Southern sleeper shark

It was formerly sometimes viewed as conspecific with either the Greenland shark (Somniosus microcephalus), or the Pacific sleeper shark (Somniosus pacificus). ==Distribution==

A deepwater species, the southern sleeper shark is known to frequent waters around 400 m (1312 feet) to as deep as 1100 m (3608 feet). In 2025, a shark believed to be a southern sleeper was sighted at 490 meters deep in the South Shetland Trough by a research team's underwater camera, among the first ever confirmed sightings of a shark in the Southern Ocean. ==Description==

The southern sleeper shark's body length measures up to . This species differs from the Greenland shark (S. microcephalus) with the presence of additional rows of teeth in its lower jaw, a shorter interdorsal region, a more posterior first dorsal fin, and fewer precaudal vertebrae. Compared to both the Greenland and the Pacific sleeper shark (S. pacificus), the southern sleeper has lower dorsal fins, which the other two do not. ==Diet==

The southern sleeper shark feeds primarily on cephalopods, especially squid — including the giant and colossal squids — and numerous fishes. Documented stomach contents of individual sleeper sharks have also, albeit infrequently, contained the remains of marine mammals or seabirds, possibly as a result of scavenging on sunken carcasses or whale falls. Based on its generally sluggish nature and the comparative speed of its prey, it is thought to be an ambush predator. A long female, caught off the coast of Chile, had a whole southern right whale dolphin in its stomach. The dogfish is sometimes taken as accidental bycatch in the orange roughy and Patagonian toothfish fisheries; whether or not this poses a threat to the species is currently unknown. == Conservation status ==

In June 2018 the New Zealand Department of Conservation classified the southern sleeper shark as "Not Threatened" with the qualifiers "Data Poor" and "Uncertain whether Secure Overseas" under the New Zealand Threat Classification System. The IUCN also does not regard it as threatened, noting a widespread distribution and no indication of a declining population, but believes it is not naturally abundant and that much more data and understanding of its population, interactions and biology is needed. ==References==