. Advances in herpetology and evolutionary biology : essays in honor of Ernest E. Williams. Williams, Ernest E. (Ernest Edward); Herpetology; Evolution. .tMiik^S^i^A ?^^'%§«* -:?*":?? fy^-\^.. Figure 1. Close-up photographs of the heads of three different scincid lizards to show the three main struc- tural stages in the evolution of the spectacle in lizards and snakes. Bottom: lower eyelid moveable (shown here raised) and scaly {Sphenomorphus tympanum); middle: lower eyelid moveable (shown here raised) but with a clear "window" (Carlia amax), and top: the large clear spectacle,
. Advances in herpetology and evolutionary biology : essays in honor of Ernest E. Williams. Williams, Ernest E. (Ernest Edward); Herpetology; Evolution. .tMiik^S^i^A ?^^'%§«* -:?*":?? fy^-\^.. Figure 1. Close-up photographs of the heads of three different scincid lizards to show the three main struc- tural stages in the evolution of the spectacle in lizards and snakes. Bottom: lower eyelid moveable (shown here raised) and scaly {Sphenomorphus tympanum); middle: lower eyelid moveable (shown here raised) but with a clear "window" (Carlia amax), and top: the large clear spectacle, permanently covering the eye {Cryp- toblepharus plagiocephalus). lids (as opposed to scaly eyelids)—and also with some pigment in the eyelid— are suspected of having crepuscular, cave-dwelling habits and are inferred to protect their presumably light sensitive eyes by raising their eyelids in daylight (Williams and Hecht, 1955). 4) Both the windowed eyelid and the spectacle re- duce evaporative water loss from the eye (Arnold, 1973) on the evidence of a) an experimental observation that corneal transpiration may account for over 20% of total transpirational loss in a small lizard at normal activity temperatures (Reich- ling, 1957; also see Mautz, 1980) and b) anecdotal but informed observation that both eyelid types are widespread in small, sun-dwelling lizards (Arnold, 1973). The purpose of this paper is fourfold. First, to test a prediction of the evapora- tive water loss hypothesis using the three squamate families in which the spectacle occurs in lineages of low taxonomic rank and in which, therefore, its original adap- tive associations may be especially clear. Second, to show that the evaporative water loss hypothesis either contradicts, or explains more parsimoniously, the ob- servations advanced in support of the other hypotheses. Third, to suggest that the evaporative water loss hypothesis has heuristic value in thinking about the evolution of those groups in whi
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Keywords: ., bookauthorharvarduniver, bookcentury1900, booksubjectherpetology
