Nevertheless, this diminutive shark is not regarded as dangerous to humans. Though rarely encountered because of its oceanic habitat, a handful of documented attacks on humans were apparently caused by cookiecutter sharks. This species has been known to travel in schools. When a would-be predator approaches the lure, the shark attaches itself using its suctorial lips and specialized pharynx and neatly excises a chunk of flesh using its bandsaw-like set of lower teeth. Its dark collar seems to mimic the silhouette of a small fish, while the rest of its body blends into the downwelling light via its ventral photophores. Cookiecutter sharks have adaptations for hovering in the water column and likely rely on stealth and subterfuge to capture more active prey. It also consumes whole smaller prey such as squid. Marks made by cookiecutter sharks have been found on a wide variety of marine mammals and fishes, as well as on submarines, undersea cables, and even human bodies. The name "cookiecutter shark" refers to its feeding habit of gouging round plugs, as if cut out with a cookie cutter, out of larger animals. It is dark brown, with light-emitting photophores covering its underside except for a dark "collar" around its throat and gill slits. Reaching only 42–56 cm (16.5–22 in) in length, the cookiecutter shark has a long, cylindrical body with a short, blunt snout, large eyes, two tiny spineless dorsal fins, and a large caudal fin. It migrates vertically up to 3 km (1.9 mi) every day, approaching the surface at dusk and descending with the dawn. This shark occurs in warm, oceanic waters worldwide, particularly near islands, and has been recorded as deep as 3.7 km (2.3 mi).
The cookiecutter shark ( Isistius brasiliensis), also called the cigar shark, is a species of small squaliform shark in the family Dalatiidae. Scymnus brasiliensis Quoy & Gaimard, 1824
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