Megalodon

Megalodon (/ˈmɛɡələdɒn/ MEG-ə-lə-don; meaning "big tooth", from Ancient Greek: μέγας (megas) “big, mighty” + ὀδόν (odon) (from ὀδούς (odous) "tooth")),[1] is an extinct species of shark that lived approximately 28 to 1.5 million years ago, during the Cenozoic Era (late Oligocene to early Pleistocene).

The taxonomic assignment of C. megalodon has been debated for nearly a century, and is still under dispute. The two major interpretations are Carcharodon megalodon (under family Lamnidae) or Carcharocles megalodon (under the family Otodontidae).[2] Consequently, the scientific name of this species is commonly abbreviated C. megalodon in the literature.

C. megalodon is regarded as one of the largest and most powerful predators in vertebrate history,[3] and likely had a profound impact on the structure of marine communities.[4] Fossil remains suggest that this giant shark reached a maximum length of 14–18 metres (46–59 ft),[3] and also affirm that it had a cosmopolitan distribution.[2] Scientists suggest that C. Megalodon looked like a stockier version of the great white shark, Carcharodon carcharias.

Glossopterae
According to Renaissance accounts, gigantic, triangular fossil teeth often found embedded in rocky formations were once believed to be the petrified tongues, or glossopetrae, of dragons and snakes. This interpretation was corrected in 1667 by Danish naturalist Nicolaus Steno, who recognized them as shark teeth, and famously produced a depiction of a shark's head bearing such teeth.[6] He described his findings in the book The Head of a Shark Dissected, which also contained an illustration of a C. megalodon tooth.

Identification
Swiss naturalist Louis Agassiz gave the shark its initial scientific name, Carcharodon megalodon, in 1835,[8] in his research work Recherches sur les poissons fossiles[9] (Research on fossil fish), which he completed in 1843. Megalodon teeth are morphologically similar to the teeth of the great white shark. On the basis of this observation, Agassiz assigned megalodon to the genus Carcharodon.[8] While the scientific name is C. megalodon, it is often informally dubbed the "megatooth shark",[5] "giant white shark"[10] or "monster shark".

Fossils
C. megalodon is represented in the fossil record primarily by teeth and vertebral centra.[5] As with all sharks, C. megalodon's skeleton was formed of cartilage rather than bone; this results in mostly poorly preserved fossil specimens.

Teeth
The most common megalodon fossils are its teeth. Diagnostic characteristics include: triangular shape,[2] robust structure,[5] large size,[2] fine serrations,[2] and visible v-shaped neck.[2] Megalodon teeth can measure over 180 millimetres (7.1 in) in slant height or diagonal length, and are the largest in size of any known shark species.

Vertebrae
Some fossil vertebrae have been found.[7] The most notable example is a partially preserved vertebral column of a single specimen, excavated in the Antwerp basin, Belgium by M. Leriche in 1926. It comprises 150 vertebral centra, with the centra ranging from 55 millimetres (2.2 in) to 155 millimetres (6.1 in) in diameter.[5] However, scientists have claimed that considerably larger vertebral centra can be expected.[5] A partially preserved vertebral column of another megalodon specimen was excavated from Gram clay, Denmark by Bendix-Almgeen in 1983. This specimen comprises 20 vertebral centra, with the centra ranging from 100 millimetres (3.9 in) to 230 millimetres (9.1 in) in diameter.

Distribution and age
C. megalodon fossils have been excavated from many parts of the world, including Europe, Africa and both North and South America,[5][7] as well as Puerto Rico,[15] Cuba,[16] Jamaica,[17] Canary Islands,[18] Australia,[19] New Zealand,[13] Japan,[5][7] Malta,[13] Grenadines[20] and India.[7] Megalodon teeth have been excavated from regions far away from continental lands, such as the Mariana Trench in the Pacific Ocean.[13]

The earliest megalodon remains were reported from late Oligocene strata, circa 28 million years old.[21][22] Although fossils are mostly absent in strata extending beyond the Tertiary boundary,[5] they have been reported from subsequent Pleistocene strata.[23] It is believed that C. megalodon became extinct in the Pleistocene, probably about 1.5 million years ago.