Megalodon

Otodus megalodon, meaning "big tooth" and commonly known as megalodon, was an extinct species of giant mackerel shark. It lived about 23 to 3.58 million years ago, from the Early Miocene to the Early Pliocene epochs. This prehistoric fish was once thought to belong to the family Lamnidae and to be a close relative of the great white shark. Scientists now place it in the extinct family Otodontidae. This family split off from the great white shark long ago, during the Early Cretaceous.

Megalodon is considered one of the largest and most powerful predators ever to live. We know it only from partly preserved remains, so scientists are not sure exactly what it looked like or how big it grew. Some scientists have debated whether its body was stockier or more slender than that of modern lamniform sharks. Estimates of its largest length range from 14.2 to 24.3 metres (47 to 80 ft). Most individuals are thought to have been about 10.5 metres (34 ft) long. Its teeth were thick and strong, made for grabbing prey and breaking bone.

Megalodon probably had a big effect on the structure of marine communities. Fossils show that it lived in many parts of the world. It probably hunted large animals, such as whales, seals, and sea turtles. Young megalodons lived in warm coastal waters and ate fish and small whales. Unlike the great white, which attacks from the soft underside of its prey, megalodon probably used its strong jaws to break through the chest and reach the heart and lungs.

The shark had to compete with whale-eating cetaceans, such as Livyatan and other macroraptorial sperm whales. Because it preferred warmer water, the cooling of the oceans that came with the start of the ice ages may have helped cause its decline. Falling sea levels, which reduced safe nursery areas, may also have played a part. A drop in the variety of baleen whales, along with a shift in their range toward the polar regions, may have reduced its main food source. The shark disappeared at the same time that baleen whales were growing to giant sizes. For other uses of the name, see Megalodon (disambiguation).

Classification

People have dug up megalodon teeth since ancient times. Pre-Columbian cultures in the Americas valued them for their large size and sharp, saw-like edges. They shaped the teeth into projectile points, knives, jewelry, and objects used in funerals. Pliny the Elder wrote about the teeth in AD 73 in Historia Naturalis. He described them as stone tongues that Roman people believed fell from the sky during lunar eclipses. Later, the Italian naturalist Fabio Colonna argued in 1616 that these stones were really shark teeth. He compared a megalodon tooth to a great white shark's tooth. In the late 1600s, Niels Steensen studied the head of a great white shark and also agreed that the stones were shark teeth. Swiss naturalist Louis Agassiz gave megalodon its scientific name in his work from 1833 to 1843. The name combines Greek words meaning "big" and "tooth."

The oldest megalodon remains come from the Late Oligocene, about 28 million years ago. Scientists still disagree about when this shark first appeared. People once thought megalodon died out around the end of the Pliocene, about 2.6 million years ago. A study from 2019 moved that date back to 3.6 million years ago. Megalodon was once placed in the same family as the great white shark. Today, it is considered part of the family Otodontidae, genus Otodus. Its teeth look like those of the great white shark most likely because of convergent evolution. This means the two sharks developed similar features separately.

Biology

Megalodon is known only from broken remains, so scientists are not sure exactly how it looked or how big it grew. One idea is that it was a sturdy shark, built a bit like the great white shark, with blunter and wider jaws, fins similar in shape but thicker, and small eyes set deep in its head. Another idea is that it looked more like the whale shark (Rhincodon typus) or the basking shark (Cetorhinus maximus). In that case, it had a crescent-shaped tail fin and a caudal keel on each side of the caudal peduncle, a shape that helps large animals reduce drag. In 2024, it was suggested that megalodon had a longer body than people first thought. In 2025, Shimada and colleagues supported this idea by comparing it with other laminforms and thresher sharks.

Size estimates vary because they come from fossil teeth and vertebrae, and the great white shark is the main guide for them. Estimates of its maximum total length range from 14.2 to 24.3 meters (47 to 80 ft). A 2015 study estimated its typical total body length at 10.5 meters (34 ft), while large great white sharks are usually about 6 meters (20 ft). The whale shark is the largest living fish.

Estimates have changed over time. The first jaw reconstruction was made by Bashford Dean in 1909 and was displayed at the American Museum of Natural History. Later studies by ichthyologist John E. Randall, who used enamel height, and by researchers including Leonard Compagno and Kenshu Shimada of DePaul University, also changed the picture. Researchers have also compared megalodon with living lamnid sharks and with the fin whale to estimate how fast it could swim.

Its large size may have been caused by its climate and by plenty of large prey. It may also have been linked to mesothermy, a state that would have increased its metabolic rate. Because otodontid sharks were thought to be ectotherms, megalodon was once thought to be ectothermic too. Other evidence, however, suggests it was probably a regional endotherm. In 2020, Shimada and colleagues suggested that males may have used claspers during mating.

Megalodon's most common fossils are its teeth. They are triangular, strong, large, and finely serrated, with a V-shaped neck where the root meets the crown. The teeth lacked lateral denticles and were held in place by connective tissue fibers. The rough base may have added to mechanical strength. Its teeth are the largest of any known shark species.

A nearly complete set of teeth was found in Saitama, Japan in 1989. Another near-complete set came from the Yorktown Formations in the United States. It helped build a jaw reconstruction at the National Museum of Natural History. Its dental formula was worked out in 1996, and the shark had over 250 teeth in five rows.

In 2008, researchers led by S. Wroe estimated its bite force at between 108,514 and 182,201 newtons. This was far stronger than the bite of the largest confirmed great white. They compared it with that of the placoderm fish Dunkleosteus. In 2021, Antonio Ballell and Humberto Ferrón used Finite Element Analysis to study stress in the teeth. They suggested the shape of the teeth may have come from heterochronic selection, which increased body size.

Megalodon is known from the fossil record through its teeth, vertebral centra, and coprolites. Like all sharks, its skeleton was made of cartilage rather than bone, so most fossils are poorly preserved. Its jaws and chondrocranium were more massive and sturdy than those of the great white. Partial vertebrae were found in the Antwerp Basin in Belgium in 1926 and in the Gram Formation in Denmark in 1983. Spiral-shaped coprolites suggest a spiral valve in the lower intestines. Miocene coprolites were found in Beaufort County, South Carolina.

A reconstructed skeleton, 11.3 meters (37 ft) long, was built by Gottfried and colleagues. It is displayed at the Calvert Marine Museum in the United States and the Iziko South African Museum. It represents a mature male, based on ontogenetic changes seen in great white sharks.

Paleobiology

Most sharks eat whatever they can find. Megalodon was different. Its great size, fast swimming, powerful jaws, and strong teeth made it a top hunter that could eat many kinds of animals. Chemical studies of calcium isotopes and nitrogen isotopes suggest it ate higher on the food chain than the great white shark that lived at the same time, though scientists disagree on how much higher. Tooth wear on Mediterranean megalodon specimens from the Miocene shows a very mixed diet, like that of modern great white sharks. Fossils show that it hunted many whales, including dolphins, cetotheres, squalodontids (shark-toothed dolphins), physeteroidea, bowhead whales, fin whales, and blue whales. It also ate seals, sirenians, sea turtles, and smaller fish and sharks. Whale bones with deep marks and megalodon teeth found near chewed whale remains support this. A 2022 study of physeteroids, including Scaphokogia and the holotypes of Acrophyseter deinodon and Livyatan melvillei, found shark bite marks, some with serrations. The bite marks on the Livyatan skull were in an area only scavengers could reach, and the authors did not name the shark. Its diet changed with age and place. Adults off Peru probably hunted cetothere whales about 2.5 to 7 meters (8.2 to 23 ft) long and smaller prey, while young megalodon likely ate more fish.

Megalodon probably aimed for the heart and lungs of large whales. Great white sharks usually go for the underbelly instead. Its thick teeth were built for biting through tough bone. Small whale fossils with compression fractures suggest they were hit from below before being eaten. Large Pliocene whales have flipper bones and tail vertebrae with bite marks, which suggests megalodon stopped them from moving before feeding. It hunted eurhinodelphinids in a similar way. Its diet may also have included basking sharks of the family Cetorhinidae. Young megalodon were likely small enough to be attacked by the great hammerhead shark and the snaggletooth shark. Later studies suggest they were about 4 meters (13 ft) long, which kept them safer from enemies. Their diet changed as they grew, an ontogenetic shift. Young megalodon ate fish, sea turtles, dugongs, and small whales. Adults moved offshore and ate large whales. Nursery areas have been found in the Gatún Formation, the Calvert Formation, the Canary Islands, and the Bone Valley Formation. Megalodon grew quickly, nearly two times as fast as the great white shark, according to a 2010 estimate by Ehret. Its growth seems to have slowed around 25 years of age. A 2021 study estimated lifespans of 88 to 100 years.

Paleoecology

Megalodon lived in many parts of the world. Its fossils have been dug up in Europe, Africa, the Americas, and Australia. It most often lived in subtropical to temperate latitudes. One report placed it as far north as 78° N, but that record is probably doubtful. Scientists think it could handle water temperatures from 1–24 °C (34–75 °F). This may be because large sharks can keep their bodies warmer than the water by holding in metabolic heat.

Megalodon lived in many ocean places. These included shallow coastal waters, areas of upwelling, swampy coastal lagoons, sandy littorals, and deep offshore waters. Adults mostly stayed offshore. They may have moved between coastal and open ocean waters at different stages of life. The most typical (modal) length was estimated at 10.5 meters (34 ft).

A 2023 study looked at fossils from the Late Miocene of the western Pacific and the Early Pliocene of the eastern Atlantic. It suggested that megalodon followed Bergmann's rule, meaning larger animals live in colder waters. A 2026 re-check did not find a clear link to sea temperature. Instead, it suggested that places with small fossils were nurseries for young sharks. Another 2026 study found few size differences between Atlantic and Mediterranean populations. The one exception was a Miocene site in Spain, which was likely a nursery. Megalodon's fossils have been found in oceans all around the world during the Neogene.

Megalodon was at the top of the food chain, which probably shaped the ocean life around it. Fossil evidence links it to the emergence and spread of whales and other sea mammals. Young megalodon preferred places with many small whales. Adults preferred places with many large whales.

It lived at the same time as other whale-eating toothed whales, including macroraptorial sperm whales and squalodontidae. These were also top predators, so they competed with megalodon. Some grew very large, like Livyatan, which was estimated at 13.5 to 17.5 meters (44 to 57 ft). Megalodon likely hunted Zygophyseter, another macroraptorial sperm whale.

By about 11 million years ago, these macroraptorial whales had declined sharply, which reduced competition. Earlier ideas that killer whales became strong rivals are now doubted. The oldest known Orcinus citoniensis hunted small fish and squid rather than sea mammals. Megalodon may have pushed out other sharks, which mostly stayed in colder waters. In places like Pliocene Baja California, megalodon and the great white shark may have visited at different times of year to follow different prey. Megalodon probably also ate its own kind, as many sharks do today (cannibalism).

Extinction

Many changes on Earth affected sea life while megalodon lived. The oceans cooled, and ice grew at the poles. Events such as the closure of the Central American Seaway and changes in the Tethys Ocean helped cool the seas. The slowing of the Gulf Stream kept nutrient-rich water from reaching major ocean areas. This may have made food harder to find for megalodon. During the Plio-Pleistocene, part of the Cenozoic era, sea levels dropped a lot as glaciers grew. This may have made it harder for megalodon to find shallow, warm waters to raise its young. Temperature change does not seem to have directly caused its extinction, because megalodon lived in a wide range of water temperatures. This fits with evidence that it was a mesotherm.

Many mysticetes, or baleen whales, had died out by the end of the Miocene. Megalodon may have depended on these whales for food, so their decline may have affected it. A large die-off in the Pliocene also wiped out many big sea animals. Some scientists once thought that dolphin-like relatives, the genus Orcinus (including Orcinus citoniensis), had competed with megalodon, but this idea is disputed. Paleontologist Robert Boessenecker and his colleagues estimated that megalodon became extinct about 3.51 million years ago. They suggested that climate shifts and competition with modern white sharks may have played a part. Megalodon may also have become coextinct with smaller whales, such as Piscobalaena nana.

In popular culture

Megalodon appears in many stories, including films and books. It is still a popular subject for sea monsters stories. Some people believed megalodon might still be alive because of teeth that seemed fresh. HMS Challenger found these teeth in 1873. In 1959, the zoologist Wladimir Tschernezky found that the teeth were about 11,000 to 24,000 years old. This helped spread the idea that megalodon still lived, among cryptozoologists. Scientists have since shown that these claims are not true. The teeth were likely kept well preserved by a thick crust of precipitate made of manganese dioxide. This crust slowed their decomposition rate and kept them white during fossilization. Fossil megalodon teeth can be off-white, dark brown, grey, or blue. Some may have moved into a younger stratum. Some people think megalodon could hide in the deep sea, like the megamouth shark found in 1976. This is unlikely. The megamouth lived in warm coastal waters and probably could not survive in the cold, low-food deep sea environment. Reports of megalodon sightings are most likely hoaxes or mistakes with the whale shark, which looks similar in many ways.

Stories about megalodon surviving into modern times began with the 1997 novel Meg: A Novel of Deep Terror by Steve Alten and its sequels. Films followed, such as the 2002 direct-to-video Shark Attack 3: Megalodon. The Meg came out in 2018 and was based on the book. It was a big success at the box office. Animal Planet made the pseudo-documentary Mermaids: The Body Found, which showed a meeting between mermaids and a megalodon about 1.6 million years ago. In August 2013, the Discovery Channel started its yearly Shark Week series with Megalodon: The Monster Shark Lives. This docufiction was criticized because it was completely made up, and it did not clearly say so. Megalodon is the official state shark of Maryland. Its teeth are the state fossil of North Carolina.