Sixgill

Part of speech: noun

Definitions

1. A type of shark characterized by having six gill slits instead of the usual five, known for its deepwater habitat and primitive features
2. Referring to a distinctive species of shark possessing six openings for respiration on each side, typically inhabiting deeper ocean zones and exhibiting ancient anatomical traits
3. Denoting a shark genus notable for its six gill openings, often found in deep-sea environments and considered a living fossil due to its unchanged evolutionary form

Etymology: Sixgill is one of the few English compounds where the name describes the animal's anatomy almost literally: the shark has six gill slits on each side of its head, where most sharks have five. The word is simply "six" joined to "gill," with no older coinage or borrowed root behind it, so the interesting part is the anatomy it points to rather than any change in meaning. That extra gill slit is more than a curiosity. Sixgill sharks belong to a group that retains several features of very early sharks, and the sixth slit is one of the traits that set them apart from the more familiar species most people picture. The name therefore works as a compact description of a biological feature that scientists use to recognize the lineage.

Synonyms: sixgill shark