For over 20 million years, a gigantic shark popularly known as megalodon stalked the world’s oceans—and this month, it will invade movie theaters in The Meg. Here are 15 facts about the toothy predator.

1. MEGALODON ISN'T THE SHARK’S FULL NAME.

It might be the moniker it goes by in pop culture, cable mockumentaries, and B-movies, but megalodon is only one half of this shark's scientific name. Most paleontologists classify the prehistoric predator under the extinct genus Carcharocles (or, more rarely, Otodus), while others think it belongs to the genus Carcharodon (whose only living member is the great white), making its scientific name either Carcharocles megalodon or Carcharodon megalodon. In either case, megalodon is not a genus name, but a species name (it’s like the difference between Homo and sapiens).

But there’s also a group of fossil bivalves—small, hard-shelled mollusks that emerged in the Devonian period and died out during the Jurassic—whose genus name is Megalodon (with a capital M). Don’t count on seeing them in any big-budget horror flicks.

2. SOME MEGALODON TEETH WERE OVER 7 INCHES LONG.

Because shark skeletons are made of cartilage—which doesn’t fossilize easily—our understanding of megalodon comes mainly from its teeth. Like sharks today, megalodon was constantly shedding its pearly whites, and its fossilized teeth have been discovered on every continent except Antarctica. Analysis of those chompers allowed scientists to determine that the species lived from 23 to 2.6 million years ago and was truly massive: The biggest megalodon tooth on record is 7.5 inches long. A great white's teeth reach a maximum length of about 3 inches.

3. MEGALODON HELPED INVENT MODERN GEOLOGY.

For centuries, people dug strange objects out of rocks in Malta that became known as glossopetrae, or tongue stones. Pliny the Elder felt glossopetrae fell from the heavens during an eclipse, and Medieval legend attributed them to Saint Paul casting a curse on the island’s serpents. Nowadays, it’s generally agreed that the largest glossopetrae were megalodon teeth.

In 1666, Nicholas Steno, a physician at the Florence court, was given the head of a shark to dissect, and he noticed the similarities between the shark’s teeth and glossopetrae. Although others were doing similar work before Steno, he became interested in how the teeth got into the rocks, and that led to more general work in geologic theory and how layers of rock form. Today, Steno is referred to as the “Father of Stratigraphy.”

4. WE'VE FOUND THEIR BACKBONES ...

They're much rarer than teeth, but occasionally, megalodon backbones are found—most often the central part of the vertebra known as the vertebral centra. In the 1860s, a fossilized spinal column with roughly 150 vertebrae was unearthed in Belgium. Japan and North America have yielded megalodon backbones as well.

5. ... AND THEIR POOP.

Another thing that the giant fish apparently left behind is petrified poop. At a deposit in South Carolina, hundreds of megalodon teeth were found near what’s been identified as the coprolites (a.k.a. fossil feces) of a large-bodied shark. Scientists aren’t sure, but the maker of this poop was probably a megalodon. The biggest recovered turd at the site was 5.5 inches long and spiral-shaped. Great white shark poop has a similar appearance because their lower intestines are twisted into a corkscrew-like configuration.

6. IT’S THOUGHT TO BE THE BIGGEST SHARK THAT EVER LIVED ...

Everyone wants to know how big it was—including the scientific community—but for now, all we can do is estimate. A complete megalodon skeleton has yet to be found, and it’s doubtful that one will ever turn up. Trying to make an educated guess about an extinct critter’s maximum size on the basis of scattered teeth, disembodied spinal columns, and the occasional turd is a daunting challenge.

Ichthyologist John E. Randall once compared the enamel heights of great white shark and megalodon teeth, and calculated that if megalodon had the same general body proportions as living great whites do, the prehistoric fish would be roughly 43 feet long. Using a different formula, biologist Michael Gottfried and some of his colleagues concluded that megalodon reached lengths of 52 feet and could have weighed 48 tons. They published their findings in 1996, six years before scientist Clifford Jeremiah used the width of megalodon tooth roots to calculate that a full-grown megalodon could be up to 54 feet long. Other estimates put the shark’s total size in the range of 67 to 82 feet.

The biggest species alive today is the peaceful whale shark, which can grow to be 40 feet long (while reports of longer specimens exist, they’re generally viewed as unreliable). Even the smallest estimates hold that megalodon was longer, and probably a lot heavier, so it's generally considered the largest shark—and most likely the biggest fish—of all time.

7 ... BUT IT WASN'T THE ONLY GIANT SHARK IN TOWN.

When one thinks “prehistoric giant shark,” the mental list includes megalodon and … no other animal. But while they were the biggest, some estimate that there could have been anywhere from 10 to 60 “Megatooth” sharks around the same time [PDF]. For instance, Carcharocles chubutensis (sometimes called C. subauriculatus) is reported as having teeth over 5 inches long—which means the shark would have been well in excess of 20 feet. Sadly, there’s much disagreement about who belongs where in the world of giant sharks, as many of these fossils are rare [PDF].

8. MEGALODON WAS A WHALE-EATER.

We know this because there are fossilized whale bones covered in scars that perfectly match the size and serrations of megalodon teeth. Just last year, the list of nibbled-on remains got longer. A study published in March 2017 announced that megalodon bite marks had just been documented on several fossilized bones from filter-feeding whales, which were unearthed in southern Peru and are about 7 million years old. “The bitten material,” wrote the paper’s authors, “includes skull remains referred to small-sized baleen whales” along with fragments of other bones from assorted whales and pinnipeds.

One of the victimized species was Piscobalaena nana, which looked like a miniature humpback; it measured just 16 feet long from nose to tail. Diminutive baleen whales such as Piscobalaena were quite common in the tropical waters megalodon once patrolled. It’s been suggested that megalodon might have specialized in eating the dwarf whales—which could help explain the great shark’s disappearance. As Earth grew cooler, small filter-feeding whales like Piscobalaena were replaced by giants like contemporary humpback and blue whales. Although these big mammals are built to survive in very cold water, it’s unclear if megalodon could. Robbed of its favorite prey and unable to pursue newer, bigger cetaceans, megalodon may well have been doomed. Or at least, that might be part of the story …

9. MEGALODON PROBABLY HAD A STRONGER BITE THAN T. REX.

In addition to whales and pinnipeds, megalodon's natural diet included fish, turtles, and distant early relatives of the manatee. Megalodon must have had a powerful bite to make short work of its prey. To figure out how strong its jaws were, a research group led by biologist Stephen Wroe CT scanned a 530-pound great white shark [PDF] and used that data to build a computer model of the fish’s head. After running the model through a few simulations, the scientists reported that a live great white can close its jaws with 4000 pounds of force, which led them to estimate megalodon's maximum bite force at 24,000 to 40,000 pounds. “At [40,000 pounds of force], I reckon it could have crushed a small car,” Wroe says. “Of course, it would probably have broken most of its teeth in the exercise.” If his conclusions are correct, megalodon had the strongest bite of any studied animal in history, including the Tyrannosaurus rex: According to one study from 2017, the dino exerted just 8000 pounds of force while clamping down on prehistoric prey.

10. ITS RELATIONSHIP WITH THE GREAT WHITE ISN'T CLEAR-CUT.

C. megalodon and the great white shark (Carcharodon carcharias) had many things in common. They both preyed on big marine mammals and their mouths were packed with broad, triangular teeth (although the great white’s aren't as finely serrated as megalodon’s). Given the similarities, biologists used to think the two sharks were close relatives and that megalodon was the great white’s direct ancestor. This is no longer the consensus. A 2005 comparison of several hundred shark teeth argued that the great white must have evolved from a type of extinct mako. Further support for this idea came in 2012, when paleontologists examined a set of fossilized jaws belonging to Carcharodon hubbelli, a prehistoric shark that lived 6.5 million years ago that exhibited intermediate features between broad-toothed makos and great whites. The fish’s teeth looked distinctly great white-esque—right down to the serrations. Although the exact relationship between megalodon and great whites is still up for debate, the prevailing view today is that the latter evolved from some type of mako.

11. ONE OF ITS POTENTIAL RIVALS WAS A MONSTROUS SPERM WHALE.

Livyatan melvillei was a type of sperm whale named after an Old Testament sea beast and Moby-Dick author Herman Melville. The creature was 45 to 60 feet long, making it comparable in size to its living brethren. But whereas modern sperm whales have relatively small teeth, Livyatan packed a mouthful of humongous teeth—the largest was 5 inches wide and 14 inches long, almost as big as a two-liter soda bottle. What on earth was this monster eating? Probably those dwarf baleen whales we mentioned earlier. Livyatan first appeared between 12 and 13 million years ago and its remains have been found in some of the same deposits as megalodon teeth. Paleontologists are researching the relation between the two, but they likely ate similar prey.

12. IT LOOKS LIKE YOUNG MEGALODONS GREW UP IN TROPICAL NURSERIES.

Rodrigo Arangua, AFP/Getty Images

Great whites, hammerheads, and a few other 21st century sharks give birth in relatively safe zones biologists call “nurseries.” These are shallow waters where big predators are few and far between. Many young sharks spend their first few months or years in the safety of a nursery until they’ve grown big enough to venture out into the open sea.

Megalodon young may have done the same. Down in Panama, there’s a 10-million-year-old geologic site with an unusually high concentration of small megalodon teeth. Since the vast majority came from adolescent sharks who would have been 7 to 35 feet long, it’s thought that the area was once a megalodon nursery. Florida’s Bone Valley region may have been another mass birthing site for the species.

13. THOMAS JEFFERSON OWNED A MEGALODON TOOTH.

The two-dollar founding father was an avid fossil fan: Jefferson gathered and wrote about mastodon bones, along with the claws of what he thought was a giant lion but turned out to be an ice age ground sloth. One of the most interesting fossils Jefferson owned was a megalodon tooth from South Carolina, a specimen that bears his signature on the enamel. His collection of prehistoric animal remains resides at the Academy of Natural Sciences in Philadelphia.

14. THERE’S NO EVIDENCE THAT MEGALODON IS STILL ALIVE.

The youngest megalodon remains in the fossil record are around 2.6 million years old. Hypotheses on why the super predator disappeared after that point are numerous and varied. Maybe competition from new sharks and whales that were appearing did megalodon in. Its extinction has been blamed on oceanic cooling as well, but this idea has recently been criticized.

No matter what killed the species off, the consensus among scientists is that megalodon is indeed deceased. It’s hard to sink a good sea monster story, though. Novels like the Meg series and other fictional works about megalodons who have somehow managed to survive into the 20th or 21st centuries are popular. But as marine biologist Craig McClain and many others have noted, there’s no compelling scientific reason to think that megalodon is still lurking in our oceans. McClain argued in Deep Sea News that “if Megalodon existed now we would not only see [Megalodon] teeth all over today, as we do for other sharks, but [we] would have fossilized ones from the last 2.6 million years. By the way, Megalodon teeth are pretty recognizable and distinctive, beyond just size, from other extinct sharks and the Great White.” So in other words, researchers would have no trouble distinguishing between megalodon teeth and those of extant sharks.

It also stands to reason that if the species was still around, newly-dead megalodons would wash up on the beach once in a while. We’d also find megalodon teeth embedded in the occasional whale corpse. No such evidence has ever arisen—and claims of a deep-sea megalodon population are highly unlikely. As paleobiologist Meghan Balk told The Daily Beast, “Megalodon fossils appear in shallower marine sediments. Plus, most large sharks occur in the upper 500 meters of the water column, probably due to productivity. The deep is much too nutrient poor to support such a large animal.”

15. IT'S ABOUT TO STAR IN A MOVIE.

After more than 20 years languishing in development hell, Steve Alten’s classic shark novel Meg—which launched a series of books—is finally being made into a movie. The Meg, which will hit theaters on August 10, stars Jason Statham as a rescue diver tasked with saving the crew of a deep sea observation program whose undersea workstation has been disabled after being attacked by the thought-to-be-extinct creature.

Additional Sources: Megalodon: Hunting the Hunter; The Story of Life in 25 Fossils: Tales of Intrepid Fossil Hunters and the Wonders of Evolution