News Bite: The evolution of ornithischian dinosaur jaws and bites!

Edmontosaurus, Ankylosaurus, and Stegosaurus: three ornithischians with very different bites!

With Past Time, Matt and I tend to focus on the new discoveries in paleontology: the new species that show up in the news, or the important specimens discovered in museum collections. These are the raw materials that feed the fires of paleontology as a science. However, observation is only the first step in the scientific method: a method that paleontologists follow.

This week’s episode features the work of Dr. Ali Nabavizadeh, a postdoctoral researcher at the University of Chicago. Ali recently completed a Ph.D. studying the functional anatomy of dinosaur jaws at Johns Hopkins University. His work combines a knowledge of modern reptile jaw muscles and tissues and the skeletons to dinosaurs to make two-dimensional models that can estimate the relative differences in the bite forces of extinct animals. Ali’s research takes those initial observations (the fossils themselves) and uses them to estimate the actual biology of dinosaurs.

His research also asks specific questions about the storied history of Ornithischia, the dinosaur group that includes Triceratops, Stegosaurus, the duck-billed hadrosaurs, Iguanodon, and virtually every herbivore that wasn’t a long-necked sauropod. These animals wrote the book on eating plants during the 150+ million year reign of the dinosaurs, and they had a huge variety of different jaw constructions and tooth shapes. Using relative bite force estimates from over 50 ornithischian dinosaur species, Ali estimated where major changes in the force of the bites and the position of the strongest bite within the jaw occurred in dinosaur evolution. Although many paleontologists have sought to understand the jaw muscles of dinosaur groups, Ali’s research is special in the sheer number of species he examined at once! His research therefore proposed a hypothesis, that the bite forces of different groups of ornithischian dinosaurs were very different.

Ali then mapped the relative dinosaur bite forces onto a tree of relationships, to see whether or not there were major shifts and where those occurred. He indeed found that some groups had quite different bites than others; the armored dinosaurs (stegosaurs, ankylosaurs) were not strong biters, while the duck-billed hadrosaurs and giant ceratopsians were very strong biters, especially at the backs of their jaws. The data strongly support the hypothesis that major groups of ornithischian dinosaurs experimented with a wide array of different biting strategies in their inexorable search for food.

Research like this is a great example of that “next step” that Past Time hasn’t really highlighted as much. The fossils sit in museums for a reason: so that researchers can pick them back up to try and answer their own questions about the past. With research on dinosaur jaw mechanics, we have a chance to not only understand how individual species approached food processing; we can also try to answer questions about how those capabilities evolved over time. Did they maintain the same bite forces? Did they alter their jaw anatomy to effect a stronger bite? Only by taking the fossils to the next step—by using them to ask and answer new questions about ancient biology and evolution—can we truly begin to understand past time.

For more information, check out Ali’s website: https://sites.google.com/site/alinabav/

Also, follow him on twitter @vert_anatomist!

Filed under: Dinosaurs, Fossils, Functional Morphology, Paleontology, feeding, jaws

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