Kent Stevens, University of Oregon
Thursday, November 1, 2012
ABSTRACT: It is often presumed that sauropod dinosaurs walked like elephants, despite the fact that they may have shared little in common with modern elephants other than their both being quadrupedal, herbivorous, and large. Likewise, sauropods are imagined to have used their long necks for high browsing, as giraffes often do, and to have held their heads high, as swans often do. Analogical reasoning based on superficial similarities with living animals underlies much of how we imagine dinosaurs, and sometimes leads to wild conjectures regarding sauropods because of their muchness. After a brief review of what we know (and don’t know) about how sauropods looked, moved, and behaved, we will consider the role of computational modelling in trying to under-stand these extinct giants, in particular, how they walked. Fossil trackways provide dramatic evidence for sauropod locomotion, when their giant footprints were imprinted in a compliant surface that subsequently turned to stone. Trackway interpretation usually begins with the taxo-nomic classification of the trackmaker, based on the size, spacing, and morphology of the individual footprints. But attempts to identify which taxon of sauropod created a given track often relies on assumptions about how the creatures walked, which introduces circularity when one subsequently attempts to understand their pattern of locomotion, which requires having first identified the track maker. Trackway interpretation is thus more poorly constrained than often recognized, and would require additional, independent lines of evidence, such as kinematics and dynamics. A few computational studies have introduced such notions through articulated models that simulate the sauropod’s pattern of locomotion. To be sufficiently concrete as to permit animation, these studies must incorporate a large number of rather specific presumptions about the track maker and its walking behaviour. Instead, we have adopted an incremental strategy for the incorporation of such constraints which seeks to maximize what can be concluded from the few-est and most conservative assumptions while attempting to replicate fossil trackways and observe-able behaviours associated with locomotion.
BIO: Professor Stevens received an undergraduate degree in engineering (1969) and a masters in computer science (1971) at UCLA, with computer graphics thesis research on the Fisheye Transform, under Professor Leonard Kleinrock. Since the early 70s, computer graphics has remained a central tool throughout his varied research career. During his Ph.D. studies at the MIT Artificial Intelligence Laboratory under the supervision of Professor David Marr, he used Lisp Machines to generate novel visual stimuli for psychophysical experiments and to visualize the results of perceptual algorithms. After Stevens received his Ph.D. in 1979, he was a Research Scientist position at the AI Laboratory until he joined the faculty of the University of Oregon in 1982 where he continued to use computer graphics primarily to create 3D visual stimuli to explore the strategies underlying monocular and binocular depth perception. His interest in human vision led to a US Patent for a graphical means to measure and correct metamorphopsia (a visual disorder often associated with macular degeneration). He has been an industrial consultant regarding virtual reality, machine vision, and visual fight simulation. Since 1994, Stevens has also applied 3D computer graphics and digital animation techniques towards to create an interdisciplinary link with vertebrate palaeontology. Through the creation and animation of articulated digital models of dinosaur skeletons, Stevens has explored a variety of biomechanical questions that assist in the visualization of dinosaurs and the reconstruction of their appearance, movements, and behaviours.
Professor Stevens has consulted and appeared in BBC, National Geographic, NHK, Discovery Channel, and other video productions, creates digital media and interactive displays that are on exhibit in many museums internationally including New York, Pittsburgh, Los Angeles, and Tokyo, and presents his research in international palaeontological meetings. Co-Sponsored by University of Colorado Museum of Natural History, Sigma Xi, and the Department of Geological Sciences.
Hosted by Liz Bradley.
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