It’s a dinosaur legend that pachycephalosaurs—bipedal, Cretaceous beasts with massive, thick domed skulls—today make big-butting heads like bighorn sheep. But new analysis shows that this is far from the case; rather, pachycephalosaurs (pack-ee-SEH’-fa-low-sawrs) may have moved more like kangaroos, using their tails as a tripod that could prop them up while delivering powerful kicks to opponents.
Paleontologists found evidence of this kickboxing behavior by analyzing a well-preserved skeleton of Pachycephalosaurusmaking a virtual 3D model of it and noting that parts of dinosaurIts anatomy resembled that of a kangaroo and it moved in a strikingly similar manner.
“The skeleton in our study confirms that they used their tails for support, as kangaroos do, but not that they ran against each other and bumped their heads against each other like bighorn sheep [do]Kari Woodruff, the curator of vertebrate paleontology at the Frost Museum of Science in Miami, who led the study, told Live Science.
The research was presented Nov. 2 at the Society of Vertebrate Paleontology’s annual conference in Toronto and has not yet been published in a peer-reviewed journal.
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Pachycephalosaurs are the poster children for weird-looking dinosaurs. “They have this big bowling ball on their head,” Woodruff said. “They have these really pointy, carnivorous dinosaur-like teeth in the front of their mouths, but they ate plants. Everything about them is strange.”
For a long time it was believed that these Cretaceous period (145 million to 66 million years ago) freaks ran at each other and bumped their melon heads, possibly to compete for mates, food, or territory. And while several paleontologists have challenged this mind-boggling idea over the past two decades, it remains a popular concept.
Although many paleontologists have studied pachycephalosaur skulls, analysis of the rest of the body is scarce because their skeletons are rarely well preserved, Woodruff said. But, access to well preserved Pachycephalosaurus wyomingensis specimen from the Hell Creek Formation of the American West meant that Woodruff could examine its spine as well as other anatomical features that might offer clues to its behavior.
After using a laser scanner to create a virtual 3D model of P. Wyomingensis, Woodruff focused on the dinosaur’s strange hind vertebrae, which had ridged ends—almost as if someone had placed two ridged potato chips at either end of each vertebra. Those ruffles fit perfectly, like a stack of potato chips, Woodruff noted. Paleontologists previously suggested that these ridged vertebrae aid in head banging, possibly distributing the forces of high-velocity head impacts, Woodruff said.
But when Woodruff and his colleagues examined the skeletons of other head-butting animals, including bighorn sheep, muskox and deer, none had frayed vertebrae; however, the kangaroo did.
The new study supports the hypothesis, first formulated in the 1970s, that pachycephalosaurs may have used their tails for support, like kangaroos. That’s because P. Wyomingensis shares several anatomical features with the kangaroo – not only the vertebrae, but also the pelvis and tail.
Pachycephalosaurs may even have engaged in kickboxing-like behavior. When a kangaroo kicks, they do so from a tripod position, with the tail supporting some of their body weight. “To kick, the kangaroo has to first lean back on its tail, and once it’s propped up, then it can kick,” Woodruff said.
Although this is only a hypothesis, “there is a possibility that [pachycephalosaurs] could exhibit their own form of kickboxing-like behavior,” he said.
But in addition to kickboxing, did pachycephalosaurs bang their iconic heads together? If they did, it probably wasn’t at high speeds, given that their anatomy doesn’t resemble that of bumpy animals, Woodruff said. Perhaps pachycephalosaurs were more like big cows that didn’t charge each other, but sometimes pushed into each other at low speeds. “If — and it’s a big if — pachycephalosaurs used their heads to fight each other,” Woodruff said, then they were probably “sumo wrestlers, not competitors.”
Although this SVP presentation offers promising evidence of dinosaur kickboxing behavior, a peer-reviewed and published study will likely reveal more details, said Joseph Peterson, a paleontologist and pachycephalosaur expert at the University of Wisconsin Oshkosh who was not involved in the research. “This has the potential to really change the way we look at these particular animals,” Peterson told Live Science.
And while the findings are surprising, they just add to the general weirdness of pachycephalosaurs. “These are really strange animals,” Peterson said. “It adds a new dimension to it.”