One Hip Dino

As was common during his trips home, he was showing a friend, Auburn University comparative anatomist Ray Wilhite, around the museum’s collections. Upon noticing a bizarrely shaped ilium, or hipbone, in the collection, Wilhite told Wedel that he “ought to take a closer look,” Wedel recalls.

A new thunder-thighed dinosaur species emerges from a pile of bones in Oklahoma.

The next year, Wedel photographed the bones and started looking at them in more detail, and he realized that Wilhite was right—the ilium bone was unlike any dino hip he’d ever seen. His efforts got put on hold for a few more years while he finished his dissertation, but when the opportunity arose to return to the project, Wedel jumped on it. He teamed up with Michael Taylor, a paleontologist at University College London who was stateside for a conference in Austin, Texas, and the two of them spent the better part of a week inspecting the bones.

“The real question wasn’t so much whether we had something new, but how many ‘something new’s we had,” Taylor says. In addition to the peculiar ilium, there was also an unusual shoulder bone that appeared to be from a much larger animal. After careful analysis and reconstruction, they concluded that the bones were most likely from two different individuals, possibly an adult and a juvenile, of a single new sauropod genus and species.

Taylor, Wedel, and Wedel’s museum mentor Richard Cifelli posited that the abnormal ilium was formerly connected to an especially large, muscular thigh, possibly used in male competition for females, or for powerful self-defense kicks. They named the new species Brontomerus mcintoshi—Brontomerus translates to “thunder thighs,” and mcintoshi honors John Stanton McIntosh, a retired physicist and North American sauropod guru (Acta Palaeontol Pol, 56:75-98, 2011). According to Wedel, unusual bumps on the shoulder blade suggest that the species may have also had powerful forelimbs, making it quite athletic and well suited to clamber through its hilly Cretaceous habitat.

But not everyone is convinced that the strange bones warrant the distinction of a new genus and species. “The ilium projects forward by 55 percent, while in other species it’s 52 percent, [but] that measure can vary by more than 3 percent,” says Mike D’Emic, a PhD candidate in paleontology at the University of Michigan. “In paleontology it’s difficult to separate individual variation—variation due to gender or variation due to age—from taxonomically meaningful variation.”

Furthermore, adds paleontologist Susannah Maidment of the Natural History Museum in London, the estimation of the ilium’s projection “is based on one partial bone. It’s very, very fragmentary.” To be more convincing, she says, it might be helpful to perform three-dimensional analyses using laser scanning techniques to reconstruct how the muscles might have attached.

Unfortunately, a paucity of fossils is a common problem with Cretaceous sauropods, Wilhite notes. “Almost every one of them is based on partial material and in many, many cases the parts don’t overlap,” he says.

Given the rarity of sauropod specimens from the Early Cretaceous, Brontomerus mcintoshi could help fill a lingering gap in the fossil record. “It is an important contribution to our understanding of North American dinosaurs and how the sauropods as a group changed going from the Jurassic into the Cretaceous,” says Maidment.

Wedel, now at Western University of Health Sciences in Pomona, California, continues to work his way through other piles of dinosaur bones that may be harboring new species and new insights into dinosaur evolution. “As people have said before,” says Wilhite, “some of the best new dinosaurs have been found in the basements of museums.”