These are heavy bodied snakes, and share the same general body structure with cottonmouths. They average around 60 cm (23.6 in) in length and have a broad, triangular shaped head with small eyes that have vertical pupils.
Coloration can vary, but most are brown or black, with darker brown or black banding, sometimes with white or cream colored accents. A. taylori is known for being more elaborately patterned, often having distinct tan colored banding, sometimes with orange or yellow accents that can almost appear gold in color. There are the following distinctive yellow and/or white lines on the head: a vertical line on the rostral and mental, a fine line on the canthus continuing above and beyond the eye to the neck, a broader line on the upper lip from the anterior nasal to the last labial. Juveniles are almost always distinctly banded, with bright green or yellow tail tips, which they use to lure prey. As they age, their pattern and coloration fade and darken.
Cantil, common cantil, Mexican moccasin, tropical moccasin, Mexican cantil. The common name, cantil, is based on the Tzeltal word kantiil, which means "yellow lips."
