The smallest species of Mustelus, maximum size 70 cm TL. Tip of clasper well beyond posterior margin of pelvic in a male of 360 mm TL. Interdorsal ridge distinct. Eye small, about 1/3 of preoral length, with a well developed suborbital fold. Spiracle present. Labial folds on jaws equal in length. Teeth flat, arranged in a mosaic pattern on jaws. Dermal denticles ending posteriorly in 3 points.
Distribution:
North Venezuela to Santos, Brazil.
Remarks:
Distinguishable by its small eye (half of preoral length in M. canis and M. norrisi) and dermal denticles ending posteriorly in 3 points (single in M. canis and M. norrisi). A female, 523 mm TL, contains 4 embryos (207〜215 mm TL). All the corners of their fins broadly rounded and lower caudal lobe not defined. The fin shape varies greatly in shape accompanied with growth. (Uyeno and Sasaki)