Determining the Natural Head Posture for Extant Animal Species Using Line-of-Sight From the Eyesocket and Optical Foramen

Abstract

Understanding natural head posture in animals is improtant in interpreting their biomechanics and behavior. For extinct animals, natural posture cannot be directly determined from the fossil record. There have been few prior studies of animal line of sight and head posture. Most line of sight studies have focused on the breadth of binocular vision versus panoramic vision in relation to behavior (predator type or grazer, for instance) or the animals typical environment (open or cluttered) [1]. For head posture some have studied changes in cognition or the environment or related aspects like the eyeball orientation as head posture changes [2]. Still others have focused on the areas of the brain that control 3D head position [3]. However, none of these studies address a method to determine the natural head posture or angle. While there currently is no definitive way to determine natural head angle in extinct animals, it seems reasonable to assume that the natural head posture would place the line of sight in the horizontal plane for most species. Therefore, we hypothesized that the opening for the optical (the optical foremen) and the eye socket structure itself can be used to accurately determine the natural head posture for a large portion of extant and extinct animal species. Specifically, if the skull is oriented such that the plane of sight (the plane common to both lines of sight) is horizontal, then the skull will be in the natural posture. If this hypothesis is shown to be valid, it will provide naturalists a reliable tool to determine the natural head posture (head angle) of extinct animals. The objective of this study was to test the above hypothesis on animals in the Felidae (cats).