PREHISTORIC SHARKS

1. PREHISTORIC SHARKS

2. PART 1 THE MEGALODON

3. IMAGES FOR THE PRESENTED SHARK MEGALODON

4. CONTENTS • 1. Megalodon’s bite • 2. Megalodon's teeth. • 3. Megalodon’s length. • 4. Megalodon was much bigger than prehistoric reptiles like Liopleurodon. • 5. Megalodon lunched on giant whales. • 6. Megalodon may have disabled their prey by biting off their fins. • 7. Megalodon's closest living relative is the Great White Shark. • 8. Megalodon fossils have been found all over the world. • 9. No one knows why Megalodon went extinct. • 10. Megalodon’s teeth were once described as "tongue stones."

5. MEGALODON Not only was Megalodon the biggest prehistoric shark that ever lived; it was the biggest predatory marine creature in the history of the planet, outweighing both modern Great white sharks and ancient reptiles like Liopleurodon and Kronosaurus. Here are facts you may or may not have known about this lethal predator:

6. MEGALODON 1. Megalodon’s bite In 2008, a joint research team from Australia and the U.S. used computer simulations to calculate Megalodon's biting power. The results can only be described as terrifying: whereas a modern Great white shark chomps with about 1.8 tons of force (and a lion with a wimpy 600 pounds or so), Megalodon chewed down on its prey with a force of between 10.8 and 18.2 tons enough to crush the skull of a prehistoric whale as easily as a grape.

7. MEGALODON 2. Megalodon's teeth. Megalodon didn't earn its name "giant tooth" for nothing. The teeth of this prehistoric shark were over half a foot long, serrated, and heart-shaped (by comparison, the biggest teeth of a Great white shark are only about three inches long). You have to go back 65 million years to none other than Tyrannosaurus-Rex to find a creature with consistently bigger choppers, though the canines of some saber-tooth cats also measured up.

8. MEGALODON 3.Megalodon’s length. Since Megalodon is known for thousands of teeth but only a few scattered bones, its exact size has been a matter of debate. Over the past century, paleontologists have come up with estimates (based mainly on tooth size and analogy with modern Great White Sharks) ranging from 40 to 100 feet, but the consensus today is that adults were 55 to 60 feet long and weighed as much as 100 tons and some superannuated individuals may have been even bigger.

9. MEGALODON 4. Megalodon was much bigger than prehistoric reptiles like Liopleurodon. The ocean's natural buoyancy allows "top predators" to grow to massive sizes, but none were more massive than Megalodon. The giant aquatic reptiles of the Mesozoic Era, like Liopleurodon and Kronosaurus, only attained weights of 30 or 40 tons, and a modern Great white shark can only aspire to a relatively puny 3 tons. The only marine animal to outclass Megalodon is the blue whale, individuals of which have been known to weigh well over 100 tons.

10. MEGALODON 5. Megalodon lunched on giant whales. Although the bigger-than-Megalodon blue whale is technically a carnivore, it feeds mostly on tiny krill. Megalodon had a diet more befitting an apex predator, feasting on the prehistoric whales that swam the earth's oceans during the Pliocene and Miocene times, but also chewing down on dolphins, squids, fish, and even giant turtles (whose shells, as tough as they were, couldn't hold up against 10 tons of biting force).

11. MEGALODON 6. Megalodon may have disabled their prey by biting off their preys’ fins. According to at least one analysis, Megalodon's hunting style differed from that of modern Great white sharks. Whereas Great whites dive straight toward their prey's soft tissue (say, a carelessly exposed underbelly), Megalodon's teeth were suited to biting through tough cartilage, and there's some evidence that it may have first sheared off its victim's fins (rendering it unable to swim away) before lunging in for the final kill.

12. MEGALODON 7. Megalodon's closest living relative is the Great White Shark. Technically, Megalodon is known as Carcharadon megalodon meaning it's a species (Megalodon) of a larger genus (Carcharodon). Also technically, the modern Great white shark is known as Carcharodoncarcharias, meaning it belongs to the same genus as Megalodon. However, not all paleontologists agree with this identification, claiming that Megalodon and the Great White arrived at their striking similarities via the process of convergent evolution.

13. MEGALODON 8. Megalodon fossils have been found all over the world. Unlike some marine predators of prehistoric times, which were restricted to the coastlines or inland rivers and lakes of certain continents,Megalodon had a truly global distribution, terrorizing whales in warm-water oceans all over the world. Apparently, the only thing keeping adult Megalodon's from venturing too far toward solid land was their enormous size, which would have beached them as helplessly as 16th-century Spanish galleons.

14. MEGALODON 9. No one knows why Megalodon went extinct. Megalodon was huge, relentless, and the apex predator of the Pliocene and Miocene times. What went wrong? Well, there's no lack of theories: Megalodon may have been doomed by global cooling (which culminated in the last Ice Age), or by the gradual disappearance of the giant whales that constituted the bulk of its diet. (Some people think Megalodon still lurk in the ocean's depths, but there's absolutely no evidence to support this.)

15. MEGALODON 10. Megalodon’s teeth were once described as "tongue stones." Because sharks are constantly shedding their teeth, thousands and thousands over the course of a lifetime. Megalodon teeth have been found all over the world, from antiquity to modern times. It was only in the 17th century that a court physician named Nicholas Steno identified peasants' prized "tongue stones" as shark teeth; for this reason, some experts describe Steno as the world's first paleontologist!

16. PART 2 THE STETHACANTHUS

17. IMAGES FOR THE PRESENTED SHARK STETHACANTHUS

18. CONTENTS • 1. Stethacanthus’ history • 2. Stethacanthus’ body parts

19. STETHACANTHUS 1. Stethacanthus’ history Little is known about Stethacanthus. Most researchers say it is a weird-looking shark with its first dorsal fin flat and with spikes on it. More spikes were on its head.Stethacanthus is an extinct genus of shark which lived in the earlyCarboniferous epoch, around 360 million years ago. Fossils have been found in Europe and North America. Stethacanthus was around 70 centimeters (2.3 ft) long, and in many respects, had a typical shark-like appearance.

20. STETHACANTHUS 2. Stethacanthus’ body parts Stethacanthus was relatively small, but a dangerous, hydrodynamic predator that posed a constant menace to small fish as well as other, smaller sharks. What really set this genus apart was the strange protrusion, often described as an "ironing board" that jutted out from the backs of the males. Because the top of this structure was rough, rather than smooth, experts have speculated that it may have served as a docking mechanism that attached males securely to females during the act of mating.

21. PART 3 THE DUNKLEOSTEUS

22. IMAGES FOR THE PRESENTED SHARK DUNKLEOSTEUS

23. CONTENTS • 1. Properties • 2. Dunkleosteus’ diets and mating • 3. Imagine… • 3. Imagine… (continued) • 3. Imagine… (continued)

24. DUNKLEOSTEUS 1. Properties Dunkleosteus looked like the violent brute it was: powerfully built and armor-plated round its head. It was streamlined and shark-like. Dunkleosteus lacked true teeth, instead it had two long bony blades that could snap and crush almost anything. Pigment cells suggest Dunkleosteus had dark colors on its back and was silvery on its belly.

25. DUNKLEOSTEUS 2. Dunkleosteus’ diets and mating This fish was anything but picky with its food. It ate fish, sharks and even its own kind. And it seems that Dunkleosteus suffered from indigestion as a result: its fossils are often associated with regurgitated, semi-digested remains of fish. It included Stethacanthus in its diet. Dunkleosteus may have been one of the earliest animals to exist as male or female, meaning that pairs of fish had to mate physically.

26. DUNKLEOSTEUS 3. Imagine… Picture yourself submerged in an ancient sea, 400 million years ago. Above, a large shape appears, gliding powerfully through the water. Its head and trunk are covered with bony plates of armor, and the great, jagged jaws are like a primitive slicing machine, roughly made but clearly effective. This is Dunkleosteus, one of the first jawed vertebrates, and one of the largest of the armored fishes called placoderms. The fossil record indicates that this fish was an aggressive predator.

27. DUNKLEOSTEUS 3. Imagine… (continued) Some placoderm fossils contain evidence of gouges and scrapes and cuts in the surface of the large bones, matching fairly well to the serrated edges of Dunkleosteus jaw bones; others show that puncture wounds go right through the bones. The serrated, razor-sharp edges of bones in Dunkleosteus' jaws served as cutting edges. As they rubbed against each other, the opposing jaw blades were like self-sharpening shears. These bones grew continually, regenerating as they were worn down by usage.

28. DUNKLEOSTEUS 3. Imagine… (continued) Dunkleosteus was undoubtedly a powerful swimmer, much like today's large sharks. Its twenty-foot-long, muscular body ended in a shark-like tail. Its features are clearly those of a predator, and there were plenty of fish to feed on in the Devonian seas. Its prey may well have included primitive sharks, which did not achieve great size and diversity until Dunkleosteus and the other placoderms had disappeared from the oceans.

29. THE END THANKS FOR WATCHING MADE BY AREL NISSEN !!!

30. WEBLINK IF YOU WANNA SEE A COOL VIDEO ABOUT THE DUNKLEOSTEUS AND THE STETHACANTHUS< CLICK HERE: http://www.youtube.com/watch?v=HwvvkGqOr-Y