Sand tiger shark

Its snout is short and pointed, its eyes are small, its teeth are spear-shaped and protrude forward, and its dorsal and anal fins are small and of equal size; the first dorsal fin is positioned closer to the anal fins than to the pectoral fins. The upper lobe of the caudal fin has a pronounced notch, and the lower lobe is short. Its color is pale brown or gray, gradually lightening toward the belly, and it is dotted with dark spots, which are barely visible in adult specimens. The fins are dull and have a matte sheen. It is often found near the coast on the seabed or close to the bottom; less frequently, it swims into open water and the water layers below the surface. It is the only known shark species capable of swallowing air and storing it in its stomach to ensure adequate buoyancy while swimming. It roams the ocean either alone or in small to large groups, feeding on bony fish, smaller sharks, rays, squid, and crabs. It is a migratory species; in summer, it migrates toward the poles, thus spending most of its migration range at the northern and southern edges, while in fall and winter, it swims toward the Equator. Its reproduction is unique because in the two-chambered uterus, the embryos that develop earliest consume the other eggs and their younger siblings. Thus, a total of two offspring are born. Scientists hypothesize that this so-called intrauterine cannibalism evolved because it results in larger and stronger offspring that are more viable and better able to survive in their wild environment.