Diagram showing the position of the sclerotic ring within a bird eye
A skull of a Uroplatus (leaf-tailed gecko), showing large sclerotic rings
The sclerotic ring of Ophthalmosaurus ("eye lizard") was one of the largest in the animal kingdom[1]

Sclerotic rings are rings of bone found in the eyes of many animals in several groups of vertebrates, except for extant mammals and crocodilians.[2] They can be made up of single bones or multiple segments[3] and take their name from the sclera. They are believed to have a role in supporting the eye, especially in animals whose eyes are not spherical, or which live underwater.[2] Fossil sclerotic rings are known for a variety of extinct animals, including ichthyosaurs, pterosaurs, and dinosaurs,[4] but are often not preserved.


  1. ^ Milner, Angela. "Ophthalmosaurus icenicus: Why did it have such large eyes?". Natural History Museum, London. Retrieved 15 October 2013.
  2. ^ a b Motani, Ryosuke (15 November 2001). "Eyes of Ichthyosaurs". UC Museum of Paleontology. Retrieved 15 October 2013.[dead link]
  3. ^ "Palaeos Vertebrates: Glossary S". Retrieved 2007-07-06.
  4. ^ Pigdon, Dann. "Re: Sclerotic ring in eyes". Retrieved 2007-07-06.