Hammerjaw
The hammerjaw, Omosudis lowii, is a small deep-sea aulopiform fish, found worldwide in tropical and temperate waters to 4,000 m depth. It is the only representative of its family, Omosudidae.
Description
The large head is dominated by a massive, truncated lower jaw and large, high-set eyes. The lower jaw has a dark, almost black distal end, "chin". The lower jaw possesses at least one pair of oversized, transparent, and dagger-like teeth; the palatines possess 1-4 pairs of slightly smaller teeth. The body itself is scaleless and laterally compressed; it is covered in iridescent, silvery-gray guanine with the dark peritoneum peeking through in places. Dark smoky gray dorsally, the body tapers strongly towards a thin caudal peduncle and deeply forked caudal fin. The caudal peduncle is a smoky black color, darker than the body and tail. All fins are spineless; both the low-slung pectoral fins and abdominal pelvic fins are fairly small.The single dorsal fin and anal fin are roughly equal in size; the anal fin's origin lies immediately posterior to the dorsal. The lateral line is uninterrupted and the gill rakers number 20-25. Like other members of their order, hammerjaws also possess a small adipose fin. The largest recorded hammerjaw measured 23 cm standard length.