大きな眼と1尖頭の鱗を備えることで本種と類似するM. norrisiでは,腹鰭起点は胸鰭,臀鰭両起点の中央にあり,少なくともBigelow and Schroeder(1948)によって調査された全長643mm以上の個体では,尾鰭下葉が強く後方に突出する。 (上野・佐々木)
Distinctive characters:
The moderate sized species of Mustelus, maximum size 150 cm TL. Tip of clasper not reaching to posterior margin of pelvic in a male of 621 mm TL. Interdorsal ridge distinct. Pelvic origin considerably closer to anal origin than to pectoral origin. Eye large, about half of preoral length, with a well developed suborbital fold. Spiracle present. Labial fold on upper jaw longer than that on lower jaw. Teeth flat, arranged in a mosaic pattern on jaws. Dermal denticles ending posteriorly in a single point.
Distribution:
New Brunswick, Canada to Uruguay.
Remarks:
The present species resembles M. norrisi in having large eye and dermal denticles ending in a single point. M. norrisi has insertion of pelvic about equidistant between pectoral and anal origins, and pointed lower caudal lobe directed backward, at least in 643 mm and larger specimens examined by Bigelow and Schroeder (1948). (Uyeno and Sasaki)