Megalodon

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. of megalodon teeth by the Algonquin peoples in the Chesapeake Bay and their selective trade with the Adena culture in Ohio occurred as early as 430 BC. 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 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 The work remained unpublished in Steensen's time due to Mercati's premature death, and the former reused the two illustrations per suggestion by Carlo Roberto Dati, who thought a depiction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. combined meaning "big tooth". Agassiz referenced the name as early as 1832, but because specimens were not referenced they are not taxonomically recognized uses. Because Carcharodon megalodon appeared first in the 1835 illustration, the remaining names are considered junior synonyms under the principle of priority. 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. 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. teeth|alt=A black megalodon tooth and two white great white shark teeth above a centimeter scale, the megalodon tooth extends between the zero and thirteen-and-a-half centimeter marks. One great white tooth extends between the eleven and thirteen centimeter marks, and the other extends between from the thirteen and sixteen centimeter marks. The genus Carcharocles contains four species: C. auriculatus, C. angustidens, 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. Some authors suggest that C. auriculatus, C. angustidens, and C. chubutensis should be classified as a single species in the genus Otodus, leaving C. megalodon the sole member of Carcharocles. A 2006 review of Chondrichthyes elevated Megaselachus to genus, and classified the sharks as Megaselachus megalodon and M. chubutensis. The discovery of fossils assigned to the genus Megalolamna in 2016 led to a re-evaluation of Otodus, which concluded that it is paraphyletic, that is, it consists of a last common ancestor but it does not include all of its descendants. The inclusion of the Carcharocles sharks in Otodus would make it monophyletic, with the sister clade being Megalolamna. ==Biology==

Appearance '' and modern lamnids 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. In 2023, Shimada and colleagues reported the associated set of megalodon remains found with placoid scales, which are 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. In comparison, large great white sharks are generally around in length, with a few contentious reports suggesting larger sizes. It is possible that different populations of megalodon around the globe had different body sizes and behaviors due to different ecological pressures. 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 for a long megalodon, higher than the previous estimates. A 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 , Shimada et al. (2025) also supported the elongated body plan hypothesis, and this resulted in a similar body length estimate of and a significantly lower body mass estimate between for IRSNB P 9893. In 2022, Cooper and his colleagues converted this calculation into relative cruising speed (body lengths per second), resulting in a mean absolute cruising speed of and a mean relative cruising speed of 0.09 body lengths per second for a long megalodon; the authors found their mean absolute cruising speed to be faster than any extant lamnid sharks and their mean relative cruising speed to be slower, consistent with previous estimates. In 2020, Shimada and colleagues suggested large size was instead due to intrauterine cannibalism, where the larger fetus eats the smaller fetus, resulting in progressively larger and larger fetuses, requiring the mother to attain even greater size as well as caloric requirements which would have promoted endothermy. Males would have needed to keep up with female size in order to still effectively copulate (which probably involved latching onto the female with claspers, like modern cartilaginous fish). Maximum estimates The first attempt to reconstruct the jaw of megalodon was made by Bashford Dean in 1909, displayed at the American Museum of Natural History. From the dimensions of this jaw reconstruction, it was hypothesized that megalodon could have approached in length. Dean had overestimated the size of the cartilage on both jaws, causing it to be too tall. In 1973, John E. Randall, an ichthyologist, used the enamel height (the vertical distance of the blade from the base of the enamel portion of the tooth to its tip) to measure the length of the shark, yielding a maximum length of about . However, tooth enamel height does not necessarily increase in proportion to the animal's total length. In 1996, shark researchers Michael D. Gottfried, Leonard Compagno, and S. Curtis Bowman proposed a linear relationship between the great white shark's total length and the height of the largest upper anterior tooth. The proposed relationship is: total length in meters = − (0.096) × [UA maximum height (mm)]-(0.22). Among several specimens found in the Gatún Formation of Panama, one upper lateral tooth was used by other researchers to obtain a total length estimate of using this method. In his 2015 book, The Story of Life in 25 Fossils: Tales of Intrepid Fossil Hunters and the Wonders of Evolution, Donald Prothero proposed the body mass estimates for different individuals of different length by extrapolating from a vertebral centra based on the dimensions of the great white, a methodology also used for the 2008 study which supports the maximum mass estimate. In 2019, Shimada revisited the size of megalodon and discouraged using non-anterior teeth for estimations, noting that the exact position of isolated non-anterior teeth is difficult to identify. Shimada provided maximum total length estimates using the largest anterior teeth available in museums. The tooth with the tallest crown height known to Shimada, NSM PV-19896, produced a total length estimate of . The tooth with the tallest total height, FMNH PF 11306, was reported at . However, Shimada remeasured the tooth and found it actually to measure . Using the total height tooth regression equation proposed by Gottfried and colleagues produced an estimate of . In addition, a megalodon jaw reconstruction developed by fossil hunter Vito Bertucci contains a tooth whose maximum height is reportedly over . Teeth and bite force |alt=A sideview of the inside of a megalodon jaw reconstruction showing five rows of teeth. Each row is more horizontal than the last, with the last row essentially resting on the jaw. 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). Megalodon teeth can measure over in slant height (diagonal length) and are the largest of any known shark species, implying it was the largest of all macropredatory sharks. The dental formula of megalodon is: . 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, In 2021, Antonio Ballell and Humberto Ferrón used Finite Element Analysis modeling to examine the stress distribution of three types of megalodon teeth and closely related mega-toothed species when exposed to anterior and lateral forces, the latter of which would be generated when a shark shakes its head to tear through flesh. The resulting simulations identified higher levels of stress in megalodon teeth under lateral force loads compared to its precursor species such as O. obliquus and O. angusteidens when tooth size was removed as a factor. This suggests that megalodon teeth were of a different functional significance than previously expected, challenging prior interpretations that megalodon's dental morphology was primarily driven by a dietary shift towards marine mammals. Instead, the authors proposed that it was a byproduct of an increase in body size caused by heterochronic selection. Internal anatomy Megalodon is represented in the fossil record by teeth, vertebral centra, and coprolites. 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. attributed to megalodon|alt=Smmothly rounded dark brown rock-like coprolite 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 . 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 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 of a whale bitten in half by a megalodon with visible gashes from teeth.|alt=A square piece of fossil bone with some roughly parallel grooves across it. with bite marks made by Megalodon 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. Additionally, nitrogen isotopes found that megalodon's trophic level was at least two levels higher than the great white shark. 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. In addition to this, they also targeted seals, sirenians, and sea turtles. Many whale bones have been found with deep gashes most likely made by their teeth. The feeding ecology of megalodon appears to have varied with age and between sites, like the modern great white shark. It is plausible that the adult megalodon population off the coast of Peru targeted primarily cetothere whales in length and other prey smaller than itself, rather than large whales in the same size class as themselves. Meanwhile, juveniles likely had a diet that consisted more of fish. Feeding strategies '' whales|alt=A painting of a megalodon about to eat two small whales. The mouth is open, and two rows of teeth are visible only on the bottom jaw. There are two other sharks in the background. 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. 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 '' from a probable nursery area in the Gatún Formation of Panama|alt=Several triangular fossil shark teeth on a white background. 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 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 per year, and a length of at birth. For a individualwhich they considered the maximum attainable sizethis 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 based on the 3D reconstruction which resulted in the complete vertebral column to be 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. the Bone Valley Formation of Florida and the Reverté Quarries of Spain. 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 at their smallest, sea turtles, dugongs, ==Paleoecology==

Range and habitat Megalodon had a cosmopolitan distribution. It most commonly occurred in subtropical to temperate latitudes. Competition from macroraptorial sperm whales, such as Livyatan (above). 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. Fossilized teeth of an undetermined species of such physeteroids from Lee Creek Mine, North Carolina, indicate it had a maximum body length of 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. 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. 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. Such diversity presented an ideal setting to support a super-predator such as megalodon. 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. and thus consistent with megalodon being mesothermic. 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, 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. Multiple compounding environmental and ecological factors including climate change and thermal limitations, collapse of prey populations and resource competition with white sharks are believed to have contributed to decline and extinction of megalodon. The extinction of megalodon set the stage for further changes in marine communities. The average body size of baleen whales increased significantly after its disappearance, although possibly due to other, climate-related, causes. Conversely the increase in baleen whale size may have contributed to the extinction of megalodon, as they may have preferred to go after smaller whales; bite marks on large whale species may have come from scavenging sharks. Megalodon may have simply become coextinct with smaller whale species, such as Piscobalaena nana. The extinction of megalodon had a positive impact on other apex predators of the time, such as the great white shark, in some cases spreading to regions where megalodon became absent. ==In popular culture==

to be around 11,000 to 24,000 years old.|alt=Painting of a three-masted ship sailing in the ocean 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 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. Megalodon is the official state shark of Maryland. Megalodon teeth are the state fossil of North Carolina. ==See also==