Members of Theropoda, the only clade of predominantly predatory dinosaurs, were successful predators partly due to a unique, deeply serrated tooth structure that allowed them to easily tear through the flesh and bone of other dinosaurs, according to a new study published in the journal Scientific Reports.

The teeth of theropod dinosaurs are characterized by ziphodonty, the presence of serrations on their cutting edges. The only reptile living today that has the same superficial tooth structure is the Komodo dragon (Varanus komodoensis).

“What is so fascinating to me is that all animal teeth are made from the same building blocks, but the way the blocks fit together to form the structure of the tooth greatly affects how that animal processes food. The hidden complexity of the tooth structure in theropods suggests that they were more efficient at handling prey than previously thought, likely contributing to their success,” said Dr Kirstin Brink from the University of Toronto Mississauga, who is the first author on the study.

Dr Brink and co-authors found that the unique arrangement of tooth tissues did not develop in response to these carnivores chewing hard materials.

They determined this by examining samples of dinosaur teeth that had not yet broken through the gums, as well as samples from mature dinosaur teeth. Unlike humans, reptiles grow new teeth throughout their lifetimes.

“What is startling and amazing about this work is that Dr Brink was able to take teeth with these steak knife-like serrations and find a way to make cuts to obtain sections along the cutting edge of these teeth,” said co-author Prof Robert Reisz, also from the University of Toronto Mississauga.

“If you don’t cut them right, you don’t get the information. This brought about a developmental explanation for the tooth formation; the serrations are even more spectacular and permanent.”

The paleontologists used a scanning electron microscope and a synchrotron to do a thorough examination and analysis of tooth slices from eight carnivorous theropods, including Tyrannosaurus rex, Allosaurus, Coelophysis and Gorgosaurus.

“We present the first model for the development of ziphodont teeth in theropods through histological, SEM, and SR-FTIR analyses, revealing that structures previously hypothesized to prevent tooth breakage instead first evolved to shape and maintain the characteristic denticles through the life of the tooth,” they wrote in the paper.

“We show that this novel complex of dental morphology and tissues characterizes Theropoda, with the exception of species with modified feeding behaviors, suggesting that these characters are important for facilitating the hypercarnivorous diet of most theropods.”

“This adaptation may have played an important role in the initial radiation and subsequent success of theropods as terrestrial apex predators.”

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K.S. Brink et al. 2015. Developmental and evolutionary novelty in the serrated teeth of theropod dinosaurs. Scientific Reports 5, article number: 12338; doi: 10.1038/srep12338