Heterodontiformes
The Heterodontiformes are an order of cartilaginous fish that encompasses a single extant family, Heterodontidae, known as bullhead sharks. These sharks are distinguished by their unique features, including their robust bodies, blunt snouts, and distinctive dentition. Heterodontiformes represent a distinct lineage within the chondrichthyan evolutionary tree, exhibiting an intriguing combination of ancestral and derived traits.
Common Names
Common names for members of this order include bullhead sharks, bullhead dogfish, and Port Jackson sharks. These names reflect the sharks' appearance, which often includes a blunt, bulldog-like head.
Characteristics
Heterodontiformes possess a number of defining characteristics that distinguish them from other shark orders. Some of the most notable features include:
- Robust Body: Bullhead sharks have a stocky, robust body shape with a distinctive rounded head.
- Blunt Snout: Their snout is short and blunt, contributing to their bulldog-like appearance.
- Dorsal Spines: They have two prominent dorsal fins, each supported by a sharp, venomous spine.
- Heterodont Dentition: The most distinctive feature of bullhead sharks is their heterodont dentition. Their teeth are differentiated, with sharp, pointed teeth in the front for grasping prey and crushing teeth in the back for grinding.
- Nocturnal Habits: Bullhead sharks are primarily nocturnal, hiding in crevices and caves during the day and emerging at night to hunt.
Environment
Heterodontiformes are primarily found in coastal waters, particularly in temperate and subtropical regions around the world. They prefer rocky reefs, seagrass beds, and other shallow-water habitats. Bullhead sharks are known for their ability to tolerate a wide range of salinity, allowing them to inhabit both marine and brackish environments.
References
For further information on Heterodontiformes, consult these reliable sources: