One megalodon's backbone alone was 11 metres long

The Belgian backbone is the best evidence of what a megalodon's body was like. Researchers worked out the shark's length from it in 1996, 2022 and 2025, and got different answers, because each assumed a different shape for the rest of the body.

The shape matters more than it seems. At almost the same length, the 2022 shark weighs 62 tonnes and the 2025 one about 30. For comparison, a blue whale 17 metres long weighs 37 tonnes.

What nobody knows. No megalodon has been found with its head, jaws or fins. Every drawing of one, the slender one included, is a calculation based on other sharks, living and fossil. The authors of the 2025 study call their own result “hypothetical”: the same backbone with other proportions would give a shorter or a much longer shark.

The estimate comes from the largest of about 20 vertebrae from the same shark, dug out of a clay pit at Gram, in Denmark, in 1978. It is 23 centimetres across, the largest shark vertebra known.

It is 1.484 times as wide as the widest Belgian vertebra. If the Danish shark had the same proportions, it was 24.3 metres long and weighed about 94 tonnes. The authors say the calculation is hypothetical and that a shark this size was a rare exception.

In 1989, during a move from one store to another, the vertebrae were badly damaged and thought lost. Some of the surviving pieces were identified only in 2017, in the collection of the Natural History Museum of Denmark. In 2026 researchers confirmed that the largest really was 23 centimetres across.

Between 1996 and 2025, studies gave megalodon lengths from 9 to 24 metres. The differences come from what they measured and from the living shark they compared it with.

The tooth-based figures start from the great white: they assume the ratio of tooth size to body length was the same in megalodon and the great white. Newer studies consider the resulting lengths too small, because megalodon was longer for its teeth.

The much-repeated 18 metres comes from older tooth-based maximums worked out with the great white. Newer studies question that method. Nor is the length of an ordinary adult known: the only study showing how common each size was uses estimates from teeth, made with the older method.

A shark replaces its teeth all its life. In 1667 Nicolaus Steno counted more than 200 teeth in the mouth of a single shark and wrote that new ones grew every day. Teeth are hard and fossilise easily, while a cartilage skeleton rarely survives. That is why fossil teeth are everywhere and skeletons almost absent.

The name is Greek for “big tooth”. It was given by the Swiss naturalist Louis Agassiz, in his volumes on fossil fish published between 1833 and 1843. He noted that no living shark has teeth even half as big.

Long before that, people found the teeth in rocks and called them “tongue stones”. Pliny the Elder believed they fell from the sky. In the early 17th century Fabio Colonna argued that they were sharks' teeth, and in 1667 Steno compared one with the teeth of a shark caught off the coast of Tuscany: they were alike “as one egg to another”.

Teeth and a few bitten bones reveal a surprising amount about its life.

A computer model from 2022, using a great white's body, estimated that a 5-metre whale could be eaten in three bites. The model assumes a bigger mouth than later studies allow, so the number is at best a rough guide.

What nobody knows. Whether pups grew up in “nurseries”, warm shallow bays, is still disputed. The teams that found many small teeth in Panama and Spain say yes; the team that recalculated the pups' size in 2025 thinks such large newborns needed less protection, which makes nurseries less likely.

About 14–15 million years ago a warm sea dotted with islands covered much of Transylvania and the Banat hills. The water may have been warmer than 21 °C. Megalodons reached this sea too: Romanian museums hold fewer than ten megalodon teeth.

In 2016 two teeth were described and photographed for the first time, from Lăpugiu de Sus, in Hunedoara county, and Borzești, in Cluj county. The Borzești tooth had been found in 1987 by a geology student and sat unpublished in a university drawer in Cluj for almost 30 years. Of the known teeth, only the Lăpugiu de Sus one, found in a stream, was collected this century.

In 2017 three old teeth from the museum in Aiud were added, from Cetea, Gârbova de Sus and Lopadea Veche, and in 2024 a tooth from Coșteiu de Sus, probably picked up in the 19th or early 20th century and kept ever since at the Natural History Museum in Vienna. Hungarian geologists had mentioned the species in Transylvania as early as 1896, but without describing a single tooth.

Judging by the size of the teeth, the authors of the 2016 study estimate the sharks at 8–10 metres: large youngsters or adults. In 2017 Nicolae Trif and Vlad Codrea noted that almost no bones of sea mammals have turned up in these rocks, so the big sharks may only have been passing through this sea.

The sea left something else behind. As it evaporated, it laid down the salt of the mines at Turda, Praid and Ocna Sibiului. The salt layers are a little younger than the beds with the teeth. The salt shows the sea was there; it says nothing about the sharks.

What nobody knows. The Romanian teeth are few and isolated, and the sharks' sizes come from a method dating from 2003 that, according to newer studies, gives values that are too small. Nobody knows how often megalodons passed through the sea here, or whether they raised their young in it.

Some teeth dredged from the seabed looked young, a few tens of thousands of years old. That date gave the age of the manganese crust that grew on an old tooth while it lay in the water, not the age of the tooth.

Nor is the deep ocean a likely hiding place. Megalodon lived in warm and temperate seas, and young ones' teeth have been found in shallow coastal water. And below 3,000 metres sharks of any kind are practically absent from every ocean.

In 2013 a TV channel broadcast a film with actors playing scientists hunting a living megalodon. Researchers protested: no evidence suggests it still exists.

Why it died out

Nobody knows for sure. Studies suggest several possible causes, without being able to say which mattered most: its range was already shrinking, the small whales it fed on were declining, the great white appeared and hunted similar prey, and a warm body needed a lot of food.

Eight statements about megalodon. Some are stories repeated everywhere.