Distinguished by it's seven gills (most sharks have 5), this shark has a large, thick body, with a broad head and blunt snout. The top jaw has jagged, cusped teeth and the bottom jaw has comb-shaped teeth. Its single dorsal fin is set far back along the spine towards the caudal fin, and is behind the pelvic fins. In this shark the upper caudal fin is much longer than the lower, and is slightly notched near the tip. Like many sharks, this sevengill is counter-shaded. Its dorsal surface is silver-gray to brown in order to blend with the dark water and substrate when viewed from above. In counter to this, its ventral surface is very pale, blending with the sunlit water when viewed from below. The body and fins are covered in a scattering of small black & white spots. In juveniles, their fins often have white margins.

Common in the murky inlets's of Otago Harbour in the summer months. Also spotted up fresh water rivers on the East Coast of Stewart Island in Summer. Large, old individuals tend to live in deep offshore environments as far down as 136 m. However, most individuals live in either the deep channels of bays, or in the shallower waters of continental shelves and estuaries. These sharks are mainly benthic in nature, cruising along the sea floor and making an occasional foray to the surface.

An opportunistic predator, the broadnose sevengill preys on a great variety of animals. It has been found to feed on sharks, rays, chimaeras, cetaceans, pinnipeds, bony fishes, and carrion. These sharks occasionally hunt in packs to take down larger prey, using tactics such as stealth to succeed.

This sevengill, like all other members of Hexanchiformes, is ovoviviparous. After a 12 month gestation period, the female moves to a shallow bay or estuary in order to give birth to a large litter of up to 82 pups born at 40-45 centimetres. The juveniles remain in this nursery for a couple of years before venturing out. The probable predators of this species are larger sharks. Potentially dangerous, attacks on humans are unusual. Six attacks on humans by the broadnose sevengill, the latest being in 2013 in New Zealand, have been recorded since the 16th century, with no known fatalities. Lower teeth were prized cutting tools for human flesh by the early Maori.

Shark Attacks Diver in Fiordland - national | Stuff.co.nz accessed 13 July 2010 Compagno (2000). Notorynchus cepedianus. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org