Carcharodon megalodon is an extinct species of shark that lived during the Cenozoic era. This species is thought to be one of the largest and most powerful predators in history. Fossils records suggest that Carcharodon megalodon was cosmopolitan in distribution, but was often found at subtropical and temperate latitudes. It mostly preyed upon cetaceans, large whales, pinnipeds, and porpoises. Carcharodon megalodon eventually died out when it became too large to sustain itself on the available food.
The fossils of Carcharodon megalodon have been excavated from many parts of the world, including Europe, North America, South America, Puerto Rico, Cuba, Jamaica, Australia, New Zealand, Japan, Africa, Malta, Grenadines, and India. Carcharodon megalodon teeth have also been excavated from regions far away from continental lands (e.g., the Mariana Trench in the Pacific).
Due to fragmentary remains, estimating the size of Carcharodon megalodon has been challenging. However, the scientific community acknowledges that Carcharodon megalodon was larger than the whale shark, Rhincodon typus. Scientists have focused their research upon two aspects of size: (1) total length (TL), and (2) body mass (BM).
In the 1990s, marine biologists (e.g., Patrick J. Schembri, and Staphon Papson) opined that C. megalodon may have approached a maximum of around 24 to 25 metres (79 to 82 ft) in total length (TL). The early total length (TL) estimation of Carcharodon megalodon is perhaps not far-fetched. However, Gottfried and colleagues (1996) proposed that Carcharodon megalodon could likely approach a maximum of 20.3 metres (67 ft) in total length (TL). Currently most experts agree this giant shark reached a total length (TL) of more than 16 metres (52 ft).
The first attempt to reconstruct the jaw of this shark was made by Professor Bashford Dean in 1909. From the dimensions of this jaw reconstruction, it was hypothesized that Carcharodon megalodon could have approached 30 metres (98 ft) in total length (TL), but in light of new fossil discoveries and advances in vertebrate sciences this jaw reconstruction is now considered to be inaccurate. Major reasons cited for this inaccuracy are (1) relatively poor knowledge of Carcharodon megalodon's dentition in Dean's time, and (2) inaccurate muscle structures. Experts suggest that a rectified version of Carcharodon megalodon's jaw model by Bashford Dean would be about seventy percent (70%) of its original size and would lead to a shark size consistent with modern findings. To resolve such errors, scientists, aided by new fossil discoveries of Carcharodon megalodon and improved knowledge of its closest living analogue's anatomy, introduced more quantitative methods for estimating its size based on the statistical relationships between the tooth sizes and body lengths in the great white shark.
Sharks, especially large species, are highly mobile organisms with a complex life history and wide distribution. Fossil records of Carcharodon megalodon indicate that it was cosmopolitan, and commonly occurred in subtropical to temperate latitudes. Prior to the formation of the Isthmus of Panama, the seas were relatively warmer. This would have made it possible for the species to live in all the oceans of the world.
Carcharodon megalodon had enough behavioral flexibility to inhabit wide range of marine environments (i.e. coastal shallow waters, coastal upwelling, swampy coastal lagoons, sandy littorals, and offshore deep water environments), and exhibited a transient life-style. Adult Carcharodon megalodon were not abundant in shallow water environments, and mostly lurked offshore. Carcharodon megalodon may have moved between coastal and oceanic waters, particularly in different stages in its life cycle.
Life History and Behavior
Sharks are generally opportunistic predators. However, scientists propose that Carcharodon megalodon was "arguably the most formidable carnivore ever to have existed."Its great size, high-speed swimming capability, and powerful jaws coupled with formidable killing apparatus, made it a super-predator with the capability to consume a broad spectrum of fauna.
Fossil evidence indicates that Carcharodon megalodon preyed upon cetaceans (i.e., dolphins, small whales, (including cetotherrids,squalodontids, and Odobenocetops), and large whales, (including sperm whales, bowhead whales, and rorquals), pinnipeds, porpoises, sirenians, and giant sea turtles.
Marine mammals were regular prey targets for Carcharodon megalodon. Many whale bones have been found with clear signs of large bite marks (deep gashes) made by teeth that match those of Carcharodon megalodon, and various excavations have revealed Carcharodon megalodon teeth lying close to the chewed remains of whales, and sometimes in direct association with them. Fossil evidence of interactions between Carcharodon megalodon and pinnipeds also exist. In one interesting observation, a 127 millimetres (5.0 in) Carcharodon megalodon tooth was found lying very close to a bitten earbone of a sea lion.
Carcharodon megalodon faced a highly competitive environment during its time of existence. However, Carcharodon megalodon, being at the top of the food chain, likely had a profound impact on the structuring of marine communities. Fossil evidence indicates a correlation between the emergence of Carcharodon megalodon and extensive diversification of cetaceans around the world. Juvenile Carcharodon megalodon preferred regions where small cetaceans were abundant, and adult Carcharodon megalodon preferred regions where large cetaceans were abundant. Such preferences may have developed shortly after they appeared in the Oligocene. In addition, Carcharodon megalodon was contemporaneous with macro-predatory odontocetes (particularly raptorial sperm whales and squalodontids), which were also likely among the apex predators of that time, and provided competition. In response to competition from giant macro-predatory sharks, macro-predatory odontocetes may have evolved some defensive adaptations; some species became pack predators, and some species attained gigantic sizes, such as Livyatan melvillei. By the end of the Miocene, raptorial sperm whales vanished from the fossil record and left an ecological void.
Like other sharks, Carcharodon megalodon also would have been piscivorous. Fossil evidence indicates that other notable species of macro-predatory sharks (e.g. great white sharks) responded to competitive pressure from Carcharodon megalodon by avoiding regions it inhabited. Carcharodon megalodon likely also had a tendency for cannibalism.
Sharks often employ complex hunting strategies to engage large prey animals. Some paleontologists suggest that the hunting strategies of the great white shark may offer clues as to how Carcharodon megalodon might have hunted its unusually large prey (i.e., whales). However, fossil evidence suggests that Carcharodon megalodon employed more effective hunting strategies against large prey than those of the great white shark.
Paleontologists have conducted a survey of fossils to determine attacking patterns of Carcharodon megalodon on prey. One particular specimen — the remains of a 9 metres (30 ft) long prehistoric baleen whale (of an unknown Miocene taxon) — provided the first opportunity to quantitatively analyze the attacking behavior of Carcharodon megalodon. The predator primarily focused its attack on the tough bony portions (i.e. shoulders, flippers, rib cage, and upper spine) of the prey, which great white sharks generally avoid. Dr. Bretton Kent elaborated that Carcharodon megalodon attempted to crush the bones and damage delicate organs (i.e. heart, and lungs) harbored within the rib cage of the prey. Such an attack would have immobilized the prey, which would have died quickly due to injuries to these vital organs. These findings also clarify why the ancient shark needed more robust dentition than that of great white sharks. Furthermore, the attack patterns could differ for prey of different sizes. Fossil remains of some small cetaceans (e.g. cetotheriids) suggest that they were rammed with great force from below before being killed and eaten.
During the Pliocene, larger and and more advanced cetaceans appeared. Carcharodon megalodon apparently further refined its hunting strategies to cope with these large whales. Numerous fossilized flipper bones (i.e., segments of the pectoral fins), and caudal vertebrae of large whales from the Pliocene have been found with bite marks that were caused by attacks of Carcharodon megalodon. This paleontological evidence suggests that Carcharodon megalodon would attempt to immobilize a large whale by ripping apart or biting off its propulsive structures before killing and feeding on it.
Fossil evidence suggests that the preferred nursery sites of Carcharodon megalodon were warm water coastal environments, where potential threats were minor and food sources plentiful. Nursery sites have been identified in the Gatun Formation of Panama, the Calvert Formation of Maryland, and the Bone Valley Formation of Florida. As is the case with most sharks, Carcharodon megalodon also gave birth to live young. The size of neonate Carcharodon megalodon teeth indicate that Carcharodon megalodon pups were around 2 to 4 metres (7 to 13 ft) in total length (TL) at birth. Their dietary preferences display an ontogenetic shift. Young Carcharodon megalodon commonly preyed on fish, giant sea turtles, dugongs, and small cetaceans; mature Carcharodon megalodon moved to off-shore cetacean high-use areas and consumed large cetaceans.
However, there is an exceptional case which suggests that juvenile Carcharodon megalodon may occasionally have attacked much larger balaenopterid whales. Three tooth marks apparently from a 4-7 m long Pliocene macro-predatory shark were found on a rib from an ancestral great blue or humpback whale that showed evidence of subsequent healing. Scientists suspect that this shark was a juvenile Carcharodon megalodon.
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