Ichthyosaurian Eyes: Paleobiological Information Content In The Sclerotic Ring Of Caypullisaurus (Ichthyosauria, Ophthalmosauria)

In the eyes of many extant reptiles there is an osseous ring embedded within the sclera and around the cornea. This sclerotic ring was well developed and is frequently preserved in ichthyosaurs. Significant information can be drawn from it, such as eyeball diameter and relative size of the cornea. Estimation of these parameters in extinct forms is significant as they are closely related to vision capability. This paper presents insights into the growth pattern and vision capabilities of some Jurassic ichthyosaurs as inferred from the analysis of the sclerotic rings and orbit sizes. The suggested growth pattern of ichthyosaur eyes is similar to that of human eyes. Thus, the cornea did not grow as much as the rest of the eye. The relative size of the sclerotic ring and orbits can be used as a complementary criterion for estimating relative age in some ichthyosaurs. In juveniles the aperture of the sclerotic ring represents approximately 20% of the orbital area. This percentage decreases in adults.