Heterodontidae

The Heterodontidae is a family of cartilaginous fishes belonging to the order Heterodontiformes, commonly known as bullhead sharks. This family is one of the most primitive groups of sharks, characterized by their unique anatomical features and relatively small size. Heterodontids are found exclusively in the coastal waters of the southwestern Pacific Ocean, particularly around Australia and New Zealand.

Members of this family are easily recognizable by their broad, flattened heads, small eyes, and distinctive heterodont (different-toothed) dentition. Their front teeth are adapted for grasping prey, while the rear teeth are flattened and suited for crushing shellfish, their primary diet. Unlike most sharks, Heterodontidae possess a well-developed spiral valve in their intestines, a feature more commonly associated with benthic (bottom-dwelling) fishes.

The family includes two extant genera: *Heterodontus* and *Heterodontus* (though some classifications treat them as a single genus with multiple species). The most well-known species is the horn shark (*Heterodontus francisci*), which inhabits the waters of California and Baja California. Another notable species is the Port Jackson shark (*Heterodontus portusjacksoni*), found in southern Australia and Tasmania. These sharks typically reach lengths of 1 to 1.5 meters (3.3 to 4.9 feet) and exhibit a slow growth rate and long lifespan, with some individuals living over 50 years.

Heterodontids are generally non-aggressive toward humans and play an ecological role as both predators and prey within their marine environments. They are oviparous, meaning they lay eggs encased in protective leather-like capsules, which are often referred to as "mermaid’s purses." Conservation status varies among species, with some populations facing threats from habitat degradation, fishing, and climate change. Efforts to monitor and protect these sharks are ongoing to ensure their survival in changing oceanic conditions.