. Advances in herpetology and evolutionary biology : essays in honor of Ernest E. Williams. Williams, Ernest E. (Ernest Edward); Herpetology; Evolution. Kinesis in Alligator Lizards • Frazzetta 235 Upper J a w^ point lowerjaw poinl. Figure 9. Head of Gerrhonotus showing points and axes used in Vanguard analysis. mzl-ch angle sometimes corresponds poorly with other kinetic indicators. The sequences all start at time-zero when the mouth first starts to open. Hence, the delivery phase has already begun shortly before the graphs begin. Prey Captured on the Substrate Typically the ear top point sho
. Advances in herpetology and evolutionary biology : essays in honor of Ernest E. Williams. Williams, Ernest E. (Ernest Edward); Herpetology; Evolution. Kinesis in Alligator Lizards • Frazzetta 235 Upper J a w^ point lowerjaw poinl. Figure 9. Head of Gerrhonotus showing points and axes used in Vanguard analysis. mzl-ch angle sometimes corresponds poorly with other kinetic indicators. The sequences all start at time-zero when the mouth first starts to open. Hence, the delivery phase has already begun shortly before the graphs begin. Prey Captured on the Substrate Typically the ear top point shows a rather smooth, continuous path in both x and y displacements. This is seen in Figure 10. The jaw tips, too, run a fairly continuous course up to the time when the mandibular tip is placed upon the substrate. From that time on, there is little or no vertical change in the lower jaw tip (Ijy in Figs. 10, 11A,B,C) because it slides—or nearly does—along the sub- strate toward the prey. In the cases shown in Figures 10 and IIB, the hori- zontal motion of the lowerjaw tip (Ijx) is erratic as the moment of prey capture is approached. In two other cases of capture on the substrate (Fig. 11A,C) the lower jaw tip moves in a smoother manner. During this period, the upper jaw move- ments—both horizontal and vertical (iijx and y)—are reasonably smooth in three of the four substrate captures; the exception is the sequence shown in Figure 10. Tilting of the head, shown by angular changes in the parietal top axis (pt), is different in each of the four substrate captures. In Figure 10 the head tilts sharply downward just before the mandibular tip touches the substrate, and then rotates further downward at varying rates thereafter. In Figure llA the down- ward tilt begins after the mandibles come into contact with the prey and, as before, proceeds at a discontinuous rate. How- ever, in the captures shown in Figure IIB and C, the head begins to turn up- ward from the time of mandib
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Keywords: ., bookauthorharvarduniver, bookcentury1900, booksubjectherpetology
