megalodon

Classification

Prescientific and early research history

Megalodon teeth have been excavated and used since ancient times. They were a valued artifact amongst pre-Columbian cultures in the Americas for their large sizes and serrated blades, from which they were modified into projectile points, knives, jewelry, and funeral accessories. At least some, such as the Sitio Conte societies of Panama, seemed to have used them primarily for ceremonial purposes. Mining of megalodon teeth by the Algonquian peoples in the Chesapeake Bay and their selective trade with the Adena culture in Ohio occurred as early as 430 BC. The earliest written account of megalodon teeth was by Pliny the Elder in an AD 73 volume of Historia Naturalis, who described them as resembling petrified human tongues that Roman folklorists believed to have fallen from the sky during lunar eclipses and called them glossopetrae ("tongue stones"). The purported tongues were later thought in a 12th-century Maltese tradition to have belonged to serpents that Paul the Apostle turned to stone while shipwrecked there, and were given antivenom powers by the saint. Glossopetrae reappeared throughout Europe in late 13th to 16th century literature, ascribed with more supernatural properties that cured a wider variety of poisons. Use of megalodon teeth for this purpose became widespread among medieval and Renaissance nobility, who fashioned them into protective amulets and tableware to purportedly detoxify poisoned liquids or bodies that touched the stones. By the 16th century, teeth were directly consumed as ingredients of European-made Goa stones.

The true nature of the glossopetrae as shark's teeth was held by some since at least 1554, when cosmographer André Thevet described it as hearsay, although he did not believe it. The earliest scientific argument for this view was made by Italian naturalist Fabio Colonna, who in 1616 published an illustration of a Maltese megalodon tooth alongside a great white shark's and noted their striking similarities. He argued that the former and its likenesses were not petrified serpent's tongues but actually the teeth of similar sharks that washed up on shore. Colonna supported this thesis through an experiment of burning glossopetrae samples, from which he observed carbon residue he interpreted as proving an organic origin. However, interpretation of the stones as shark's teeth remained widely unaccepted. This was in part due to the inability to explain how some of them are found far from the sea. The shark tooth argument was academically raised again during the late 17th century by English scientists Robert Hooke, John Ray, and Danish naturalist Niels Steensen (Latinized Nicholas Steno). Steensen's argument in particular is most recognized as inferred from his dissection of the head of a great white caught in 1666. His 1667 report depicted engravings of a shark's head and megalodon teeth that became especially iconic. However, the illustrated head was not actually the head that Steensen dissected, nor were the fossil teeth illustrated by him. Both engravings were originally commissioned in the 1590s by Papal physician Michele Mercati, who also had in possession the head of a great white, for his book Metallotheca. The work remained unpublished in Steensen's time due to Mercati's premature death, and the former reused the two illustrations per suggestion by Carlo Roberto Dati, who thought a depiction of the actual dissected shark was unsuitable for readers. Steensen also stood out in pioneering a stratigraphic explanation for how similar stones appeared further inland. He observed that rock layers bearing megalodon teeth contained marine sediments and hypothesized that these layers correlated to a period of flood that was later covered by terrestrial layers and uplifted by geologic activity.

Evolution

While the earliest megalodon remains have been reported from the Late Oligocene, around 28 million years ago (Mya), there is disagreement as to when it appeared, with dates ranging to as young as 16 Mya. It has been thought that megalodon became extinct around the end of the Pliocene, about 2.6 Mya; claims of Pleistocene megalodon teeth, younger than 2.6 million years old, are considered unreliable. A 2019 assessment moves the extinction date back to earlier in the Pliocene, 3.6 Mya.

Megalodon is considered to be a member of the family Otodontidae, genus Otodus, as opposed to its previous classification into Lamnidae, genus Carcharodon. Megalodon's classification into Carcharodon was due to dental similarity with the great white shark, but most authors believe that this is due to convergent evolution. In this model, the great white shark is more closely related to the extinct broad-toothed mako (Cosmopolitodus hastalis) than to megalodon, as evidenced by more similar dentition in those two sharks; megalodon teeth have much finer serrations than great white shark teeth. The great white shark is more closely related to the mako sharks (Isurus spp.), with a common ancestor around 4 Mya. Proponents of the former model, wherein megalodon and the great white shark are more closely related, argue that the differences between their dentition are minute and obscure.

The genus Carcharocles contains four species: C. auriculatus, C. angustidens, C. chubutensis, and C. megalodon. The evolution of this lineage is characterized by the increase of serrations, the widening of the crown, the development of a more triangular shape, and the disappearance of the lateral cusps. The evolution in tooth morphology reflects a shift in predation tactics from a tearing-grasping bite to a cutting bite, likely reflecting a shift in prey choice from fish to cetaceans. Lateral cusplets were finally lost in a gradual process that took roughly 12 million years during the transition between C. chubutensis and C. megalodon. The genus was proposed by D. S. Jordan and H. Hannibal in 1923 to contain C. auriculatus. In the 1980s, megalodon was assigned to Carcharocles. Before this, in 1960, the genus Procarcharodon was erected by French ichthyologist Edgard Casier, which included those four sharks and was considered separate from the great white shark. It is since considered a junior synonym of Carcharocles. The genus Palaeocarcharodon was erected alongside Procarcharodon to represent the beginning of the lineage, and, in the model wherein megalodon and the great white shark are closely related, their last common ancestor. It is believed to be an evolutionary dead-end and unrelated to the Carcharocles sharks by authors who reject that model.

Biology

Appearance

One interpretation on how megalodon appeared was that it was a robust-looking shark, and may have had a similar build to the great white shark. The jaws may have been blunter and wider than the great white, and the fins would have also been similar in shape, though thicker due to its size. It may have had a pig-eyed appearance, in that it had small, deep-set eyes.

Another interpretation is that megalodon bore a similarity to the whale shark (Rhincodon typus) or the basking shark (Cetorhinus maximus). The tail fin would have been crescent-shaped, the anal fin and second dorsal fin would have been small, and there would have been a caudal keel present on either side of the tail fin (on the caudal peduncle). This build is common in other large aquatic animals, such as whales, tuna, and other sharks, in order to reduce drag. The head shape can vary between species as most of the drag-reducing adaptations are toward the tail-end of the animal.

It was suggested in 2024 that megalodon had a more elongated body plan than previously thought. Shimada et al. (2025) also supported this hypothesis based on comparing the proportions of the neurocranium and caudal fin relative to its trunk to those of other laminforms (excluding goblin sharks and thresher sharks). They estimated that the maximum body length of megalodon would have been significantly longer than previously published estimates.

In 2023, Shimada and colleagues reported the associated set of megalodon remains found with placoid scales, which are 0.3 to 0.8 millimetres (0.012 to 0.031 in) in maximum width, and have broadly spaced keels. The quantitative relationship of the distance between each keel and the reported maximum cruising speeds of modern sharks were consistent with the hypothesis that megalodon was regionally endothermic but generally not a fast swimmer, though it may have been capable of occasional burst swimming to capture prey.

Size

Due to fragmentary remains, there have been many contradictory size estimates for megalodon, as they can only be drawn from fossil teeth and vertebrae. The great white shark has been the basis of reconstruction and size estimation, as it is regarded as the best analogue to megalodon. Several total length estimation methods have been produced from comparing megalodon teeth and vertebrae to those of the great white.

Size estimates of megalodon vary depending on the method used and the hypothesis of its body plan, with maximum total length estimates ranging from 14.2–24.3 meters (47–80 ft). Gottfried (1996) suggested that mature male megalodon may have had a body mass of 12.6 to 33.9 t (13.9 to 37.4 short tons; 12.4 to 33.4 long tons), and mature females may have been 27.4 to 59.4 t (30.2 to 65.5 short tons; 27.0 to 58.5 long tons), assuming that males could range in length from 10.5 to 14.3 meters (34 to 47 ft) and females 13.3 to 17 meters (44 to 56 ft). A 2015 study estimated the modal total body length at 10.5 meters (34 ft), calculated from 544 megalodon teeth, found throughout geological time and geography, including juveniles and adults ranging from 2.2 to 17.9 metres (7.2 to 58.7 ft) in total length. In comparison, large great white sharks are generally around 6 meters (20 ft) in length, with a few contentious reports suggesting larger sizes. The whale shark is the largest living fish, with one large female reported with a precaudal length of 15 meters (49 ft) and an estimated total length of 18.8 meters (62 ft). It is possible that different populations of megalodon around the globe had different body sizes and behaviors due to different ecological pressures. Megalodon is thought to have been the largest macropredatory shark that ever lived.

In 2020, Cooper and his colleagues reconstructed a 2D model of megalodon based on the dimensions of all the extant lamnid sharks and suggested that a 16 meters (52 ft) long megalodon would have had a 4.65 m (15.3 ft) long head, 1.41 m (4 ft 8 in) tall gill slits, a 1.62 m (5 ft 4 in) tall dorsal fin, 3.08 m (10 ft 1 in) long pectoral fins, and a 3.85 m (12 ft 8 in) tall tail fin. In 2022, Cooper and his colleagues also reconstructed a 3D model with the same basis as the 2020 study, resulting in a body mass estimate of 61.56 t (67.86 short tons; 60.59 long tons) for a 16 meters (52 ft) long megalodon, higher than the previous estimates. A 11.1 metres (36 ft) long vertebral column specimen IRSNB P 9893 (formerly IRSNB 3121) from Belgium, likely belonging to a 46 year old individual, was used for extrapolation. An individual of this size would have required 98,175 kcal per day, 20 times more than what the adult great white requires. Because the total body length of IRSNB P 9893 was previously estimated around 9.2 metres (30 ft), the longer body length estimate by Cooper et al. (2022) led to an alternative hypothesis that megalodon had a more elongated body form than previously thought based on comparison between IRSNB P 9893 and corresponding parts of the extant white sharks' vertebral columns. Shimada et al. (2025) also supported the elongated body plan hypothesis, and this resulted in a similar body length estimate of 16.4 metres (54 ft) and a significantly lower body mass estimate between 26.9–33.7 metric tons (29.7–37.1 short tons) for IRSNB P 9893. IRSNB P 9893 is considered as a mid-sized megalodon specimen.

Teeth and bite force

The most common fossils of megalodon are its teeth. Diagnostic characteristics include a triangular shape, robust structure, large size, fine serrations, a lack of lateral denticles, and a visible V-shaped neck (where the root meets the crown). The tooth met the jaw at a steep angle, similar to the great white shark. The tooth was anchored by connective tissue fibers, and the roughness of the base may have added to mechanical strength. The lingual side of the tooth, the part facing the tongue, was convex; and the labial side, the other side of the tooth, was slightly convex or flat. The anterior teeth were almost perpendicular to the jaw and symmetrical, whereas the posterior teeth were slanted and asymmetrical.

Megalodon teeth can measure over 180 millimeters (7.1 in) in slant height (diagonal length) and are the largest of any known shark species, implying it was the largest of all macropredatory sharks. In 1989, a nearly complete set of megalodon teeth was discovered in Saitama, Japan. Another nearly complete associated megalodon dentition was excavated from the Yorktown Formations in the United States, and served as the basis of a jaw reconstruction of megalodon at the National Museum of Natural History (USNM). Based on these discoveries, an artificial dental formula was put together for megalodon in 1996.

The dental formula of megalodon is: 2.1.7.43.0.8.4. As evident from the formula, megalodon had four kinds of teeth in its jaws: anterior, intermediate, lateral, and posterior. Megalodon's intermediate tooth technically appears to be an upper anterior and is termed as "A3" because it is fairly symmetrical and does not point mesially (side of the tooth toward the midline of the jaws where the left and right jaws meet). Megalodon had a very robust dentition, and had over 250 teeth in its jaws, spanning 5 rows. It is possible that large individuals had jaws spanning roughly 2 meters (6.6 ft) across. The teeth were also serrated, which would have improved efficiency in cutting through flesh or bone. The shark may have been able to open its mouth to a 75° angle, though a reconstruction at the USNM approximates a 100° angle.

In 2008, a team of scientists led by S. Wroe conducted an experiment to determine the bite force of the great white shark, using a 2.5-meter (8.2 ft) long specimen, and then isometrically scaled the results for its maximum size and the conservative minimum and maximum body mass of megalodon. They placed the bite force of the latter between 108,514 to 182,201 newtons (24,395 to 40,960 lbf) in a posterior bite, compared to the 18,216 newtons (4,095 lbf) bite force for the largest confirmed great white shark, and 7,495 newtons (1,685 lbf) for the placoderm fish Dunkleosteus. In addition, Wroe and colleagues pointed out that sharks shake sideways while feeding, amplifying the force generated, which would probably have caused the total force experienced by prey to be higher than the estimate.

Internal anatomy

Megalodon is represented in the fossil record by teeth, vertebral centra, and coprolites. As with all sharks, the skeleton of megalodon was formed of cartilage rather than bone; consequently most fossil specimens are poorly preserved. To support its large dentition, the jaws of megalodon would have been more massive, stouter, and more strongly developed than those of the great white, which possesses a comparatively gracile dentition. Its chondrocranium, the cartilaginous skull, would have had a blockier and more robust appearance than that of the great white. Its fins were proportional to its larger size.

Some fossil vertebrae have been found. The most notable example is a partially preserved vertebral column of a single specimen, excavated in the Antwerp Basin, Belgium, in 1926. It comprises 150 vertebral centra, with the centra ranging from 55 millimeters (2.2 in) to 155 millimeters (6 in) in diameter. The shark's vertebrae may have gotten much bigger, and scrutiny of the specimen revealed that it had a higher vertebral count than specimens of any known shark, possibly over 200 centra; only the great white approached it. Another partially preserved vertebral column of a megalodon was excavated from the Gram Formation in Denmark in 1983, which comprises 20 vertebral centra, with the centra ranging from 100 millimeters (4 in) to 230 millimeters (9 in) in diameter.

The coprolite remains of megalodon are spiral-shaped, indicating that the shark may have had a spiral valve, a corkscrew-shaped portion of the lower intestines, similar to extant lamniform sharks. Miocene coprolite remains were discovered in Beaufort County, South Carolina, with one measuring 14 cm (5.5 in).

Gottfried and colleagues reconstructed the entire skeleton of megalodon, which was later put on display at the Calvert Marine Museum in the United States and the Iziko South African Museum. This reconstruction is 11.3 meters (37 ft) long and represents a mature male, based on the ontogenetic changes a great white shark experiences over the course of its life.

Paleobiology

Prey relationships

Though sharks are generally opportunistic feeders, megalodon's great size, high-speed swimming capability, and powerful jaws, coupled with an impressive feeding apparatus, made it an apex predator capable of consuming a broad spectrum of animals. Otodus megalodon was probably one of the most powerful predators to have existed. Trophic level of megalodon have varied based on isotopic values. A study focusing on calcium isotopes of extinct and extant elasmobranch sharks and rays revealed that megalodon fed at a higher trophic level than the contemporaneous great white shark ("higher up" in the food chain). On the other hand, nitrogen isotopes found that megalodon's trophic level was at least two levels higher than the great white shark. However, the extremely high trophic levels of nitrogen isotopes has been viewed as problematic as there's little evidence to suggest Miocene food chains were significantly longer than those of today, at least during the Burdigalian. Including supplementary materials Zinc isotopic analysis revealed that megalodon saw a decrease in trophic level in the Atlantic Ocean during the early Pliocene. In North Carolina, megalodon and great white sharks have been noted to have an overlapping trophic level. A more recent analysis based on zinc isotopic values suggested megalodon was a opportunistic supercarnivore with high dietary flexibility at a population level.

Dental microwear of Mediterranean megalodon specimens from the Miocene shows that like modern great white sharks, it had a highly generalist diet that would have included invertebrates, marine mammals, marine reptiles, bony fish, and other elasmobranchs. Direct fossil evidence indicates that megalodon preyed upon many cetacean species, such as dolphins, small whales, cetotheres, squalodontids (shark toothed dolphins), physeteroidea inclusive macroraptorial, bowhead whales, and rorquals (such as fin whales and blue whales). In addition to this, they also targeted seals, sirenians, and sea turtles. The shark was an opportunist and piscivorous, and it would have also gone after smaller fish and other sharks. Many whale bones have been found with deep gashes most likely made by their teeth. Various excavations have revealed megalodon teeth lying close to the chewed remains of whales, and sometimes in direct association with them.

A 2022 study examined the remains of multiple physeteroids, specimens of both species of the Kogiid Scaphokogia as well as the holotypes of Acrophyseter deinodon and Livyatan melvellei, and discovered bite marks made by sharks on the examined specimens, some of which displayed serrations consistent with the teeth of either the modern great white shark or megalodon, though the authors of the paper refrained from a specific identification of the animal which caused the bite marks. The bite marks on the holotype of Livyatan are from a region of the skull which would have only been accessible to scavengers.

Feeding strategies

Sharks often employ complex hunting strategies to engage large prey animals. Great white shark hunting strategies may be similar to how megalodon hunted its large prey. Megalodon bite marks on whale fossils suggest that it employed different hunting strategies against large prey than the great white shark.

One particular specimen–the remains of a 9-meter (30 ft) long undescribed Miocene baleen whale–provided the first opportunity to quantitatively analyze its attack behavior. Unlike great whites which target the underbelly of their prey, megalodon probably targeted the heart and lungs, with their thick teeth adapted for biting through tough bone, as indicated by bite marks inflicted to the rib cage and other tough bony areas on whale remains. Furthermore, attack patterns could differ for prey of different sizes. Fossil remains of some small cetaceans, for example cetotheres, suggest that they were rammed with great force from below before being killed and eaten, based on compression fractures.

There is also evidence that a possible separate hunting strategy existed for attacking raptorial sperm whales; a tooth belonging to an undetermined 4 m (13 ft) physeteroid closely resembling those of Acrophyseter discovered in the Nutrien Aurora Phosphate Mine in North Carolina suggests that a megalodon or O. chubutensis may have aimed for the head of the sperm whale in order to inflict a fatal bite, the resulting attack leaving distinctive bite marks on the tooth. While scavenging behavior cannot be ruled out as a possibility, the placement of the bite marks is more consistent with predatory attacks than feeding by scavenging, as the jaw is not a particularly nutritious area to for a shark feed or focus on. The fact that the bite marks were found on the tooth's roots further suggest that the shark broke the whale's jaw during the bite, suggesting the bite was extremely powerful. The fossil is also notable as it stands as the first known instance of an antagonistic interaction between a sperm whale and an otodontid shark recorded in the fossil record.

During the Pliocene, larger cetaceans appeared. Megalodon apparently further refined its hunting strategies to cope with these large whales. Numerous fossilized flipper bones and tail vertebrae of large whales from the Pliocene have been found with megalodon bite marks, which suggests that megalodon would immobilize a large whale before killing and feeding on it.

Growth and reproduction

In 2010, Ehret estimated that megalodon had a fast growth rate nearly two times that of the extant great white shark. He also estimated that the slowing or cessation of somatic growth in megalodon occurred around 25 years of age, suggesting the species had an extremely delayed sexual maturity. In 2021, Shimada and colleagues calculated the growth rate of an approximately 9.2 m (30 ft) individual based on the Belgian vertebrate column specimen that presumably contains annual growth rings on three of its vertebrae. They estimated the individual died at 46 years of age, with a growth rate of 16 cm (6.3 in) per year, and a length of 2 m (6 ft 7 in) at birth. For a 15 m (49 ft) individual – which they considered the maximum attainable size – this would equate to a lifespan of 88 to 100 years. However, Cooper and his colleagues in 2022 estimated the length of this 46 year old individual at nearly 16 m (52 ft) based on the 3D reconstruction which resulted in the complete vertebral column to be 11.1 m (36 ft) long; the researchers claimed that this size estimate difference occurred due to the fact that Shimada and his colleagues extrapolated its size solely from the vertebral centra.

Megalodon, like contemporaneous sharks, made use of nursery areas to birth their young, specifically warm-water coastal environments with abundant food and protection from predators. Nursery sites were identified in the Gatún Formation of Panama, the Calvert Formation of Maryland, Banco de Concepción in the Canary Islands, the Bone Valley Formation of Florida and the Reverté Quarries of Spain. Shimada et al. (2023) conversely interpreted the proposed nurseries as evidence of Bergmann's rule, in which larger individuals are found in areas of colder climates and smaller individuals in areas of warmer climates. However, Ferrón et al. (2026) found no evidence of Bergmann's rule affecting O. megalodon populations, re-interpreting the small bodied fossils as indicative of nurseries. Given that all extant lamniform sharks give birth to live young, this is believed to have been true of megalodon also. Infant megalodons were around 3.5 meters (11 ft) at their smallest, and the pups were vulnerable to predation by other shark species, such as the great hammerhead shark (Sphyrna mokarran) and the snaggletooth shark (Hemipristis serra). Their dietary preferences display an ontogenetic shift: Young megalodon commonly preyed on fish, sea turtles, dugongs, and small cetaceans; mature megalodon moved to off-shore areas and consumed large cetaceans.

An exceptional case in the fossil record suggests that juvenile megalodon may have occasionally attacked much larger balaenopterid whales. Three tooth marks apparently from a 4-to-7-meter (13 to 23 ft) long Pliocene shark, likely a juvenile megalodon, were found on a rib from an ancestral blue or humpback whale that showed evidence of subsequent healing.

Paleoecology

Range and habitat

Megalodon had a cosmopolitan distribution. Fossils have been excavated from many parts of the world, including Europe, Africa, the Americas, and Australia. It most commonly occurred in subtropical to temperate latitudes. It has been found at latitudes up to 78° N; its inferred tolerated temperature range was 1–24 °C (34–75 °F). It arguably had the capacity to endure such low temperatures due to mesothermy, the physiological capability of large sharks to maintain a higher body temperature than the surrounding water by conserving metabolic heat.

Megalodon inhabited a wide range of marine environments (i.e., shallow coastal waters, areas of coastal upwelling, swampy coastal lagoons, sandy littorals, and offshore deep water environments) with a transient lifestyle. Adult megalodon were not abundant in shallow water environments, mostly inhabiting offshore areas. Megalodon may have moved between coastal and oceanic waters, particularly in different stages of its life cycle.

Fossil remains show a trend for specimens to be larger on average in the Southern Hemisphere than in the Northern, with mean lengths of 11.6 and 9.6 meters (38 and 31 ft), respectively; and also larger in the Pacific than the Atlantic, with mean lengths of 10.9 and 9.5 meters (36 and 31 ft) respectively. They do not suggest any trend of changing body size with absolute latitude, or of change in size over time (although the Otodus lineage in general is thought to display a trend of increasing size over time). The overall modal length has been estimated at 10.5 meters (34 ft), with the length distribution skewed towards larger individuals, suggesting an ecological or competitive advantage for larger body size.

Shimada et al. (2023) stated that, based on examined specimens of O. megalodon from the Late Miocene of the Western Pacific and Early Pliocene of the Eastern Atlantic, that it exhibited Bergmann's rule, that larger organisms are found in colder climates and smaller organisms in warmer climates. However, Ferrón et al. (2026) re-evaluated the dataset from the 2023 study and found no evidence of a significant relationship between sea-surface temperatures and body size in O. megalodon. Their analysis instead found the fossil assemblages supporting small-bodied specimens to be juvenile-dominated nurseries.

Herraiz et al. (2026) found no evidence of a significant differences of body size of members of Atlantic and Mediterranean populations other than the one known from the Miocene strata from the Reverté quarries of Spain, which was interpreted as a nursery.

Competition

Megalodon faced a highly competitive environment. Its position at the top of the food chain probably had a significant impact on the structuring of marine communities. Fossil evidence indicates a correlation between megalodon and the emergence and diversification of cetaceans and other marine mammals. Juvenile megalodon preferred habitats where small cetaceans were abundant, and adult megalodon preferred habitats where large cetaceans were abundant. Such preferences may have developed shortly after they appeared in the Oligocene.

Megalodon were contemporaneous with whale-eating toothed whales (particularly macroraptorial sperm whales and squalodontidae), which were also probably among the era's apex predators, and provided competition. Some attained gigantic sizes, such as Livyatan, estimated between 13.5 to 17.5 meters (44 to 57 ft). Fossilized teeth of an undetermined species of such physeteroids from Lee Creek Mine, North Carolina, indicate it had a maximum body length of 8 to 10 m (26 to 33 ft) and a maximum lifespan of about 25 years. This is very different from similarly sized modern killer whales that live to 65 years, suggesting that unlike the latter, which are apex predators, these physeteroids were subject to predation from larger species such as megalodon or Livyatan. Additionally, megalodon likely preyed on macroraptorial raptorial sperm whales such as Zygophyseter, which may suggest that it occupied a higher trophic level than extant apex predators, which is supported by calcium isotopic analysis.

By the Late Miocene, around 11 Mya, macroraptorials experienced a significant decline in abundance and diversity, leading to reduced competition. Traditionally it was assumed that cetaceans posed increased competition during the Pliocene due to the evolution of highly social, pack-hunting Orcinus, but this is now considered questionable as the oldest known species of Orcinus, Orcinus citoniensis, was specialized for preying on small fishes and cephalopods rather than pack hunting of marine mammals.

Megalodon may have subjected contemporaneous white sharks to competitive exclusion, as the fossil records indicate that other shark species avoided regions it inhabited by mainly keeping to the colder waters. In areas where their ranges seemed to have overlapped, such as in Pliocene Baja California, it is possible that megalodon and the great white shark occupied the area at different times of the year while following different migratory prey. Megalodon probably also had a tendency for cannibalism, much like contemporary sharks.

Extinction

Climate change

The Earth experienced a number of changes during the time period megalodon existed which affected marine life. A cooling trend starting in the Oligocene 35 Mya ultimately led to glaciation at the poles. Geological events changed currents and precipitation; among these were the closure of the Central American Seaway and changes in the Tethys Ocean, contributing to the cooling of the oceans. The stalling of the Gulf Stream prevented nutrient-rich water from reaching major marine ecosystems, which may have negatively affected its food sources. The largest fluctuation of sea levels in the Cenozoic era occurred in the Plio-Pleistocene, between around 5 million to 12 thousand years ago, due to the expansion of glaciers at the poles, which negatively impacted coastal environments, and may have contributed to its extinction along with those of several other marine megafaunal species. These oceanographic changes, in particular the sea level drops, may have restricted many of the suitable shallow warm-water nursery sites for megalodon, hindering reproduction. Nursery areas are pivotal for the survival of many shark species, in part because they protect juveniles from predation.

As its range did not apparently extend into colder waters, megalodon may not have been able to retain a significant amount of metabolic heat, so its range was restricted to shrinking warmer waters. Fossil evidence confirms the absence of megalodon in regions around the world where water temperatures had significantly declined during the Pliocene. However, an analysis of the distribution of megalodon over time suggests that temperature change did not play a direct role in its extinction. Its distribution during the Miocene and Pliocene did not correlate with warming and cooling trends; while abundance and distribution declined during the Pliocene, megalodon did show a capacity to inhabit colder latitudes. It was found in locations with a mean temperature ranging from 12 to 27 °C (54 to 81 °F), with a total range of 1 to 33 °C (34 to 91 °F), indicating that the global extent of suitable habitat should not have been greatly affected by the temperature changes that occurred. This is consistent with evidence that it was a mesotherm.

Changing ecosystem

Marine mammals attained greatest diversity during the Miocene, such as with baleen whales with over 20 recognized Miocene genera in comparison to only six extant genera. Such diversity presented an ideal setting to support a super-predator such as megalodon. By the end of the Miocene, many species of mysticetes had gone extinct; surviving species may have been faster swimmers and thus more elusive prey. Furthermore, after the closure of the Central American Seaway, tropical whales decreased in diversity and abundance. The extinction of megalodon correlates with the decline of many small mysticete lineages, and it is possible that it was highly dependent on them as a food source. Additionally, a marine megafauna extinction during the Pliocene was discovered to have eliminated 36% of all large marine species including 55% of marine mammals, 35% of seabirds, 9% of sharks, and 43% of sea turtles. The extinction was selective for endotherms and mesotherms relative to poikilotherms, implying causation by a decreased food supply and thus consistent with megalodon being mesothermic. Megalodon may have been too large to sustain itself on the declining marine food resources. The cooling of the oceans during the Pliocene might have restricted the access of megalodon to the polar regions, depriving it of the large whales which had migrated there.

Traditionally, competition from large odontocetes, such as macropredatory sperm whales or genus Orcinus (i.e., Orcinus citoniensis) in the Pliocene, was assumed to have contributed to the decline and extinction of megalodon. But this assumption is disputed due to being based on unsupported assumptions about when cetacean competitors were present: The Orcininae emerged in mid-Pliocene with O. citoniensis reported from the

Pliocene of Italy, and similar forms reported from the Pliocene of England and South Africa, indicating the capacity of these dolphins to cope with increasingly prevalent cold water temperatures in high latitudes. These dolphins were assumed to have been macrophagous in some studies, but it was found that early Orcinus were not macrophagous and fed on small fishes instead, thus posing minimal competition with even neonate O. megalodon. On the other hand, giant macropredatory sperm whales such as Livyatan-like forms are last reported from Australia and South Africa circa 5 million years ago, and smaller macroraptorial sperm whales like Acrophyseter also last appear in the fossil record at around this time, indicating that macroraptorial sperm whales died out earlier than O. megalodon. Certain physeteroids such as Hoplocetus and Scaldicetus survived longer into the Pliocene, but only the Miocene species attributed to these genera are considered macroraptorial. Members of genus Orcinus became large and macrophagous only in the Pleistocene, well after the extinction of O. megalodon.

In popular culture

Megalodon has been portrayed in many works of fiction, including films and novels, and continues to be a popular subject for fiction involving sea monsters. Reports of supposedly fresh megalodon teeth, such as those found by HMS Challenger in 1873 which were dated in 1959 by the zoologist Wladimir Tschernezky to be around 11,000 to 24,000 years old, helped popularise claims of recent megalodon survival amongst cryptozoologists. These claims have been discredited, and are probably teeth that were well-preserved by a thick mineral-crust precipitate of manganese dioxide, and so had a lower decomposition rate and retained a white color during fossilization. Fossil megalodon teeth can vary in color from off-white to dark browns, greys, and blues, and some fossil teeth may have been redeposited into a younger stratum. The claims that megalodon could remain elusive in the depths, similar to the megamouth shark which was discovered in 1976, are unlikely as the shark lived in warm coastal waters and probably could not survive in the cold and nutrient-poor deep sea environment. Alleged sightings of the megalodon have been noted to be likely hoaxes or misidentifications of the whale shark, which shared many visual characteristics with megalodon sightings.

Contemporary fiction about megalodon surviving into modern times was pioneered by the 1997 novel Meg: A Novel of Deep Terror by Steve Alten and its subsequent sequels. Megalodon subsequently began to feature in films, such as the 2002 direct to video Shark Attack 3: Megalodon, and later The Meg, a 2018 film based on the 1997 book which grossed over $500 million at the box office.

Animal Planet's pseudo-documentary Mermaids: The Body Found included an encounter 1.6 Mya between a pod of mermaids and a megalodon. Later, in August 2013, the Discovery Channel opened its annual Shark Week series with another film for television, Megalodon: The Monster Shark Lives, a controversial docufiction about the creature that presented alleged evidence in order to suggest that megalodons still lived. This program received criticism for being completely fictional and for inadequately disclosing its fictional nature; for example, all of the supposed scientists depicted were paid actors, and there was no disclosure in the documentary itself that it was fictional. In a poll by Discovery, 73% of the viewers of the documentary thought that megalodon was not extinct. In 2014, Discovery re-aired The Monster Shark Lives, along with a new one-hour program, Megalodon: The New Evidence, and an additional fictionalized program entitled Shark of Darkness: Wrath of Submarine, resulting in further backlash from media sources and the scientific community. Despite the criticism from scientists, Megalodon: The Monster Shark Lives was a huge ratings success, gaining 4.8 million viewers, the most for any Shark Week episode up to that point.