Chapter 1, The Reptilian Spectacle - UWSpace - University of ...

Chapter 1, The Reptilian Spectacle: A Review
Many squamates possess a layer of transparent integument that overlays their eyes, shielding them
from the external environment. These “reptilian spectacles” are ubiquitous among snakes but also
found in most geckos and in several other squamate families, such as among skinks, xantusiid night
lizards, some lacertid and teiid lizards, and in many legless, burrowing reptiles such as amphisbaenids.
This review will discuss the anatomy and physiology of the spectacle as well as its diversity and
functional significance. The anatomical variation of the spectacle across families will be described
with emphasis on its unusual traits that have no analogue in unspectacled vertebrates. The optical
implications of the spectacle to vision will be discussed and will touch upon the implications of its
shape and the properties of its hard, keratinized scale, which is unique in being the only keratinized
structure in the animal kingdom to contribute to the dioptric apparatus of the eye. The diversity of
spectacle types, including windowed eyelids, will be discussed and theories on the adaptive
significance and evolution of the spectacle will be presented. Throughout, the holes in our knowledge
of this strange and fascinating structure will be emphasized and suggestions for fruitful avenues of
research will be made.
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