagues carefully removed Junior from the metal brackets that had supported its dense dome for three quarters of a century. They then placed the skull in a form-fitting, plaster and fiberglass storage cradle that encased the skull like the interlocking shells of a clam. The cradle was packed into a large wooden crate, loaded onto a truck and transported cross country by FedEx Custom Critical and FedEx Cares to the Smithsonian.

On December 9, the FedEx truck transporting Junior pulled into the National Museum of Natural History’s parking lot where several Smithsonian staff members, including fossil preparator Michelle Pinsdorf, were waiting to greet it. The team gingerly unloaded the crate containing the skull with a pallet jack.

Once off the truck, the team moved the fossil through the museum on a wheeled cart — thankfully the building was built to accommodate large specimens and objects, Pinsdorf said — to one of the museum’s fossil preparation labs. This month, specialists from Research Casting International (RCI), a company that creates casts and mounts of fossils, including several in the museum’s “Deep Time Hall of Fossils,” is giving Junior a slight touch up before its debut when the exhibition opens in early May.

Even before the prep work began, Pinsdorf and other museum staff members were able to see a side of Junior that few have seen. The fossil skull had long been displayed top-side-up with its massive curved horns pointing out. This obscured the bottom of the specimen, including the battery of teeth that Junior used to grind grasses and other plant material.

The grazing was not always easy. As Pinsdorf and her colleagues examined the skull, they noticed that one side of the jaw was missing a tooth. “This bison must have had a serious toothache at some point,” Pinsdorf said. “For an animal that spent so much of its life chewing, recovering from a missing tooth would have been tough.” Junior was a durable bovine, though. The missing tooth is surrounded by healed bone, revealing that the giant bison survived the dental damage.

“Being able to see evidence of an individual animal's life story after so many years is what makes paleontology exciting for me,” Pinsdorf said. She thinks every fossil tells a unique tale and is excited for museum staff and visitors alike to become familiar with Junior’s story when the skull goes on display in May.

Peecook agrees and looks forward to visiting the exhibit himself this summer. He knows that Junior is ready for the limelight that comes with a prominent perch in the nation’s capital. “All the people coming through the mall and museum this summer are going to see Junior, the most beautiful of all of our bison,” Peecook said. “This skull is the perfect way to bring our museum in Pocatello to the nation.”

Jack Tamisiea | | Read More

Jack Tamisiea is a Science Communications Specialist at the Smithsonian's National Museum of Natural History. In addition to covering all things natural history for the museum's blog, Smithsonian Voices, he tracks media coverage and coordinates filming activities for the museum's Office of Communications and Public Affairs. Jack recently completed his masters in science writing at Johns Hopkins University and his writing has appeared in the New York Times, Scientific American, National Geographic and other science-focused publications. In his free time, he loves exploring the outdoors with a sketchbook and camera. You can read more of Jack's work at https://jacktamisiea.com.