This flattish toad was about 3" long, colored in splotchy browns that matched the leaf litter really well. The "crest" in its name refers to the wavy crest extending out from each side of its head from eye to shoulder (see photo #2). The crest breaks up into tiny knobs, continuing toward the rear. This one had a sharp white stripe down its back, and a dark pointy nose.
It was found in one of the alcoves between the buttress roots of a giant Ceiba tree in the leaf litter. The Peruvian guide is holding it in photo #2.
The name South American Common Toad seems all wrong to me, as it isn't common and doesn't look like a typical "common toad."