Bighead Spurdog

The bighead spurdog is a robustly built, spindle-shaped shark with a hump behind the head. The head is notably broad, and the snout is short and triangular with a blunt tip. The nostrils are preceded by a forked flap of skin. The medium-sized eyes are oval in shape and have a notch in the outside corner; behind them are small, crescent-shaped spiracles. The mouth is nearly straight and bears long furrows at the corners. There are 26–27 upper and 22–24 lower tooth rows. Each tooth has a single angled, knife-like cusp. There are five pairs of gill slits, with the first four pairs small and the fifth pair longer. The two dorsal fins bear long spines and have narrowly rounded apexes, concave posterior margins, and short free rear tips. The first dorsal fin originates above the pectoral fin insertions; the second is smaller than the first and originates behind the pelvic fins. The pectoral fins are medium-sized with rounded tips, the pelvic fins are small, and there is no anal fin. There are lateral keels on the caudal peduncle. The caudal fin is asymmetrical, with a long upper lobe and a well-developed lower lobe; the trailing margins of both lobes are convex. The skin is covered by tiny, non-overlapping dermal denticles. Unlike other Squalus species, adults have a mix of one-cusped and three-cusped denticles. …

The bighead spurdog has only been recorded from the waters south of New Caledonia, and from seamounts on the Norfolk Ridge in the northern Tasman Sea. It has been caught between the depths of 448–800 m (1,470–2,625 ft).

Virtually nothing is known about the natural history of the bighead spurdog. Male appear to mature sexually at under 66 cm (26 in) long.