FRILLNECK LIZARD MORPHOLOGY - COMPARISONS BETWEEN SEXES AND SITES

Large samples of frillneck lizards, Chlamydosaurus kingii, were measur ed from two sites approximately 150 km apart in the Northern Territory of Australia. Frill size increases linearly with SVL up to a SVL of 1 03 mm. At larger SVLs frill size continues to increase linearly, but w ith a greater slope. This inflection point corresponds to the SVL at w hich the gap between the two halves of the frill closes. The relations hip between neck length and SVLZ is a simple line without an inflectio n point. Jaw length and head width show an allometric pattern that is similar to frill length, but the inflection point corresponds to a SVL of approximately 204 mm. The significance of this change in slope is unclear because this SVL does not correspond to any known ecological o r morphological factors. Compared to females, male lizards have signif icantly larger frills, longer jaws, and wider heads for a given SVL. M ales also have a longer frill for a given head width. Morphological di fferences exist between the two sites: at one site the frill length, j aw length, and dry season masses of large males are greater for a give n SVL than those of large males at the other site, but at the second s ite the lizards of both sexes tend to have wider heads. The difference s between the sexes with respect to frill and head sizes are consisten t with the use of these structures for intraspecific displays, but the significance of the differences between the two sites is not known.