Megalodon, scientifically known as Otodus megalodon, meaning "big tooth," was an extinct species of giant mackerel shark that lived approximately 23 to 3.6 million years ago (Mya), from the Early Miocene to the Early Pliocene epochs. Regarded as one of the largest and most powerful predators to have ever lived, megalodon is only known from fragmentary remains, and its appearance and maximum size are uncertain. The fossil record indicates that it had a cosmopolitan distribution.
Physical Characteristics and Size Estimation
Scientists have proposed maximum body length estimates between 14.2 and 24.3 metres (47 and 80 ft) based on various analyses. The modal lengths for individuals of all ontogenetic stages from juveniles to adults are estimated at 10.5 meters (34 ft).
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. Another interpretation is that megalodon bore a similarity to the whale shark (Rhincodon typus) or the basking shark (Cetorhinus maximus). 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.
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. 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.
Traditional Views on Megalodon's Diet
Fossil evidence shows that the Megalodon primarily fed on large marine mammals including whales, dolphins, sea lions, dugongs (sea cows), as well as sea turtles and large fish. Fossil bones of these large marine mammals frequently bear bite marks and feeding damage that match Megalodon. Megalodon teeth have also been found in close association with skeletons of it’s prey. Based on comparisons of it’s body size and likely behavior, an adult Megalodon shark may have needed up to 2,500 lbs of food per day.
Read also: Learn how spa therapy can enhance your overall health.
Not only do fossil bones of whales often bear the scars of Megalodon feeding but Megalodon teeth very frequently show feeding damage. It’s not uncommon for it’s teeth to be found with sheered off tips and nicks to the blade that would have been caused when they hit bone. Like all sharks, the Megalodon rapidly replaced broken or worn teeth. It had 4 or 5 rows of teeth in it’s mouth which acted like a conveyer belt, replacing damaged or missing teeth within about 48 hours.
Hunting Strategies
One of the things Megalodon lacked was a refined, high-level strategy for attacking and killing its prey, but its attacks were effective, and that was what mattered. In some of the cetaceans that have been studied, compression damage is seen. That indicates a massive impact from below, and leads to the scenario that Megalodon would approach whales and other prey from below, so it would not be seen. That usually resulted in the prey ending up in the Megalodon’s jaws, but if that didn’t happen, the prey was too stunned from the hard impact to swim away. That gave Megalodon time to get in another bite, which generally killed his prey. A common area targeted by Megalodon was the rib cage. Because he had strong teeth and a lot of bite force, striking the rib cage meant a crushing blow that could damage the internal organs of its prey. That caused big injuries that the prey could not survive and gave Megalodon the best chance to get a meal. Some Megalodon fossils show teeth that have compression fractures. Those would probably not have happened if Megalodon had not been biting into bone when it attacked its prey. Of course, there were some animals that Megalodon went after that were just too big to bite into, such as large whales.
Isotopic Analysis and Dietary Versatility
A new study has uncovered surprising insights into the feeding habits of the largest predatory fish to ever roam the Earth's oceans, challenging long-standing assumptions about the prehistoric predator. For centuries, scientists believed that Otodus megalodon hunted exclusively at the top off the food chain, but a new study led by Jeremy McCormack from the Department of Geosciences at Goethe University Frankfurt found that its diet was far more flexible than previously thought.
By analyzing the levels of zinc in the fossils, the study found that while Megalodon did surely feast on whales and dolphins whenever it had a chance, the shark adjusted its diet based on availability of the prey. Zinc occurs in atomic variants (isotopes) of different weights, and is ingested with food. Less of the heavier isotope zinc-66 than the lighter isotope zinc-64 is stored in muscles and organs. Predatory fish absorb significantly less zinc-66 and those at the top of the food chain absorb even less.
"Since we don't know how the ratio of the two zinc isotopes at the bottom of the food pyramid was at that time, we compared the teeth of various prehistoric and extant shark species with each other and with other animal species. This enabled us to gain an impression of predator-prey relationships 18 million years ago," explained McCormack in a statement. Results of the study showed that the levels of zinc found in the Megalodon couldn't be sharply differentiated from the lower levels of the pyramid, suggesting that the largest shark that ever lived was flexible enough to feed on both marine mammals and large fish from the top of the food pyramid as well as lower levels.
Read also: Facial oil: Benefits and how to use
The shark's diet also greatly varied depending on its location and regional availability of prey. Fossils recovered from one German city showed more signs of the sharks preying on animals that were lower on the food chain compared to those found in a different part of the country. This is likely due to regional differences in food availability. In short, megalodon wasn’t just a whale-eater-it was an opportunistic predator that adapted to its surroundings.
Trophic Level Studies
A team of Princeton researchers has now discovered clear evidence that Megalodon and some of its ancestors were at the very highest rung of the prehistoric food chain - what scientists call the highest “trophic level.” Indeed, their trophic signature is so high that they must have eaten other predators and predators-of-predators in a complicated food web, say the researchers.
To reach their conclusions about the prehistoric marine food web, Kast, Sigman and their colleagues used a novel technique to measure the nitrogen isotopes in the sharks’ teeth. The nitrogen isotope levels in a creature’s cells reveal whether it is at the top, middle or bottom of a food chain. Organisms that eat them then incorporate that nitrogen into their own bodies, and critically, they preferentially excrete (sometimes via urine) more of nitrogen’s lighter isotope, N-14, than its heavier cousin, N-15. In other words, N-15 builds up, relative to N-14, as you climb up the food chain.
Megalodon's Extinction and Dietary Factors
As the shark preferred warmer waters, it is thought that oceanic cooling associated with the onset of the ice ages, coupled with the lowering of sea levels and resulting loss of suitable nursery areas, may have also contributed to its decline. A reduction in the diversity of baleen whales and a shift in their distribution toward polar regions may have reduced megalodon's primary food source. In fact, with both species eating generalist diets, great white sharks might have outcompeted megalodons for food and ultimately played a role in their demise.
Read also: The role of alpha-keto acids in metabolism.