Megatooth Shark

Scientific name: Carcharocles megalodon Scientific classification: Phylum: Chordata Class: Chondrichthyes Order: Lamniformes Family: Lamnidae

Megatooth Shark—A tooth of the fearsome great white shark, right, looks very small indeed next to the tooth of the megatooth shark, left. (Ross Piper)

Megatoothed Sharks

Megatooth Shark—The megatooth shark, top and center, was at least 20 times heavier than the living great white shark, bottom left and bottom right, making it the largest predatory fish that has ever lived. (Renata Cunha)

Megatooth Shark—A tooth of the fearsome great white shark, right, looks very small indeed next to the tooth of the megatooth shark, left. (Ross Piper)

Megatooth Shark—The megatooth shark, top and center, was at least 20 times heavier than the living great white shark, bottom left and bottom right, making it the largest predatory fish that has ever lived. (Renata Cunha)

When did it become extinct? The megatooth shark is thought to have become extinct around 1.6 million years ago. Where did it live? This shark appears to have had a global, subtemperate distribution as its fossils have been found in Europe, Africa, North and South America, southern Asia, Japan, Indonesia, Australia, New Caledonia, and New Zealand.

The great white shark (Carcharodon carcharías) is one of the most formidable predators in the ocean, yet it would be dwarfed next to the megatooth shark—the largest predatory fish that has ever lived. As its name suggests, megatooth's mouth bristled with an abundance of triangular, serrated teeth that make a great white's dentition look pretty tame.

Sharks and their relatives have a skeleton composed mainly of cartilage, which in life is a very light and flexible frame. In death, however, this frame rots away to nothing as there are no minerals, for example, apatite, that can be replaced by other minerals to form fossils. Due to this quirk of anatomy, all that remains to testify to the existence of this fantastic fish are its immense teeth and disc-shaped parts of the vertebrae known as centra. Many teeth have been found, some of which have been recovered in dredges of sediment from the seabed, while others have been found in quarries in various locations around the globe. The appearance of the shark has been extrapolated from these remains. The teeth can be used to reconstruct the upper and lower jaw, and a body can be built around what must have been a cavernous mouth.

The adult size of this shark is a bone of contention among experts. Some recent calculations estimate the body length of this animal to be 16 m, with a weight of approximately 48 tonnes. By comparison, the largest great white sharks alive today are around 6 m long and 1.9 tonnes. Even these conservative estimates of the megatooth's length and weight suggest a truly terrifying creature that once patrolled the seas of the prehistoric earth. We know that the megatooth was a very large animal, but what did it look like? We can only guess, but for a long time, it was assumed to look like a giant great white. It is now reckoned to have had the same general body shape as the great white, but with a heavier head, more massive jaws, and longer pectoral fins—obviously, these reconstructions must be treated with caution as they based are nothing more than teeth and bits of backbone.

The megatooth shark was undoubtedly a predator, but what did it eat and where did it hunt? The remains that have been found suggest that the shark was an inhabitant of shallow, warm to cool temperate coastal waters—habitats that were commonplace around 10 million years ago. These waters were home to a wealth of marine mammals that had evolved from ancestors that took to the water not long (in geological terms) after the extinction of the dinosaurs. This marine mammal fauna consisted of whales, seals, sea lions, and the extinct relatives of dugongs and manatees. It is probable that the megatooth shark ate all these animals, but it may have been a specialist predator of whales. Fossils of extinct whales have been found bearing deep gashes the right size and shape to have been inflicted by the slashing teeth of the megatooth shark. You can just imagine this 50-tonne shark slamming into the side of an ancient, 10-m-long baleen whale and tearing out a huge chunk of blubber and flesh. Like the great white shark, megatooth probably retired to a safe distance after this initial strike to let the prey bleed to death before closing in to feast. Its food requirements must have been enormous, and if the great white shark is anything to go by, it may have needed about one-fiftieth of its weight in food every two weeks, which, for a fully grown megatooth, was about 1 tonne of meat. An adult megatooth was able to tackle whales, but what did these sharks eat when they were young? They probably fed on large fish and may have had different teeth from the adults, up to the job of keeping a firm grip on slippery fish. The teeth of a young great white are more slender and narrow than those of the adult to provide an advantage in catching fast-moving fish.

Even though the adult megatooth shark must have been the undisputed king of the sea, the great white shark—one of the most impressive predators alive today—actually coexisted with the megatooth. How did these two enormous predatory fish manage to live at the same time without coming into direct competition with one another? They may have managed to coexist by feeding on different prey. As the great white is much smaller than the megatooth, its preferred prey is seals and sea lions, while megatooth was capable of attacking and killing whales. The great white is still around today doing the same thing it has done for millions of years, but all that remains of the megatooth are petrified fragments of its body. What happened to this giant shark?

The megatooths massive appetite probably made it very vulnerable to the ravages of global cooling, which entered a harsh phase around 2 million years ago. Temperatures at midlatitudes dropped by around 15 degrees Celsius, and as more and more water got locked up in the growing glaciers, megatooth's shallow water habitats became scarcer and colder, and the shark was forced into dwindling pools of habitat, unable to catch sufficient prey to fuel its enormous bulk. Some of the whales on which megatooth probably fed also became extinct at around the same time, supporting the theory that shallow, warm-water habitats disappeared due to global cooling.

♦ The megatooth shark existed for around 20 million years, and although it is often assumed to be a close relative of the great white, their exact relationship is still uncertain.

♦ Although adult megatooth sharks were at the very top of the food chain, the young were fair game for many marine predators.

♦ Sharks have the amazing ability to continually replace their teeth. As a tooth breaks off or is shed, the first in a line of growing replacements moves forward to fill the gap.

For this reason, shark teeth are very common in the fossil record and have been known for centuries—often known by the name of "glossopetrae" (Greek glosso translates as "tongue" and petrae translates as "stone"). Even Pliny the Elder, the Roman naturalist, wrote about them, believing them to fall from the sky during lunar eclipses. They were later assumed to be serpent's tongues that St. Paul had turned to stone.

♦ It has been suggested that the megatooth shark may still survive, but continued survival implies a viable population. In reality, there is no chance that such a huge, surface-dwelling predator could escape detection in the modern age.

Further Reading: Klimley, A. P., and D. G. Ainley, eds. Great White Sharks: The Biology of Carchar-don carcharias. San Diego: Academic Press, 1996; Tschernezky, W. "Age of Carcharodon megalodon? Nature 184 (1959): 1331-32.

Magnificent Teratom—The magnificent teratorn was the largest flying bird that has ever lived. At 6 to 8 m, its wingspan was about the same as a small airplane. (Renata Cunha)

Scientific name: Argentavis magnificens Scientific classification: Phylum: Chordata Class: Aves Order: Ciconiiformes Family: Teratornithidae

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  • Gloriana Gardner
    What is a megatooth shark?
    8 years ago
  • dennis
    Is the megatooth shark and megalodon the same thing?
    8 months ago

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