Research

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Feeding adaptations in the skulls of carnivorous archosaurs

     Finite element analysis (FEA) of archosaur skulls enables us to discern patterns and relative magnitudes of stress and strain under hypothesized feeding behaviors. rex  Lab's current FEA research centers on feeding adaptations of carnivorous archosaurs, including raptorial birds and large theropod dinosaurs. Theropods have S-shaped necks with the head carried high, which in modern birds is good for striking down and forwards, and pulling up and back (Snively et. al. 2013). However, Tyrannosaurus rex could also strike and dismember prey with rapid sideways movements of the head (Snively and Russell 2007, Witmer and Ridgely 2009).  

Image by Ryan Ridgely, Ohio University. Ryan animated the full reconstruction (front) to follow motions of the dynamics model (back).

Image by Ryan Ridgely, Ohio University. Ryan animated the full reconstruction (front) to follow motions of the dynamics model (back).

Multibody dynamics of feeding movement

     In collaboration with John Cotton, Ryan Ridgely, and Larry Witmer at Ohio University, I am applying multibody dynamics to model and visualize head movements in divergent yet successful Mesozoic theropods (Snively et al. 2013).  At UW-LAX, we are validating our methods with extant raptors and crocodilians. Through biomechanical modeling we will test two main hypotheses: The exquisitley preserved abelisaur Majugasaurus crenatissimus, with its bulldog head and derived neck, struck best to the side like a crocodilian or tyrannosaur. In contrast, with its narrow base for muscle attachment yet the largest head among land carnivores, the enormous Giganotosaurus carolinii best struck down and forward like a predatory bird.

 

 Evolution and ontogeny of predation

      Biomechanical studies of feeding tie in with larger questions of evolution, ecology, and ontogeny of predation. At the University of Alberta with Philip Currie and Eva Koppelhus, I began large-scale integration of biomechanics, growth, and trophic behavior in theropods and ancient predatory fish. Colleagues Lara SurringMichael BurnsRobin Sissons, and I are correlating feeding and locomotor adaptations in tyrannosaurids with their predatory hegemony in late Cretaceous Laurasia (Holtz 2009). With Meagan Gilbert (University of Saskatchewan), Robin Sissons, and Lauren Schultz (UW-LAX), I am testing the mechanical and bone material response of ostrich limb bones to forces of locomotion.

 

Columbia, a bald eagle (Haliaeetus leucocephalus), takes a drink at the National Eagle Center (Wabashaw, Minnesota).

Columbia, a bald eagle (Haliaeetus leucocephalus), takes a drink at the National Eagle Center (Wabashaw, Minnesota).

 Quantifying how birds use their necks

      Raptorial birds use their long, S-shaped necks to strike at prey, tear flesh, and (more rarely) to dip the head to drink. We are using high-speed video and software from sports medicine to quantify the path and speed of these motions. These films document how different raptors feed, and will test the accuracy of biomechanical computer models of their heads, necks, and feeding motions.

All-American sprinter Shannon Klein explains greater stress/load in her tibia compared with her colleague, wrestler Zach Tooley. Taryn Ashley and Hannah Lawinger tested hypotheses by modelling their own foot and leg bones.

All-American sprinter Shannon Klein explains greater stress/load in her tibia compared with her colleague, wrestler Zach Tooley. Taryn Ashley and Hannah Lawinger tested hypotheses by modelling their own foot and leg bones.

Subject-specific stress analyses in female athletes

In collaboration with Drs. Tom Kernozek and Nagmeh Gheidi, we are applying ground, muscle, and joint forces from running in athletes to finite element models of the subjects' own bones. We hope to discover how gait modification may minimize stress fractures (including shin splints) in female athletes. Results so far suggest that high-performing female sprinters have slightly lower safety factors than males. Pinpointing high stress where our participants have experienced stress fractures is an encouraging validation of our methods.