Research
Volumetric models of tyrannosaurs: adult Tyrannosaurus, juvenile Tarbosaurus, and adult Gorgosaurus.
Evolution of mass properties and relative locomotor performance of fossil animals
Animals’ muscles overcome mass and rotational inertia to accelerate their bodies in a straight line or to change direction. We estimate mass properties with rigorously variable reconstructions of anatomy. Combined with similarly range-bound estimates of musculoskeletal torques, we discovered that tyrannosaurs were more agile than other carnivorous dinosaurs across their entire parallel size ranges (Snively et al. 2019). Cutting-edge phylogenetic comparative analyses by Dr. Haley O’Brien (University of Arizona) anchor inferences of predatory function across spans of evolution and growth.
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 dismember prey with rapid sideways movements of the head (Snively and Russell 2007, Witmer and Ridgely 2009).
Adult bison (background) and juvenile dinosaur bone, imaged and reconstructed with synchrotron x-ray scanning.
3D histology of bone growth in mammals and dinosaurs
X-rays at the Canadian Light Source synchrotron (Saskatoon, Saskatchewan) are revealing the bone-building blood vessel systems in dinosaurs and mammals, enabling us to compare their histology (tissue structure) in 3D. Small juvenile dinosaurs had dense blood vessel canals like baby birds, a hallmark of explosively fast early growth. Phase-contrast imaging gives us better object resolution than traditional x-ray computed tomography (CT).
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 stresses in female athletes
Runners often experience repetitive stress injuries in their shins and feet. In collaboration with Dr. Tom Kernozek (UW-La Crosse), 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.
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
We are applying multibody dynamics to model and visualize head movements in divergent yet successful Mesozoic theropods (Snively et al. 2013), and are validating our methods with extant crocodilians and birds. Collaborations with Lawrence Witmer, Ryan Ridgely and John Cotton (Ohio University) reveal head and neck accelerations in archosaurs, and enable us to infer feeding style.