Meeting Abstract
P3.44 Jan. 6 Inferring Binocular Visual Field Overlap in Non-Avian Dinosaurs Based on an Extant Avian Scaling Model HALL, M.I.*; HEESY, C.P.; CARRANO, M.T.; Midwestern University; Midwestern University; Smithsonian Institution margaretihall@yahoo.com
The primary sensory mode of prey location by predatory theropod dinosaurs is the subject of continued speculation. The potential development of stereoscopically based depth perception has been cited in these arguments. This speculation has been based largely on qualitative judgments of the degree of orbital convergence (the degree to which each orbital margin faces in the same direction) and resulting visual field overlap. Other studies rely on modeling and dinosaur life reconstructions. No study conducted to date has adequately quantified orbit orientation in non-avian dinosaurs using data taken directly from specimens. Also, there is confusion regarding the assessment and adaptive significance of binocular vision and its relationship with stereopsis. In this study we estimate the maximum fields of binocular overlap in non-avian dinosaurs using an extant avian comparative scaling model. We quantify the relationship between orbit and visual field orientation in visually directed avians. 3-D coordinate data on orbit orientation were collected on skulls of extant avians for which data on binocular visual field data are available as well as in a small sample of non-avian dinosaurs including Tyrannosaurus. In general, the relationship between binocular visual field overlap and orbit convergence in birds is negatively allometric, and maximum binocular visual field overlap is moderate even in taxa with more convergent orbits. Regression estimates of binocular overlap in non-avian dinosaurs suggest that these animals had minimal binocularity in life. Based on these results, we suggest that binocular vision as a mode of prey location in theropods has been over-emphasized, and that orbital convergence cannot be used to distinguish between potential hunting modes.
