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"Typical sharks", such as requiem sharks, have tails with the upper lobe longer than the lower. The upper lobe is turned upwards at a moderate angle relative to the body, which balances cruising efficiency with turning ability. The thresher sharks have an extreme example of this tail in which the upper lobe has evolved into a weapon for ...
The shape of the hammerhead shark's head may enhance olfaction by spacing the nostrils further apart. Sharks have keen olfactory senses, located in the short duct (which is not fused, unlike bony fish) between the anterior and posterior nasal openings, with some species able to detect as little as one part per million of blood in seawater. [61]
The simpler structure is found in jawless fish, in which the cranium is represented by a trough-like basket of cartilaginous elements only partially enclosing the brain, and associated with the capsules for the inner ears and the single nostril. [9] Cartilaginous fish, such as sharks, also have simple skulls.
The head of the frilled shark is broad and flat, with a short, rounded snout. The nostrils are vertical slits, separated by a flap of skin that forms the incurrent opening and the excurrent opening. The moderately large eyes are horizontal ellipsoids, which have no nictitating membrane, which is a protective, third-eyelid. Ligaments articulate ...
The head or skull includes the skull roof (a set of bones covering the brain, eyes and nostrils), the snout (from the eye to the forward-most point of the upper jaw), the operculum or gill cover (absent in sharks and jawless fish), and the cheek, which extends from the eye to the preopercle. The operculum and preopercle may or may not have spines.
Baleen whales have two blowholes positioned in a V-shape, while toothed whales have only one blowhole. [6] The blowhole of a sperm whale , a toothed whale, is located left of centre in the frontal area of the snout, and is actually its left nostril, while the right nostril lacks an opening to the surface and its nasal passage is otherwise well ...
The following outline is provided as an overview of and topical guide to sharks: Sharks (superorder Selachimorpha) are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 440 million years ago, before the time of the dinosaurs. [1]
The bonnethead (Sphyrna tiburo), also called a bonnet shark or shovelhead, [3] is a small member of the hammerhead shark genus Sphyrna, and part of the family Sphyrnidae.It is an abundant species in the littoral zone of the North Atlantic and the Gulf of Mexico, is the only shark species known to display sexual dimorphism in the morphology of the head, and is the only shark species known to be ...