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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 tiger shark must be able to twist and turn in the water easily when hunting to support its varied diet, whereas the porbeagle shark, which hunts schooling fish such as mackerel and herring, has a large lower lobe to help it keep pace with its fast-swimming prey. [38]
The speartooth shark has a streamlined, rather robust body with a short, wide head. The snout is flattened, with large nostrils divided into incurrent and excurrent openings by large, triangular flaps of skin. The eyes are small and equipped with nictitating membranes (protective third eyelids). The sizable, arched mouth has very short furrows ...
Now, new research into shark DNA could potentially hold the key to cures for human diseases like cancer, but first scientists have to understand exactly what is going on in the animals' genes.In a ...
The caudal fin has a longer upper lobe without a notch in the trailing margin, and an indistinct lower lobe. The skin has a dense, uniform covering of non-overlapping dermal denticles measuring up to 0.4 cm (0.16 in) across, which are never fused together as in the bramble shark. Each denticle is thorn-like, with strong ridges running down the ...
The asymmetrical caudal fin has a well-developed lower lobe and a long, narrow upper lobe with a ventral notch near the tip. The prominent lateral line curves downward below the second dorsal fin. The skin is densely covered by small, overlapping dermal denticles; each bears five horizontal ridges leading to marginal teeth. This species is ...
The caudal fin has a small but well-defined lower lobe and a longer upper lobe with a ventral notch near the tip. The skin is often loose. This species is dark gray to bronze above and white below. Young sharks are mostly unmarked, while adults vary from plain to densely covered with irregular black spots.
The caudal fin has a well-developed lower lobe and a prominent ventral notch near the tip of the upper lobe; in young sharks the lower caudal fin lobe is much less distinct. [2] This species is gray above, with darker saddles and scattered black spots that fade with age; the underside is off-white. [4]