Hexanchidae
The Hexanchidae, commonly known as cow sharks or sixgill sharks, are a family of sharks belonging to the order Hexanchiformes. They are characterized by possessing six gill slits, a trait that sets them apart from most other sharks, which have five. These ancient sharks have a long evolutionary history, dating back to the late Cretaceous period. Today, they occupy various marine habitats around the world, from coastal waters to the deep sea.
Common Names
Hexanchidae are commonly referred to as cow sharks or sixgill sharks. The name "cow shark" is likely derived from their large size and slow movements. Some species, such as the bluntnose sixgill shark, may also be referred to by specific names, such as "bluntnose" or "sharpnose."
Characteristics
Hexanchidae exhibit a number of distinct characteristics, including:
- Six gill slits: This trait is unique to this family, giving them their common name.
- Large size: Many species can reach impressive lengths, with some reaching over 6 meters (20 feet).
- Slender body: Their bodies are generally elongated and somewhat flattened, giving them a streamlined shape.
- Primitive features: Hexanchidae retain a number of primitive shark features, such as a lack of an anal fin and a single dorsal fin positioned far back on the body.
- Powerful jaws: Their mouths are equipped with numerous rows of sharp, needle-like teeth, making them formidable predators.
Environment
Hexanchidae are found in a variety of marine habitats around the world, inhabiting both shallow and deep waters. Some species, such as the common sixgill shark, are known to frequent coastal waters, while others, such as the bluntnose sixgill shark, prefer the depths of the ocean.
References
For further information on Hexanchidae, consult the following sources: