Large Mammal Skull Headed to OMSI for Cleaning, Prep Work

What do you do if you’re feeling a little old and grubby? Schedule a trip to the spa, of course, and book a makeover from top to bottom.

In the fossil conservation world, the concept is the same, but the mechanics of making it happen are a bit more complex. For one thing, it can take four strong backs and a truck just to leave home. But thanks to a collaboration with the Oregon Museum of Science and Industry (OMSI) and the North America Research Group (NARG), the Rice Northwest Museum of Rocks and Minerals recently shipped a 100-lb. fossil skull to OMSI to be prepped for eventual display here.

Fossil skull before its big move from the Rice museum curator space to the prep lab at OMSI.

First, some background. Many years ago, the museum took possession of a 34-million-year-old mammal skull from the famed Chadron Formation of South Dakota. Known at the time as a titanothere, the animal was part of a now extinct group of gigantic rhinoceros-like perissodactyls (odd-toed ungulates, or “hoofed mammals”). These behemoths roamed in herds, primarily in the Badlands area of the United States and Canada. Now usually dubbed “brontotheres“ (thunder beasts) these enormous animals were the largest North American mammals during the Eocene, standing up to 8 feet tall at the shoulder, and reaching 14 feet in length. They were so abundant during their time that entire fossil beds have been found at several locations in the Badlands area.

According to the National Park Service, brontotheres lived in open areas close to the nearly-tropical forests common in western and central North America during the Eocene. They were browsers, meaning they fed on leaves of trees or shrubs. Image from the Badlands Natural History Association.

Brontotheres were browsing herbivores with large “W” shaped molars, useful for grinding and chewing. They had a large bony “Y” shaped horn, which protruded just above the nose. The horn was much larger on males and probably used for head butting. The head was large, but the eyes were small and located on the front of the head. Ears were situated at the back. The body resembled a rhino, but the legs and feet were more like an elephant.

As brontotheres evolved, the core of their horns grew larger and longer. They had fewer incisors, which might have been related to development of a prehensile (able to grasp) lip. Their nasal canals shortened.

Most brontothere fossils are recovered from North America, although some have been found in Asia.

Connected to Famous Bone Wars

Dr. Hiram Prout, a St. Louis physician, described what was dubbed a titanothere jaw in 1846. It was the first scientifically described fossil specimen from the American West and discovered in what is now Badlands National Park. The jaw is now in the collection of the Smithsonian Institution National Museum of Nature.

The famous fossil hunters O.C. Marsh and Edward Drinker Cope gave the varied fossil titanothere-related specimens many different names, based on the shape of the horns. It turned out the horns were highly variable within a single species, and if Cope and Marsh weren’t so competitive about discovering and naming new fossils, in what became known as The Bone Wars, they might have figured the horn variability out on their own. After later paleontologists studied large collections of skulls occurring together from the same areas, they discovered that one shape actually grades into another.

Megacerops sp., North American brontothere from the Eocene. Copyright Nobu Tamara. Low res version licensed under Creative Commons Attribution.

Over time, more researchers adopted the brontothere name, but the scientific literature still retains numerous references to titanotheres, so both names are used. The key source for North American brontothere fossil remains is the Chadron Formation. According to the literature at the website of Badlands National Park, the Chadron is found in North Dakota, South Dakota, northwestern Nebraska, and eastern Wyoming. It is named after the town of Chadron, Nebraska and was mapped out by Carl Vondra in the 1950s. The greyish Chadron Formation was deposited between 34 and 37 million years ago by rivers across a flood plain. Each time the rivers flooded, they deposited a new layer on the plain. Alligator fossils indicate that a lush, subtropical forest covered the land. Most fossils found in this formation are from early mammals like the three-toed horse and the large titanothere.

Into Our Collection

This particular fossil skull came to the Rice Museum five years ago as a donation by a local dentist, who displayed the skull in his office. It was in bad shape, and the movers accidentally broke it during transport, adding further insult. A fossil preparation expert from NARG took over the skull and put in considerable time stabilizing the specimen. He also embedded a crucial metal strut under the hard palate because there was too much plaster to give any meaningful support.

The skull came back to the museum, but it still needed a lot of work before it could go on display, and volunteer help at NARG was then consumed with preparation of a recently discovered thalattosaur, a sea-going reptile discovered near Mitchell, Oregon. The skull gathered dust until recently, when it made its trip to OMSI. But now that the specimen is back in the lab, it’s time for some serious pampering.

Local fossil preparation expert Greg Carr is spearheading the project. He determined that there are three layers of restoration to update, including a coat of white paint over drywall mud and lime mortar, plus several applications of PaleoBond glue. “I plan on cleaning off the drywall mud and smoothing out the lumpy Bondo with a Dremel,” he reported. He will remove some of the lime mortar to expose as much bone as possible, but not endanger the mechanical strength.

Noted fossil prep expert Greg Carr, member of the prominent local fossil club North America Research Group (NARG) will probably need a year to prep the skull for exhibit back at the Rice Museum. Photo by Sue Wu.

“Then we’ll repaint the filled-in parts to complement the bone,” Greg said. “We’ll build a mount to hold the skull about one foot above a strong plywood base, then add lights and mirrors to highlight the wonderful teeth,” he added.

Working about one day a week, Greg estimates it could take a year to get the specimen ready for a public display.

Sue Wu, OMSI Earth Sciences Coordinator, is enthusiastic about OMSI, NARG, and the Rice Museum teaming up. “I’m excited that we can partner with the Rice Museum on this project,” she said. “There are so many great science education organizations in this area. When OMSI can collaborate with places like the Rice Museum, we provide a richer experience for our visitors. Most visitors have never heard of this fossil mammal, so this is a rare opportunity for them to see a skull being worked on. I’m grateful to the Rice Museum for providing us with this opportunity.”

She said Greg is a good choice to lead the project. “He is the perfect person to be preparing the skull. Not only is he a highly experienced fossil preparator, he’s also a fabulous educator who loves showing and sharing with visitors what he’s doing with the fossil.”

Greg and his fellow volunteers already have a nickname assigned to the skull. “Another volunteer named Jack Pollock thinks we should nickname the beast ‘Lumpy,’ Greg said. “It seems very appropriate!”

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