Dinosaur Teeth Provide Information on the Diet of Theropods

Palaeontologists have speculated on the preferred prey of Theropod dinosaurs for decades.  These mainly meat-eating dinosaurs did not chew their food but bit into their victims and tore off chunks of flesh, a feeding technique named “puncture and pull”.  In newly published research, scientists have looked at the serrations on the sides of Theropod teeth and assessed their role in feeding.  An analysis of microscopic scratches and wear patterns on the teeth of several different types of Canadian and Spanish carnivorous dinosaur has revealed that the troodontid dinosaurs with their large, broad and hooked, serrations (denticles) may have specialised in hunting smaller, softer prey as their teeth might have been damaged if they had bitten into a struggling, large animal.

Study of Dinosaur Tooth Serrations Suggest Differences in Preferred Prey

Various Theropods involved in the tooth study.

The serrated teeth of Theropod dinosaurs provides evidence of preferred prey.  The teeth in the picture have been scaled to the same crown height for comparative purposes.

Picture Credit: Current Biology

The Ziphodont Teeth of Theropods

The teeth of meat-eating dinosaurs tend to be curved, with sharp, serrated edges (ziphodont), the shape and size of the tooth serrations (the denticles) varies considerably between different species.  Tyrannosaurids such as the North American Gorgosaurus and dromaeosaurids such as Dromaeosaurus both have rounded, almost rectangular denticles, despite these animals being very different sizes, with the Gorgosaurus having much larger teeth.  In contrast, the dromaeosaurid Saurornitholestes has more pointed denticles that, over time can become worn and then they resemble the serrations found on the tooth of Dromaeosaurus.  Troodontids, such as Troodon have unique hooked denticles, that are proportionally much bigger than the denticles found on similarly sized Theropods.  Troodon means “wounding tooth”, a reference to the large, distinctive serrations on its teeth.

This new study under taken by University of Alberta scientists, along with colleagues from the Universidad de Zaragoza and the Universidad de La Rioja (Spain) and the Royal Ontario Museum, examined the strength of the teeth and their serrations to see whether they provided any clues about potential prey as these dinosaurs fed using the “puncture and pull” technique.

Microscopic Scratches on Dinosaur Teeth Identified by Scanning Electron Microscopy

Scratches and microwear support the idea of a "puncture and pull" feeding technique.

Tiny scratches (highlighted in yellow) support the idea of puncture and pull feeding in Theropod dinosaurs.

Picture Credit: Current Biology

The picture (above), shows microwear patterns on three different Theropod teeth (scale bar = 100 um).  Each pair of pictures shows the same section of tooth with the microwear and scratches highlighted in yellow on the picture (right).  Two scratch orientations were present on all studied teeth, one oriented parallel to the border of the tooth, and one oriented 30°–40° to the tooth border, this supports the idea of “puncture and pull” feeding behaviour.

The photographs at the top show the denticles of Pyroraptor, a dromaeosaurid from Laño, Spain.  The middle photographs represent the tyrannosaurid Gorgosaurus from the Dinosaur Provincial Park (Alberta, Canada).  The photographs (bottom) show the denticles of Troodon (T. inequalis), also from the Dinosaur Provincial Park (Alberta, Canada).

Microwear and Finite Element Analysis

The researchers used scanning electron microscopy to map the wear and scratches on individual serrations in conjunction with a statistical method (finite element analysis), to identify stress patterns in teeth as they were involved in feeding.

Commenting on the research, one of the authors of the scientific paper, Ryan Wilkinson (University of Alberta), explained that their study supported the idea of “puncture and pull” feeding:

“We found the microwear patterns were similar in all of the teeth we examined, regardless of the size of the dinosaur, the size of the tooth or the shape of the denticles.”

It was concluded that the shape and strength of the dinosaurs’ teeth made them more or less vulnerable to breakage, forcing them to select different types of prey.  For troodontids, their tooth serrations were particularly prone to stress and therefore not suited to coping with struggling prey.  This suggests that although troodontids were of a similar size to many dromaeosaurs, they may have selected much smaller, less mobile prey, hinting at niche partitioning in those environments were dromaeosaurs and troodontids may have been coeval.

Stress Tests on Different Theropod Teeth

Stress tests on different Theropod dinosaur teeth.

Stress assessments of different Theropod teeth.

Picture Credit: Current Biology

The picture above shows plotted stress tests on three types of Theropod dinosaur teeth – Dromaeosaurus (top), the dromaeosaurid Saurornitholestes (middle) and a troodontid (bottom).  The “hotter” the colour ie. red, orange, yellow, the greater the stress on that part of the tooth during a bite.

The teeth of troodontids were identified as being particularly susceptible to breakage when biting into struggling prey.

Ryan Wilkinson added:

“The large hooked denticles of troodontids acted like a lever and caused high stress within the denticles and the tooth, which may cause the tooth to break.”

Implications for Feeding Troodontids

The researchers, which included renowned Ankylosaur expert Victoria Arbour of the Royal Ontario Museum and a former student at the University of Alberta working with Professor Phil Currie, who also contributed to the study, conclude that the microwear evidence supports the idea of “puncture and pull” feeding in Theropod dinosaurs and that troodontids may have favoured smaller prey than dromaeosaurids, as their teeth did not stand up so well to the stresses and strains of coping with struggling prey.

The “Puncture and Pull” Feeding Technique as Demonstrated by the Dromaeosaurid Saurornitholestes

The Theropod puncture/pull feeding technique.

Saurornitholestes demonstrates the puncture/pull feeding technique of Theropod dinosaurs.

Picture Credit: Sydney Mohr with additional annotation by Everything Dinosaur

Dromaeosaurus and Saurornitholestes were well-adapted for handling struggling prey, whilst troodontid teeth indicate that these dinosaurs may have had a different diet.

Troodon May Have Tackled Small Prey

Beasts of the Mesozoic Troodon.

The Beasts of the Mesozoic Mountains accessory pack, features Troodon.  New research suggests that Troodon may have fed on different prey when compared to dromaeosaurids.

Picture Credit: Everything Dinosaur

The scientific paper: “Puncture-and-Pull Biomechanics in the Teeth of Predatory Coelurosaurian Dinosaurs” by Angelica Torices, Ryan Wilkinson, Victoria M. Arbour, Jose Ignacio Ruiz-Omeñaca and Philip J. Currie published in “Current Biology”.

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