Meeting Abstract

P2.118A  Saturday, Jan. 5  The relationship between scleral ring morphology and activity pattern in birds and dinosaurs HALL, MI*; KAMILAR, JM; KIRK , EC; CARRANO, MT; IWANIUK, AN; Midwestern University; Midwestern University; UT Austin; Smithsonian Institution; University of Lethbridge mhallx1@midwestern.edu

Activity pattern, the time of day when an animal is awake and active, is highly associated with that animal’s ecology. Extinct bird and dinosaur activity patterns are presently poorly understood but would provide important contributions toward understanding their paleoecologies. Soft-tissue studies of eyeball measurements show that extant birds exhibit characteristic eye shapes associated with their activity pattern. Specifically, nocturnal bird eyes are optimized for visual sensitivity with a relatively large corneal diameter and diurnal bird eyes are optimized for visual acuity with a relatively large axial diameter. Orbit morphology reflects eyeball shape and activity pattern can be interpreted from measurements of the scleral ring plus the orbit. Recent studies utilizing a new statistical technique suggest that measurements of the scleral ring even without a complete orbit are sufficient to make activity pattern interpretations for fossil birds and dinosaurs. Here, we analyze scleral ring measurements of over 500 species of extant birds and lizards within a phylogenetic context, and apply the results to interpret dinosaur scleral rings. Several factors preclude reliable interpretation of activity pattern from measurements of the scleral ring, and we conclude that these measurements are not sufficient to interpret activity pattern. Instead, more measurements of the orbit are required, especially orbit depth, to infer activity pattern with any certainty.