Somniosus is a genus of deepwater dogfish sharks in the family Somniosidae, distributed widely across the world’s oceans.
These are slow-moving, cold-water predators that inhabit the deep sea, often at depths where light does not penetrate. Several species within the genus are believed to reach lengths up to seven metres, placing them among the largest sharks in existence. The most studied member is the Greenland shark (Somniosus microcephalus), which inhabits the North Atlantic and Arctic Oceans and is notable for its extreme longevity—individuals may live for centuries, making it one of the longest-lived vertebrates known to science. Somniosus sharks possess slow metabolisms adapted to the frigid, nutrient-poor waters they occupy, and their biology remains poorly understood due to the inaccessibility of their deep-sea habitats. The genus represents an important lineage for understanding shark evolution, deep-sea ecology and the physiological adaptations required for life in extreme marine environments.
