The ocean sunfish, Mola mola, or common mola, is the heaviest known bony fish in the world. It has an average adult weight of 1,000 kg (2,200 lb). The species is native to tropical and temperate waters around the globe. It resembles a fish head with a tail, and its main body is flattened laterally. Sunfish can be as tall as they are long when their dorsal and ventral fins are extended. Adult sunfish are vulnerable to few natural predators, but sea lions, orcas and sharks will consume them. Among humans, sunfish are considered a delicacy in some parts of the world, including Japan, the Korean peninsula and Taiwan. In the course of its evolution, the caudal fin (tail) of the sunfish disappeared, to be replaced by a lumpy pseudo-tail, the clavus. This structure is formed by the convergence of the dorsal and anal fins. The smooth-denticled clavus retains twelve fin rays, and terminates in a number of rounded ossicles. Without a true tail to provide thrust for forward motion and equipped with only small pectoral fins, Mola mola relies on its long, thin dorsal and anal fins for propulsion, driving itself forward by moving these fins from side to side. Adult sunfish range from brown to silvery-gray or white, with a variety of mottled skin patterns; some of these patterns may be region-specific. Colouration is often darker on the dorsal surface, fading to a lighter shade ventrally as a form of counter-shading camouflage. Mola mola also exhibits the ability to vary skin colouration from light to dark, especially when under attack.