. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. I't. if*. Figure'16. The setae in A. auratus. a) Illustrates setae on the fourth lamellae (scale 12). b) Illustrates setae on the claw base (scale 1). c) Shows setae on scale 21 just distal to the metatarsal-phalangeal joint. is present on the subdigital scale, while the lateral digital scale is multicarinate. Distally (, scale 3) where the subdi- gital scale wraps 180° around the pha- lanx, all three pairs of lateral keels (plus an additional median-lateral keel) are present on the subdigital scale, while the lat
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. I't. if*. Figure'16. The setae in A. auratus. a) Illustrates setae on the fourth lamellae (scale 12). b) Illustrates setae on the claw base (scale 1). c) Shows setae on scale 21 just distal to the metatarsal-phalangeal joint. is present on the subdigital scale, while the lateral digital scale is multicarinate. Distally (, scale 3) where the subdi- gital scale wraps 180° around the pha- lanx, all three pairs of lateral keels (plus an additional median-lateral keel) are present on the subdigital scale, while the lateral digital scale is small and unicari- nate. The fine structure of the subdigital keels and bosses is comparable to that in annectens, adult onca, and chrysolepis. But there is a major difference in keel placement. In those species, a median keel is present and often the dominant scale feature. In auratus the homologous central region of the scale is covered with setae (Fig. 17). The dimensions, density, and orientation of these setae are com- parable to those of the lamellar setae (with the possible exception of stalk height, which may be reduced). The se- tae grade into prongs and tall spikes ad- jacent to the lateral keel. Over the lateral region of the scale, including the zones between the keels (, the lateral and far lateral keels), the scale surface is cov- ered with spikes and prongs. While the combination of features, par- ticularly the grade from setae to spines to keel, is very similar to that on scale 9 in annectens (compare Figs. 5 and 17), there are some interesting differences. 1) In annectens the grade from setae to spines occurs on the medial side of nu- merous bosses scattered along the distal margin of the scale. The field of setae is much less coherent than in auratus. 2) The spikes and prongs are numerically dominant on the transitional scales in an- nectens, while in auratus the setae are much more common. Figure 17. The morphological grade from spi
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