when did the great white shark first appear
Great white shark The earliest known fossils of the great white shark are about 16 million years old, during the mid-Miocene epoch.[1] However, the phylogeny of the great white is still in dispute. The original hypothesis for the great white's origins is that it shares a common ancestor with a prehistoric shark, such as the C. megalodon. C. megalodon had teeth that were superficially not too dissimilar with those of great white sharks, but its teeth were far larger. Although cartilaginous skeletons do not fossilize, C. megalodon is estimated to have been considerably larger than the great white shark, estimated at up to 17 m (56 ft) and 59,413 kg (130,983 lb).[21] Similarities among the physical remains and the extreme size of both the great white and C. megalodon led many scientists to believe these sharks were closely related, and the name Carcharodon megalodon was applied to the latter. However, a new hypothesis proposes that the C. megalodon and the great white are distant relatives (albeit sharing the family Lamnidae). The great white is also more closely related to an ancient mako shark, Isurus hastalis, than to the C. megalodon, a theory that seems to be supported with the discovery of a complete set of jaws with 222 teeth and 45 vertebrae of the extinct transitional species Carcharodon hubbelli in 1988 and published on 14 November 2012.[22] In addition, the new hypothesis assigns C. megalodon to the genus Carcharocles, which also comprises the other megatoothed sharks; Otodus obliquus is the ancient representative of the extinct Carcharocles lineage.[23]
Frilled shark The frilled shark (Chlamydoselachus anguineus) is one of two extant species of shark in the family Chlamydoselachidae, with a wide but patchy distribution in the Atlantic and Pacific Oceans. This species is found over the outer continental shelf and upper continental slope, generally near the bottom, though there is evidence of substantial upward movements. It has been caught as deep as 1,570 m (5,150 ft), although it is uncommon below 1,200 m (3,900 ft).[2] In Suruga Bay, Japan, it is most common at depths of 50–200 m (160–660 ft). Exhibiting several primitive features, the frilled shark has often been termed a living fossil. It reaches a length of 2 m (6.6 ft) and has a dark brown, eel-like body with the dorsal, pelvic, and anal fins placed far back. Its common name comes from the frilly or fringed appearance of its six pairs of gill slits, with the first pair meeting across the throat.