Megalodon: insights into the largest prehistoric shark

This scene is the stuff of nightmares, but the reality is that it will never happen. This gigantic shark with fearsome jaws certainly was real, but it went extinct long before humans walked the earth. Megalodon dominated prehistoric seas until its disappearance about 3.6 million years ago, in a period of geological time known as the Miocene. Our own species has only been on earth for just over 300,000 years. The only reason we know megalodon even existed is because of its teeth, which are now prized fossils found on beaches and in ancient riverbeds and archaeological sites.

In fact, most of what we know (or think we know) about megalodon has been gleaned from its teeth. The second part of its scientific name, megalodon, quite literally translates as ‘large tooth’. For decades, scientists have analysed its fossil teeth from around the world to gain insights into everything from the meg’s body dimensions to its diet and reproductive habits. As technology advances, they are making new discoveries all the time (as well as debunking old ones!) and we are slowly building a picture of how this true ocean giant looked and lived…

How big was megalodon?

Not only was megalodon the largest species of predatory shark on earth, it was also one of the largest fish to have ever existed. Basing their estimates on the size of the animal’s teeth, scientists think that megalodon could have reached sizes of 18–20 metres (59–65 feet), but more likely averaged around 14 –15 metres (46–49 feet) in length. To put this in perspective, the largest recorded great white shark – currently our largest extant predatory shark – is six metres (20 feet) long! So megalodon was possibly almost double the size of the largest great white shark on record. If you’re still struggling to picture just how big that is, it’s roughly the same length as the average double-decker bus.

And giant adults mean giant babies! Scientists estimate that megalodon would have measured two metres (6.5 feet) long at birth – the largest neonate size of any shark. This has all been inferred from the fossilised teeth of juvenile megalodons.

Megalodon was also the last of the ‘megatooth’ lineage – a long line of large, predatory sharks that show a purported increase in size through time (in other words, they kept evolving to reach larger and larger sizes). Interestingly, scientists hypothesised that megalodon would have continued to grow larger as time went on, but recent studies have shown that it actually reached stasis, meaning that it remained at an average size throughout its existence. Researchers believe this may have been because of environmental constraints (it takes a lot of energy, and certain conditions, to be that large), natural selection or because the species was close to its ‘optimum’ size. Anything larger may not have been able to move as fast or as efficiently.

How do we know how big megalodon was?

Scientists can project how large megalodon was from the size of its teeth. The largest tooth on record was 18 centimetres (seven inches) tall. Tooth size has been found to be a good indicator of body size in extant predatory sharks, and larger teeth generally mean larger bodies. However, the body dimensions of megalodon can only be speculated – without a complete skeleton, it’s hard to say for certain.

Scientists have also used modern-day sharks as an analogue to model megalodon’s body dimensions. This study suggests that a 16-metre (52.5-foot) individual would have had a head 4.65 metres (15 feet) long, a dorsal fin 1.62 metres (5.25 feet) high and a caudal fin 3.83 metres (12.5 feet) high. However, the methodology has been questioned by other academics – megalodon research is constantly evolving, long after the species itself!

The most recent research looking into megalodon’s body dimensions used a rare, well-preserved fossil of part of an individual’s vertebral column (which, in itself is the size of a dinner plate) to produce a 3D model. The result suggests that megalodon could have reached a maximum length of 20 metres (65.5 feet) and had a whopping total body mass of 61,560 kilograms (60.5 tons). The model also suggests that megalodon would have had a slightly stocky body shape and long pectoral fins to allow for efficient movement.

How many teeth did megalodon have?

It’s thought that megalodon had up to 276 teeth at a time. Like other shark species, it probably would have lost and replaced teeth throughout its lifetime.

How many teeth did megalodon have in a lifetime?

Based on the figures from living sharks today, scientists estimate that it could have gone through as many as 40,000 teeth during the course of its life.

Are megalodon teeth common?

Megalodon teeth have been found on every continent except , although most have been discovered in Australia, Japan and the United States. As megalodon would have been continuously losing and replacing teeth, the sea floor would have been littered with them. Although not all of them would have fossilised, the sheer volume means that there are quite a few out there and in certain places you have a good chance of finding one. Areas that used to be submerged by ancient seas but are now dry land – like North Carolina and South Florida – are hotspots for finding megalodon teeth. There, avid megalodon tooth hunters search in the sediment and some strike it rich – a single tooth has been known to sell for US$2,600!

The teeth are also the most common fossil of megalodon to be found. All sharks have a skeleton made of cartilage, which is a softer tissue than the bones that you or I have; these are coated in calcium phosphate. Once a shark dies, much of that cartilage disintegrates – apart from pieces that are particularly thick or are preserved under special circumstances. Most of the time all that’s left behind are the robust teeth, which are easily fossilised. Only one reasonably well-preserved specimen of megalodon vertebrae (spinal column) has been found in the world.

How old are megalodon teeth?

This depends on when the fossil tooth was found. The earliest known tooth dates to about 20 million years ago and the youngest to 3–4 million years.

How sharp are megalodon teeth? What did megalodon teeth look like?

Megalodon’s teeth were designed for cutting and tearing. They are large in size (up to 18 centimetres, or seven inches, high), with fine serrations on the cutting edges (much like a knife). They also have a convex tooth ‘face’ and a darker, chevron-shaped section near the root, known as a bourlette.

Can megalodon teeth be small?

Yes! As a young megalodon grew, its teeth would have grown too, meaning that juvenile megalodon would have had much smaller teeth than the adults. In fact, collections of juvenile teeth at certain sites – like the Gatun Formation in Panama – suggest that megalodon had nursery grounds, just as many shark species alive today have. Juveniles would have probably taken refuge from predators in relatively shallow water. Although they were large pups, the ocean during the Miocene – when megalodon lived – would have been full of other equally gigantic predators on the hunt for an easy meal, including other prehistoric sharks. The Gatun Formation used to be a marine strait that connected the Pacific Ocean and Caribbean Sea in the late Miocene and it would have been quite a shallow environment perfect for juvenile megalodon.

What are megalodon teeth made of?

A shark tooth has a hard, mineral-rich outer casing known as enameloid (one of the hardest mineralised tissues produced by animals) and an inner core made of dentine.

What did megalodon eat?

Scientists have found evidence of megalodon’s eating habits from scars on prehistoric whale bones that match the pattern of a megalodon tooth. Some even have broken parts of megalodon teeth still embedded in them! It’s thought that, as well as large whales, megalodon would have eaten other large fish, including sharks. Very recent science indicates that megalodon occupied an extremely high trophic position – meaning it was at the very top of the food chain.

To bring down large and mobile prey like whales, megalodon would have had to be a fierce and efficient hunter. It could open its jaws to a width of 2–3 metres (6.5–10 feet) – wide enough to engulf two humans – and is predicted to have had a bite force (essentially, how hard an animal can close its mouth and the amount force it exerts while doing so) of between 108,514 and 182,201 Newtons. This makes it one of the most powerful vertebrate predators in history. If estimates are correct, megalodon had a bite force three times that of Tyrannosaurus rex and a whopping 10 times that of a great white shark!

Scientists have even used 3D models generated from a rare fossil of megalodon vertebrae to estimate how fast megalodon may have been. The results suggest that it was able to cruise at speeds faster than any other shark alive today! This would have allowed it to cover great distances, possibly between feeding grounds, and keep up with equally agile prey. According to the authors of the 3D modelling research, megalodon certainly earns the title of ‘transoceanic superpredator’.

When did megalodon exist?

Megalodon was roaming the ocean from the Miocene (a time period roughly between 23 and 5 million years ago) to the Pliocene (5.3–2.5 million years ago). The earliest known fossils date to 20 million years ago and it’s currently thought that megalodon went extinct around 3.6 million years ago.

Where would megalodon have lived?

It’s hard to tell this exactly, given that we only have its teeth to go by and the world has changed a lot since it prowled the seas – our land and water masses look completely different. But it appears that megalodon had a worldwide distribution and was a cosmopolitan species. It’s also thought that it lived in warm, tropical waters.

Concentrations of juvenile teeth at certain sites – like the Gatun Formation in Panama – suggest that megalodon had nursery grounds in shallow coastal waters, much like modern sharks.

What was the life span of megalodon?

It is thought that megalodon was very long-lived, perhaps living up to 88–100 years old.

How do we know how long megalodon lived?

It’s very hard to tell this, given the lack of evidence. Well-calcified vertebrae can be used to examine a shark’s age by counting the number of annual deposits, much like rings on a tree trunk. There are some issues with this method, but scientists have used the only well-preserved megalodon vertebrae in the world to estimate their age. And they have backed up their estimate with information from similar, modern-day sharks.

We also know megalodon existed for roughly 16 million years, before its extinction 3.6 million years ago.

Why did megalodon go extinct?

Megalodon was extinct by the end of the Pliocene, about 2.5 million years ago. Although it’s difficult to say exactly why it went extinct, one of the most popular theories is that oceanographic and climate changes led to its demise. We know that around this time global temperatures were falling. As the earth cooled, sea surface temperatures also began to drop, affecting the marine food web. Scientists believed this impacted large marine mammals as well as fish and other smaller organisms that could not cope with the colder temperatures.

This could have caused megalodon’s extinction in a few ways. Firstly, as the food chain began to collapse, megalodon’s prey may have become sparse or gone extinct itself, leaving megalodon without the food it needed to survive. Secondly, megalodon may have been physiologically limited to warmer waters, meaning that it could not adapt to cooler seas. And lastly, inshore nursery grounds could have been lost to ice and/or retreating seas.

What is the relationship between great white sharks and megalodon?

A fairly common theory was that great white sharks were directly descended from megalodon. Therefore megalodon used to be placed in the white shark genus Carcharodon. This is why so much of the imagery and reconstructions of megalodon imply that it simply looked like a huge version of a great white – and why scientists used to draw comparisons between the two to theorise about the meg’s behaviour.

However, as more fossils have been discovered and analysed, it seems that this theory is incorrect. Megalodon is actually the last member of a lineage entirely different from the great white’s – the megatooth sharks. It is now placed in the Otodus genus, within the order Lamniformes (the mackerel sharks), to which the great white also belongs. However, the great white’s ancestor is from a different lineage and may even have lived alongside megalodon – some scientists think they may have competed with each other, which could have contributed to megalodon’s extinction.

Could megalodon still exist?

Despite what you might see online and in the media – no, megalodon no longer exists, except in a museum. We know this for a number of reasons. Firstly, because sharks lose so many teeth in their lifetime, we’d soon find a recent megalodon tooth that could be reliably dated to the present day. Secondly, we’d definitely see evidence in the prey species, such as tooth marks on large whales. Thirdly, despite what some popular films might suggest, megalodon could not have survived in and is unlikely to be lurking in the depths out of sight. There is strong evidence to suggest that its preferred habitat was warmer coastal waters. Prey in the deep would be too scarce and the temperature well below the meg’s physiological limits. And lastly, such a large, active shark would be pretty hard to miss! If you think about all the species alive today with similar niches (warm temperate or tropical and relatively shallow waters) and how often we see them, it’s safe to assume there would be regular sightings of such a large shark. And with the number of people in the water diving, swimming and exploring, we’d definitely know if megalodon were still roaming the earth’s oceans.

We could be more clear here about their preferred habitat being warmer coastal waters and judging by how often we see smaller extant predatory sharks that have the same range, we would likely see megalodon a whole lot more often due to their size.

Want more? Head over to the Megalodon Fact File for more on this incredible prehistoric shark species.