Carcharocles

C. megalodon. Credit: Oliver Demuth.

*Carcharocles* is an extinct genus of "megatoothed" otodontid sharks that lived in the Americas, Asia, Africa, Europe and Australia from the Early Miocene to the Late Pliocene.

## History

Renaissance accounts place large triangular teeth embedded in rocky formations, called glossopetrae, and were believed to have been the petrified tongues of snakes and dragons. Nicholas Steno (1667) found they were shark teeth, producing paleoart of a shark head and teeth. They were described by Steno in The Head of a Shark Dissected, which also contained an illustrated megalodon tooth. Louis Agassiz (1843) named it *Carcharodon megalodon* from teeth. Edward Charlesworth (1837) moved it to *Carcharias*, but still cited Aggasiz (1843) as using the name before its actual descriptor date. Charles Davies Sherborn (1928) listed an 1835 series of articles authored by Agassiz as the first description of megalodon. The name translates to "big tooth" from the romanticized Ancient Greek μέγας and ὀδούς. An 1881 classification names it *Selache manzonii*. The first records of megalodon remains seem to appear in Mesoamerican, art, lore and archeology.

## Description

One interpretation of megalodon states it is similar to the whale shark and the basking shark, with a crescent-shaped tail fin, a smaller anal and dorsal fin and a caudal keel on the caudal peduncle. This is common for large marine animals, and is observed in whales, tuna and sharks. This reduces swimming drag. Head shape varies between species since most drag-reducing adaptations are to the posterior. It has teeth closely resembling the sand tiger, since *Carcharocles* derives from *Otodus*. It has been suggested it was built similar to the sand tiger, but this is unlikely, since the sand tiger is a carangiform swimmer, requiring faster movement than the thunniform movement seen in great whites. Megalodon is known from teeth, vertebral centra and coprolites. It is known from poor remains since its cartilaginous skeleton often fully decomposes before preservation. It's jaws were made shorter and blunter to fit an overall larger dentition. It is more developed than the great white shark. The chondrocranium is blockier and more robust.

The most notable vertebral column, and the only of megalodon, was found in the Antwerp Basin, Belgium in 1926. 150 vertebral centra were recovered, from 55-155 millimeters (2.2-6 inches) in diameter. However, their vertebra may have grown much larger, finding it likely had possibly over 200 centra, larger than most sharks, only rivalled by the great white shark. Another partially-preserved column was found from the Gram Formation, Denmark in 1983. 20 vertebral centra were found, from 100-230 millimeters (4-9 inches) in diameter. Coprolites recovered are spiral-shaped, indicating a spiral valve in the intestines, similar to Lamniformes. Miocene coprolites from Beaufort County, South Carolina are known, one being 14 centimeters (5.5 inches) long. Gottfried et al. reconstructed a megalodon skeleton, put on display at the Calvert Marine Museum and the Iziko South African Museum. It is 11.3 meters (37 feet) long, representing a mature male. It was based on ontogenetic changes. *C. auriculatus* is defined by coarse serrations on the edge and two large cusplets. Transitional specimens of this species and *C. angustidens* have a less curved root, finer serrations and defined recurved cusps; due to these small differences, some suggest that it be placed into *C. sokolovi*, although this is commonly synonymized. C. angustidens is known from some vertebrae, the most complete from 26 million year-old New Zealand with 165 teeth and 35 centra associated. This species is distinguished by a triangular crown with sharp, finely serrated cusps.

## Classification

It is beloieved by some that this genus can be placed into *Otodus* to avoid poly-/paraphyly, although these phylogenetic scenarios are hypothetical and are not informed by morphological data. Others argue that the subgenera, subspecies and species sometimes assigned to this genus can be adequately distinguished on the basis of serrations, leaving *O. obliquus* and all unrevised species in the original genus and all serrated forms to *Carcharocles*. As this genus is sometimes considered a subgenus of *Otodus*[*citation needed*], members of *Carcharocles* are sometimes arranged in subgeneric stages (which is not generally approved in vertebrate paleontology). *C. angustidens* was described by Agassiz (1835) as a member of *Carcharodon*, which was shifted to *Otodus* by Glikman (1964) who noticed ancestry with *O. obliquus*. Cappetta (1987) moved all related megatooths to *Carcharocles*, as this transition had become widespread and generally accepted. Agassiz (1843) assigned *C. chubutensis* to *Carcharodon*, which was moved by Glikman (1964) and Cappetta (1987). Gottfried and Fordyce (2001) controversially suggested that their specimen of *C. angustidens*, the best preserved, suggests close affinities with *Carcharodon* and that all chronospecific members be moved to that genus as such.

* *C. aksuaticus*.
* *C. auriculatus*.
* *C. angustidens*.
* *C. chubutensis*.
* *C. megalodon*.
1/5
Though the first megalodon occur in the Late Oligocene, it is still debated when the species really emerges, with dates as young as 16 million years ago. It went extinct 2.6 million years ago, with claims of younger teeth found unreliable. A 2019 assessment finds an extinction date of 3.6 million years ago. It is considered an otodontid inside *Carcharocles*; it was previously assigned *Carcharodon* due to dental morphology, but this was found to be convergent evolution, as megalodon has much finer serrations. Some argue these differences are too small and obscure to be taken into consideration. The genus *Carcharocles* is often considered synonymous with *Otodus*. Multiple theories using this species have been considered. *C. aksuaticus* is believed to be a transitional species between *Otodus obliquus* and *C. auriculatus*, only separated through derived species having serrated cusps and blade. This species is also sometimes placed in *Otodus*. Greenfield (2022) suggested that *Otodus poseidoni*, and by extension *O. p. poseidoni*, be synonymized with *C. auriculatus*.

## Paleobiology

The body temperature of megalodon was determined to have been higher than other sharks. As well, it had higher metabolic costs, which combined with the partial endothermy, may have made it at higher risk for extinction

### Diet

Megalodon were opportunistic feeders, with their speed, jaws and large feeding apparatus making it a capable apex predator that consumed dolphins, small whales, cetotheres, squalodontids, sperm whaled, bowhead whales, rorquals, seals, sirenians, fish, smaller sharks and sea turtles. It was among the most powerful of the apex predators. A calcium isotope study found it fed on a higher trophic level. Many whale fossils from megalodon localities bear deep gashes probably produced by megalodon teeth, with some excavations yielding teeth near chewed whale remains, sometimes being associated. Megalodons in offshore Peru preyed upon 2.5-7 meter (8.2-23 foot)-long cetotheres, with juveniles consuming more fish. The largest 18 meter (60 feet) estimate of megalodon likely meant that a mature adult would have to keep eating on a regular schedule to keep up with it's metabolism. Teeth from megalodon are often found discarded in fossil beds, as the cartilage that makes up the vast majority of shark skeletons easily rot, including megalodon. Because of this, the skeleton does not fossilize, leaving only teeth. Sometimes, megalodon teeth are found in fossils from other animals, such as one specimen preserving a shed megalodon tooth lodged into the bone on an indeterminate pinniped. Megalodon teeth are identified by their triangular shape, large size, robustness, fine serrations, a V-shaped neck and the lack of lateral denticles. The teeth meet with the jaw at a sharp angle, anchored by connective tissue fibers with roughness at the base indicating a mechanical advantage. The lingual side is convex, with the labial being slightly convex; flat. The anterior teeth sit near-perpendicular, with the posterior teeth slanted. They can measure 180 millimeters (7.1 inches)+ in slant height being the largest of any shark. In 1989, a near-complete dentition from Saitama, Japan was discovered. Another was found in the Yorktown Formation, which has been used to model a set of jaws at the National Museum of Natural History. In 1996, 2.1.7.43.0.8.4 was found to be the dental formula. The intermediate teeth appear to represent the A3. With over 250 teeth lining its jaws, megalodon had a very robust dentition. These spanned 5 rows. Large individuals may have had jaws 2 meters across. Its serrated teeth allowed for eased cutting of flesh and bone. It may have allowed for a 75° gape, but the USMN reconstruction shows a jaw gape of ~100°.

   S. Wroe et al. (2008) conducted experiments to find the bite force for megalodon and a great white shark. They found the former to have between 108,514-182,201 newtons (24,395-40,960 lbs). This is larger than *Carcharodon* and *Dunkleosteus* combined. They also note sharks shake their heads to amplify force, so it is likely these estimates are too low. Antonio Ballell and Humberto Ferrón (2021) use Finite Element Analysis to find stress distribution between 3 teeth forms between megalodon and other otodontids when used against anterior and lateral force. The latter would be formed if the shark thrashed its head while feeding. They found higher stress levels in megalodon than *O. obliquus* and C*. angustidens* when tooth size was excluded. This suggests megalodon teeth have a function previously ignored. This suggests its teeth evolved for reasons other than feeding on marine mammals. Instead, they found it was a product of increased size caused by heterochronic selection. One undescribed Miocene baleen whale provides insight for megalodon feeding, as it had targeted the heart and lungs, indicated by bites sustained to the ribcage. It was found attacks strategies may have depended on the prey size, since some cetotheres and small cetaceans show evidence of being forcefully rammed based on compression fractures, before being killed and consumed. There is also evidence of a strategy for raptorial sperm whales. One tooth of an indeterminate physeteroid closely resembling *Acrophyseter* from the Nutrien Aurora Phosphate Mine, North Carolina shows that megalodon or *C. chubutensis* had aimed for the whale's head to inflict a fatal bite, leaving distinct bite marks. These are more consistent with predation attempts, but scavenging can not be ruled out. Bites on the tooth roots show the whales jaw had been snapped during the bite, suggesting the aggressor had a powerful bite. This is the first antagonistic interaction between otodontids and sperm whales in the fossil record. Large cetaceans appeared during the Pliocene, where megalodon refined its hunting to adapt to this new diversification. Many flipper and caudal vertebrae of such whales bear megalodon bite marks, suggesting they would immobilize prey before consumption.

### Ontogeny

    In 2021, a study conducted by Kensu Shimada, co-authored by Matthew Bonnan, Martin Becker and Michael Griffiths, states that megalodon were born large. They used a CT scanner to peer inside the preserved fossils, revealing rows of growth bands similar to in trees. With this, they had revealed that the individual studied upon had died at 46, and was 9 meters (30 feet) long at death. By back-calculating when each marking was formed, they suggest sharks were born 6.6 feet (2 meters) long. Since megalodon birthed live, this would make them among the largest babies in the world. They speculate that babies grew in their mothers, and ate unhatched eggs as a way to fuel their enormous sizes at birth. A similar condition is seen in modern Lamniformes. Shimada notes that the embryos would have been costly for the mother to carry, this would have reduced rates of juveniles being eaten by predators. They also note that after birth, the juveniles would have grown at a steady 6.3 inches (16 centimeters) per year. Additionally, data says that individuals could have lived 100 years years, the average between 88 and 100. Megalodon lived a 'transient lifestyle', meaning that they lived short, but deadly lives. Mature megalodons likely lived in coastal waters, moving to offshore areas when they reached maturity. This life cycle may have been an annual occasion. Studies set on hundreds of juvenile megalodon individuals show that young lived in shallow waters.

    Reportedly, fossils of the massive fossil shark *Hemipristis serra* have been found at sites thought to have been megalodon nurseries, warmer shallow waters, where individuals gave birth. They may have picked off juveniles who were vulnerable. Evidence suggests that *Hemipristis serra* lived in the same oceans megalodon did, and lived in shallow areas. Because of this, it is very likely that the two were in competition . Megalodon nurseries are known from the Miocene of Panama, Spain, Florida and Maryland. Shark nurseries are shallow ecosystems filled with easy prey, which allows immature sharks to hunt and grow with ease, moving out into the ocean later in life. Similar sites have been noticed in *C. angustidens* (Oligocene of South Carolina), where 89% of teeth are juvenile, 3% are infant and 8% are adult. A 2021 study found these areas were dominated by juveniles, neonates and rarely, adults based on fossil teeth. Thus, the same may be true in *C. megalodon*.

### Distribution

Megalodon has a cosmopolitan distribution, found everywhere except for the northernmost part of the globe such as Canada, northern Europe, most of Russia and the poles. It is found most in temperate and subtropical latitudes, at northernmost 55°N with a temperature range of 24° Celsius (34-75° Fahrenheit). Arguably, it survived low temperatures due to mesothermy and conserved metabolic heat and body temperature. It lived in shallow and coastal waters, coastal upwellings, swampy coastal lagoons, sandy littorals and offshore deepwaters. It had a transient lifestyle. Adults did not live coastal, mostly living offshore. It may have migrated from coastal to oceanic environments based on the ontogenetic stage. Remains show larger individuals in the Southern Hemisphere, being larger in the Pacific rather than the Atlantic. These do not represent a changing size for latitude or a size trend over time, with the latter contrary to *Carcharocles*, of which megalodon may belong. Length distributions skews with larger individuals, showing a larger size may have gained ecological or competitive advantage. The northernmost occurrence of *C. megalodon* is on Spitsbergen in the Arctic Circle, occurring as southernmost as Cape Foulwind, New Zealand or Australia. Sources are unclear. *C. aksuaticus* is typically known from the Ypresian of Maryland, Virginia, Kazakhstan, Belgium and the United Kingdom. *C. auriculatus* is known from North and South Carolina, Morocco, Antarctica, the United Kingdom and Kazakhstan; transitional specimens are known from additional countries such as Egypt. *C. chubutensis* is known from Austria, Oman and North and South Carolina.

### Size

Great white sharks are among the most popular tool to estimate megalodon's size. Studies based on different shark populations suggest certain megalodon populations may have varied in sizes. One 2020 study finds, if estimated from *Lamna*, megalodon would have had a head 4.65 meters (15.3 feet) long, gill slits 1.41 meters (4 feet, 8 inches) tall, a dorsal fin 1.62 meters (5 feet, 4 inches) tall, pectoral fins 3.08 meters (10 feet, 1 inches) long pectoral fins and a tail fin 3.85 meters (12 feet, 8 inches) tall. A 2015 study found an average 18-kilometer/hour-swim-speed assuming a mass of 48 metric tons (53 short tons). This is typical for aquatic animals of this size. Megalodon may have grown large due to climate factors and an abundant amount of large prey. It may have also been influenced by regional endothermy, increasing metabolic rate and swim speed. Otodontids are considered ectothermic, including megalodon. However, the largest shark, the whale shark, is a filter feeder, with lamnids being regional ectotherms, which insinuates metabolic correlation with predation. These, alongside tooth oxygen isotopes and required higher burst swimming in macropredators, allow for otodontids to be regional ectotherms. In 2022, Shimada et al. published a study stating that megalodon grew larger in cooler water than those in warm water, based on measurements from teeth and shark nurseries, as predicted by Bergmann's rule. In the same study, they briefly mention 4 small teeth from Spain that were suggested to be from a dwarf population of megalodons that were 4 meters long. They theorize that they were produced through an enclosed environment, similar to insular dwarfs, though they would have lived in cooler waters. However, the evidence behind this is unstable and barely explained. *C. auriculatus* reached 4-9.5 meters (13-31 feet) long with a tooth length of 25-114 millimeters (0.98-4.49 inches); the erroneus *C. sokolovi* (=*auriculatus*), a chronospecies, is said to have reached 6 meters (20 feet). Some of the largest C. angustidens are 11-12 meters (36-39 feet) long; one medium sized specimen from New Zealand, 9.3 meters long, had teeth 9.87 centimeters (3.89 inches) in diagonal length and vertebral centra 1.1 centimeters (0.43 inches) in diameter. The smallest of individuals are 6-6.6 meters (20-22 feet) long. *C. chubutensis* was 13.5 meters (44 feet) at largest, with the average size for large individuals being 9-11 meters (30-36 feet) and smaller individuals at 4.6-6.3 meters (15-21 feet).

## Paleoecology

Megalodon lived in a very competitive paleoenvironment, being an apex predator that likely had a significant impact on environmental structuring. Megalodon correlates with the emergence and diversification of marine mammals such as cetaceans. Juveniles preferred environments where small cetaceans were abundant, with the adults preferring to be around large cetaceans; this may have developed shortly after their Oligocene appearance. It was contemporaneous with macroraptorial sperm whales and squalodontids, which were likely also apex predators, the most popular being *Livyatan*. It was probably a generalist rather than a specialist. Megalodon may have competitively excluded great whites, since fossil evidence suggests they avoided megalodon. When they do overlap, such as the Pliocene of Baja California, they probably inhabited the region at different times of the year when following their migrating prey. Megalodon likely cannibalized conspecifics. A cooling trend in the Oligocene led to glaciation at the poles, events that changed currents and precipitation, the stalling of the Gulf Stream that limited nutrient-rich waters from circulating, the largest sea level fluctuation in the Plio-Pleistocene and expanding glaciers are all events that occurred when megalodon lived, which may have influenced or led marine megafauna to extinction. Sea level drops in particular restricted many megalodon nurseries, areas that are required for a shark species to remain extant since they prevent juveniles from dying. Megalodon did not live  in cold waters, since it may not have been able to retain much metabolic heat. Their range significantly shrunk in the Pliocene due to cooling, but this is likely not a factor in their extinction. Distribution during the Miocene and Pliocene does not correlate with temperature trends, but abundance and distribution declined during the Pliocene. To some capacity, some occur in colder latitudes. It was likely mesothermic, as the global suitable habitat extent should not have been greatly affected by climate change.

Marine mammals were at their greatest diversity in the Miocene, which made an ideal setting to hold megalodon. However, many mysticetes had gone extinct by the end of the Miocene, with surviving species being faster and harder to catch. When the Central American Seaway closed, tropical whales decreased in both diversity and abundance. Megalodon likely went extinct based on the decline of small mysticetes, so it was probably dependent on these cetaceans. Marine megafauna in the Pliocene diminished 36% of large marine species, with 55% or marine mammals, 35% of seabirds, 9% of sharks and 43% of sea turtles. Extinction was selective for endotherms and mesotherms, but not poikilotherms; likely caused by a decreased food supply. This also points too megalodon being mesothermic. It may have been too large to adapt to changing food sources, maybe with cooling in the Pliocene forcing megalodon into the polar regions and declining whale populations there. Competition from sperm whales and killer whales may have also contributed to the disappearance of megalodon. During the Pliocene, whale-eating cetaceans emerge in high latitudes and in the tropics, adapting to colder water temperatures. When megalodon had gone extinct, baleen whales began to grow to massive sizes (possibly related also to climate). On the other hand, larger whales evolving may have led to the extinction of megalodon since they preferred smaller prey. Megalodon may have also gone coextinct with smaller whales. Apex predators thrived after megalodon disappeared, leading great whites to disperse into areas now lacking in megalodon. A 2019 study finds, based on teeth, it had went extinct 4-3.6 million years ago, before its prey had went extinct, due to climate change, great white competition and range fragmentation. *C. chubutensis* was behaviourally flexible to potentially occupy several environments, but it was likely an apex predator that preyed on fish, turtles, cetaceans and sirenids.

## Species

* *C. aksuaticus*
* *C. auriculatus*
* *C. angustidens*
* *C. chubutensis*
* *C. megalodon*

## Synonyms*C. giganteus* (=*C. megalodon*)

* *C. grosseserratus* (=*C. megalodon*)
* *C. incidens* (=*C. megalodon*)
* *C. macrodon* (=*C. megalodon*)
* *C. megalodon* (=*C. megalodon*)
* *C. mexicanus* (=*C. megalodon*)
* *C. polygurus* (=*C. megalodon*)
* *C. polygyrus* (=*C. megalodon*)
* *C. productus* (=*C. megalodon*)
* *C. (Prionodon) incidens* (=*C. megalodon*)
* *C. subauriculatus* (=*C. chubutensis*)
* *C. megalodon megalodon* (=*C. megalodon*)
* *C. productus* (=*C. megalodon*)
* *C. sokolovi* (=*C. auriculatus*)
* *C. arcuatus* (=*C. megalodon*)
* *C. branneri* (=*C. megalodon*)
* *C. brevis* (=*C. megalodon*)
* *C. costae* (=*C. megalodon*)
* *C. crassidens* (=*C. megalodon*)
* *C. crassirhadix* (=*C. megalodon*)
* *C. crassus* (=*C. megalodon*)
* *C. gibbesi* (=*C. megalodon*)
* *C. gigas* (=*C. megalodon*)
* *C. helveticus* (=*C. megalodon*)
* *C. humilis* (=*C. megalodon*)
* *C. intermedius* (=*C. megalodon*)
* *C. latissimus* (=*C. megalodon*)
* *C. leviathan* (=*C. megalodon*)
* *C. megalodon* (=*C. megalodon*)
	+ *C. m. indica* (=*C. megalodon*)
	+ *C. m. megalodon* (=*C. megalodon*)
	+ *C. m. polygyra* (=*C. megalodon*)
	+ *C. m. productus* (=*C. megalodon*)
	+ *C. m. siculus* (=*C. megalodon*)
	+ *C. m. yamanarii* (=*C. megalodon*)
* *C. morricei* (=*C. megalodon*)
* *C. polygurus* (=*C. megalodon*)
* *C. polygyrus* (=*C. megalodon*)
* *C. productus* (=*C. megalodon*)
* *C. quenstedti* (=*C. megalodon*)
* *C. rectidens* (=*C. megalodon*)
* *C. rectideus* (=*C. megalodon*)
* *C. semiserratus* (=*C. megalodon*)
* *C. subauriculatus* (=*C. chubutensis*)
* *C. tumidissimus* (=*C. megalodon*)
* *C. turicensis* (=*C. megalodon*)
* *M. arcuatus* (=*C. megalodon*)
* *M. auriculatus falciformis* (=*C. megalodon*)
* *M. branneri* (=*C. megalodon*)
* *M. brevis* (=*C. megalodon*)
* *M. crassidens* (=*C. megalodon*)
* *M. crassirhadix* (=*C. megalodon*)
* *M. crassus* (=*C. megalodon*)
* *M. gigas* (=*C. megalodon*)
* *M. heterodon* (=*C. megalodon*)
* *M. humilis* (=*C. megalodon*)
* *M. incidens* (=*C. megalodon*)
* *M. leviathan* (=*C. megalodon*)
* *M. megalodon* (=*C. megalodon*)
	+ *M. m. indicus* (=*C. megalodon*)
* *M. polygyrus* (=*C. megalodon*)
* *M. productus* (=*C. megalodon*)
* *M. rectidens* (=*C. megalodon*)
* *M. semiserratus* (=*C. megalodon*)
* *M. subauriculatus* (=*C. chubutensis*)
* *P. megalodon* (=*C. megalodon*)
* *P. m. megalodon* (=*C. megalodon*)
* *O. (Megaselachus) megalodon* (=*C. megalodon*)
* *O. megalodon* (=*C. megalodon*)
* *O. sokolovi* (=*C. auriculatus*)
* *O. subauriculatus* (=*C. chubutensis*)
* *O. poseidoni* (=*C. auriculatus*)
	+ *O. p. poseidoni* (=*C. auriculatus*)
* *"O." crassus* (=*C. auriculatus*)
* *S. manzonii* (=*C. megalodon*)

## Notable Specimens

* IRSNB P809: 34 teeth and 50 vertebrae from the Early Eocene Brussels Formation, belonging to *C. angustidens*.
* IRSNB P 928-9: 134 teeth; 93 vertebrae (8) and 97 teeth, 77 vertebrae (9) from the Early Oligocene Broom Clay Formation, belonging to *C. angustidens*.
* OU 22261: ~165 teeth and 32 vetebrae from the Late Oligocene Otekaike Limestone Formation, belonging to *C. angustidens*.
* NVM P253864: 33 teeth and a vertebrae from the Late Oligocene Jan Juc Formation, belonging to *C. angustidens*.
* HU 21771: 4 vertebrae from the Middle Eocene of Israel, belonging to *C. angustidens*.
* GMNH-PV 3246: 30 teeth and parts of the mandible of the Middle/Late Miocene Haraichi Formation, belonging to *C. megalodon*.
* INM-4-012886 - 932: 54 teeth and 4 vertebrae from the Early Miocene Kokozura Formation, belonging to *C. megalodon*.
* IRSNB P9893 (prev. IRSNB 3121): Around 150 vertebrae from the Middle/Late Miocene of Belgium, belonging to *C. megalodon*.
* NHMD 157890: Around 20 vertebrae from the late Miocene Gram Formation, belonging to *C. megalodon*. NHMT-V501: 12 vertebrae from the Early Miocene Towata/Matsuba Formation, belonging to *C. megalodon*.
* MGUH coll.: Around 30 vertebrae from the Late Miocene Gram Formation, belonging to *C. megalodon*.
* USNM 474994-474999: 6 isolated elements (rostral nodes?) from the Early Pliocene Yorktown Formation, either belonging to *C. megalodon* or *Parotodus benedenii*.
* UF 287616: A rostral nodes from the Early Pliocene Peace River Formation, either belonging to *C. megalodon* or *Parotodus benedenii*.

## References

1. ↑ https://palaeo-electronica.org/content/2021/3284-estimating-lamniform-body-size
2. ↑ https://www.nature.com/articles/s41598-020-80323-z
3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 https://en.wikipedia.org/wiki/Megalodon
4. ↑ https://www.cambridge.org/core/services/aop-cambridge-core/content/view/2060934F3D8F5089C22227213F0CB95A/S0003598X16002180a.pdf/div-class-title-sharks-in-the-jungle-real-and-imagined-sea-monsters-of-the-maya-div.pdf
5. ↑ 5.0 5.1 5.2 https://en.wikipedia.org/wiki/Otodus\_auriculatus
6. ↑ 6.0 6.1 6.2 https://en.wikipedia.org/wiki/Otodus\_sokolovi
7. ↑ https://palaeo-electronica.org/content/2021/3372-oligocene-shark-nursery
8. ↑ 8.0 8.1 8.2 8.3 https://en.wikipedia.org/wiki/Otodus\_angustidens
9. ↑ 9.0 9.1 https://palaeo-electronica.org/content/2021/3372-oligocene-shark-nursery
10. ↑ 10.0 10.1 10.2 10.3 https://en.wikipedia.org/wiki/Otodus\_chubutensis
11. ↑ 11.0 11.1 https://en.wikipedia.org/wiki/Otodus\_aksuaticus
12. ↑ 12.0 12.1 https://peerj.com/articles/625/
13. ↑ https://www.researchgate.net/profile/Tyler-Greenfield/publication/365652670\_Additions\_to\_List\_of\_skeletal\_material\_from\_megatooth\_sharks\_with\_a\_response\_to\_Shimada\_2022/links/637d00631766b34c5447b7fd/Additions-to-List-of-skeletal-material-from-megatooth-sharks-with-a-response-to-Shimada-2022.pdf
14. ↑ https://www.pnas.org/doi/10.1073/pnas.2218153120
https://twitter.com/FossilLocator/status/1329775955074805761
16. ↑ https://phys.org/news/2021-01-megalodons-gave-birth-large-newborns.html
17. ↑ https://www.fossilera.com/pages/megalodon-shark-nursery-found-in-panama
18. ↑ https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0010552
19. ↑ https://www.biodiversitylibrary.org/item/148185#page/437/mode/1up
20. ↑ https://www.tandfonline.com/doi/abs/10.1080/00288306.1972.10421956
21. ↑ https://www.gbif.org/species/144096597
22. ↑ https://paleobiodb.org/classic/basicTaxonInfo?taxon\_no=97249
23. ↑ https://www.tandfonline.com/doi/full/10.1080/08912963.2022.2032024
24. ↑ 24.00 24.01 24.02 24.03 24.04 24.05 24.06 24.07 24.08 24.09 24.10 24.11 https://usercontent.one/wp/pecescriollos.de/wp-content/uploads/2022/06/PI-04-Greenfield-2022-List-of-skeletal-material-from-megatooth-sharks.pdf
25. ↑ 25.00 25.01 25.02 25.03 25.04 25.05 25.06 25.07 25.08 25.09 25.10 25.11 https://incertaesedisblog.wordpress.com/2021/01/15/megatooth-shark-skeletal-specimens/