Dromaeosaur limb mechanics
Dromaeosaur limb mechanics and the functional morphology of pedal digit II. This work has been part-funded by the BBC. Co-workers on this project include: The Natural History Museum (London), Pennicott & Payne Ltd. (London), The Peabody Museum (Yale University, New Haven, USA), Schools of Materials (University of Manchester), School of Biological Sciences (University of Manchester), Manchester Computing Centre (University of Manchester) and The Manchester Museum (University of Manchester).
The strongly recurved, hypertrophied and hyperextensible ungual claw on pedal digit II of Dromaeosaurine dinosaurs are commonly interpreted as weapons adapted to perform a disembowelling function. The effectiveness of the claw to perform a disembowelling function has been challenged by recent experiments using a hydraulic dromaeosaur hind limb (Manning et al 2006).
The robotic limb built to test the disembowelling hypothesis was designed and constructed by Pennicott Payne Models and Special Effects (London) in connection with a BBC television production (‘The Truth About Killer Dinosaurs’). The dimensions for the hydraulic limb were constrained by using the limb dimensions, articulations and functional morphology of the dromaeosaurs Velociraptor mongoliensis and Deinonychus antirrhopus.
The limb consists of an hydraulic arm, braced by steel control rods, with the segments articulated via simple pinned joints whose degree of movement could be accurately controlled and powered by hydraulic rams: the hyperextensible movement of the ungual was produced by a control cable linked to a smaller hydraulic ram.
The experiments demonstrated that Dromaeosaurine claw geometry caused the structure to rotate as it was pushed into prey, resulting in a maximum depth of trauma equal to the radius of the inside arch of the claw. The recurved claws of dromaeosaur dinosaurs were able to create an instant, live, climbing wall from the flanks of prey, allowing the serrated recurved teeth to inflict killing bites. Whilst the claw attachment would have been painful to prey, it was unlikely to have been life-threatening. An understanding of the functional morphology of recurved claws provides new insight into the ecology of dromaeosaurs and assists in the interpretation of rare dinosaur predator-prey associations.