Two new fossils are on display at the Daniel M. Fisk Museum of Natural History. These latest additions to the museum are a “hog-like” oreodont and an ancient tortoise, both approximately 33 million years old.
The oreodont, nicknamed “Bingo,” contains approximately 30 percent real bone, Professor of Biology and museum curator Anthony Swinehart said. Swinehart found both the tortoise and the oreodont over the summer while prospecting for fossils in northwest Nebraska.
“Every year, there’s new stuff eroding out, and hopefully you catch it when it’s just starting to erode, or when there are a couple of bone fragments you spot and try to figure out where those came from,” Swinehart said.
The oreodont, so named for its “mountain teeth,” belongs to a category of prehistoric cud-chewing mammals, according to the museum display. Oreodonts were thought to be widespread in North America during the Oligocene epoch.
Swinehart said it can be difficult to spot the fossils against the ground in the badlands since both the bones and the ground are an off-white color.
Swinehart said he found a wide array of the oreodont’s bones ranging from its skull to full leg bones, ribs, and vertebrae. This allowed him to reconstruct the entire skeleton using the fossilized bones and casts based on other complete oreodont skeletons.
This particular oreodont’s teeth and some other parts of its skull will fluoresce under ultraviolet light. Swinehart said this is due to minerals in the rock formation that leach into the fossil. In this particular case, Swinehart said the minerals were most likely calcite and chalcedony, which were present in the rock formations where Bingo the oreodont was found.
Swinehart said he plans to incorporate a UV light into the display so museum visitors have an opportunity to see the fossil’s fluorescence.
“That’ll be something cool to do when we take tour groups and kids through the museum,” Swinehart said. “We can turn off the lights and shine a UV light to show them that.”
Based on the fact that many oreodont fossils are found articulated, meaning the bones are still arranged in the same position as when the animal died, Swinehart said oreodonts were most likely burrowing animals.
“It’s thought that they’re burrowers that died in their burrows, and that’s why they’re so well preserved,” Swinehart said. “They certainly have the claws for it. If something dies above ground, you have all kinds of scavengers dragging the bones around.”
Unlike the oreodont, the type of tortoise on display in the museum was most likely not able to burrow like modern tortoises can, Swinehart said.
The presence of tortoises is one piece of evidence that indicates Nebraska was most likely a sub-tropical climate while the oreodont and tortoise were alive.
Swinehart said the oreodont and tortoises would have lived in a parkland environment with open spaces interspersed with patches of forest.
Although tortoise fossils can be found from a variety of time periods as early as the age of the dinosaurs, finding well-preserved fossils can be difficult.
“Turtle shells are in lots of deposits,” Swinehart said. “The problem is that the sutures come apart really easily, so you might find lots of fossils, but they’re all tiny bits of the shell. It’s a little harder to find a nice complete one like that, because it doesn’t take much exposure to modern elements for it to become a giant puzzle, and they are the worst things to try to piece back together.”
Randall Rush ’17, who went with Swinehart last summer on the prospecting trip, said he was also able to find a few oreodont bones and two tortoises, one about six inches long and one 18 inches long.
Rush also found a jawbone from a mesohippus, a genus of three-toed primitive horse that is now extinct.
“Overall, it was a very good experience,” Rush said. “I was able to prospect in a marine cretaceous rock formation and an oligocene formation, and I had a handful of good finds at each site.”
Swinehart said the tortoise fossil also contains trace fossils, or indirect evidence of other animal life.
There also may be more bones inside the tortoise shell, but Swinehart said he did not want to risk breaking the shell to find out.
“There are little gnaw marks all over from rodents. You can see the incisors from the rodents trying to get calcium from the shell,” Swinehart said. “These are 33-million-year-old markings. Then there are some holes that may have been some larger animals with canines that tried to bite the shell.”