1. Rodhocetus gives us a clear example of a species evolutionary transition from landdweller to seafarer. One of the bestknown animals in the Cetacea infraorder (which includes whales, dolphins, and porpoises), Rodhocetus had short limbs ending in webbed hands and feet. Its characteristics closely resemble those of land mammals, thus leading scientists to conclude it was partway along the evolutionary transition from land to sea. .....
2. If every letter in Pelagornithidaes name was equal to a foot, it still wouldnt equal the size of this massive prehistoric creature. Boasting a wingspan between 1520 feet (56 m), Pelagornithidae were the dominant seabirds of most oceans and even brushed up with our earliest ancestors. .....
3. Made popular by the Smithsonian Channel TV Show, Titanoboa is simultaneously the largest, heaviest, and longest snake known to man. Appearing during the Paleocene age just after the extinction of dinosaurs, Titanoboa was so muscular it crushed its gigantic prey to death with massive force. Its discovery was especially important as it showed Earths tropical areas were likely warmer than we expected. .....
4. Nicknamed the shovel tusker, the Platybelodon looks like a modern day elephant with one major difference: its trunk. This strange prehistoric creature did not have a typical fleshy trunk but rather a flat protrusion comparable to an elongated ducks bill. Scientists believe it used the shovel tusks to grasp tree branches and rip off bark. .....
5. A combination of two of humans biggest fears alligators and scorpions Eurypterid was like a scorpion which, from one found fossil, could reach the size of an alligator. Primarily an oceandweller, this creature was not a true scorpion. Found all over the world, Eurypterid finally went extinct during the PermianTriassic extinction event 252.17 million years ago. Most only grew up to 8 inches (20 cm) long, but the infamous subspecies Jaekelopterus w .....
6. Pterodaustro is one of the best known pterosaurs (flying reptiles) in the world. Found in South America, the Pterodaustro notably used a thousand bristlelike teeth protruding from its lower jaw to filter plankton and small crustaceans as it waded through shallow pools. The bill with teeth accounted for up to 85% of its head. .....
7. Only a few inches long with five eyes to navigate its seafloor home, Opabinia looks like it could have been a mad scientists invention. Though not a fierce predator, Opabinia was an oddlooking prehistoric creature sporting a unique, vacuum hoselike attachment at its mouth which it used to bring food back to its mouth (much like an elephants trunk). Beyond its five eyes, it also had 30 flippers. .....
8. If you get scared by a wasp or a bee, you wouldnt have fared too well in prehistoric times. Meganeura (the name sounds big enough) was prehistoric times massive dragonfly. With a tiptotip wingspan up to 2.5 feet (75 cm), Meganeura was large enough to devour frogs and small amphibians and is the largest known flying insect species. .....
9. By far one of the strangest prehistoric creatures on this list is Hallucigenia. At max 1.38 inches (3.5 cm) long, this creature was originally constructed upside down and with its back and front reversed when scientists first created models. An ancestor to either arthropods or worms, Hallucigenia had 7 or 8 pairs of legs with rigid spines correspondingly coming out the top of its body. .....
10. About the size of a VW Bug, the Glyptodon was an armadillolike creature which actually would be more related to modernday turtles. Sporting over 1 inchthick (2.5 cm) scales, the Glyptodon was a herbivore and, unlike turtles, could not retract its head; instead, it had a bonelike cap on its head. .....
11. Translated from Greek to mean crowned crocodile, Estemmenosuchus is quite a strange looking prehistoric creature. Though it looked like a hipporhino mix, this creature had distinctive knoblike horns on the sides of its head (and, in some species, on the top and on the jawbone). Thankfully, it was primarily a herbivore. .....
12. Capybaras arent feared animals today, but this prehistoric animal was far from cute and cuddly. Nicknamed the bear dog, Arctocyon could walk around on its hind legs and tear apart whatever it sunk into with its razor sharp teeth. .....
13. Though it looked like a squished (though terrifying) sardine, Dunkleosteus holds the record for the strongest bite of any animal, living or extinct. Able to fit a human in its mouth with one chomp, this bizarre prehistoric creature ruled the seas for 20 million years, leaving destruction in its wake. A pure carnivore, Dunkleosteus could weigh as much as an elephant and reach up to 33 feet (10 m) in length. .....
14. Flightless birds with similar characteristics to the ostrich, Phorusrhacids could reach land speeds comparable to cheetahs. Up to 1,000 pounds (454 kg) and 9 feet (3 m) tall, these creatures could easily grasp a mediumsized dog in a single bite (and their hooked bill allowed them to tear into larger animals as well.) They really deserve their nickname, the terror bird. .....
15. If youve ever experienced whiplash, you can imagine how tough a life this plesiosaur had. With a body which was mostly neck, Elasmosaurus was originally put together by paleontologists the wrong way: with a short neck and elongated tail. (It was also originally depicted as having a flexible, snakelike neck which has since been refuted.) Measuring about 46 feet (14 m), Elasmosaurus prowled the oceans at a length of nearly four Mini Coopers endtoen .....
16. Dunkleosteus may have been big, but Helicoprion holds this lists top spot for most bizarre, seadwelling prehistoric creature. Helicoprion was an ancient sharklike fish with a modified jaw: its lower palate was a circular saw of teeth which could tear flesh from bone, grinding the flesh against its top teeth. .....
17. Related to the Helicoprion, Edestus Giganteus was as terrifying as it was strange. Commonly referred to as the scissortooth shark, Edestus Giganteus had an interesting set of chompers. Rather than replace its teeth as they wore out, it would grow new teeth and gums at the back of its mouth, pushing older teeth and gums out of its mouth. The older teeth would eventually protrude and hang out of its mouth. .....
18. Diprotodon Optatum is the largest known marsupial (mammal with a pouch) to have ever existed. About the size of a hippopotamus and comparable to a wombat with saggier skin, Diprotodon Optatum lived in Australia during the Pleistocene period and may have run across our relativelynear indigenous ancestors. .....
19. Linhenykus doesnt look that different from our general conception of dinosaurs bar one big (well, little actually) feature: its finger. Linhenykus had only one tiny finger on each of its arms, the only nonavian dino to have but one. Scientists still arent sure the purpose, especially given its large feet. .....
20. Longisquama is a lizardlike creature with what appears to be hockey sticks longer than its whole body jutting out of its back. Paleontologists know little about this reptile found in Central Asia and a longstanding debate continues on whether Longisquama was a prehistoric bird or something else entirely. .....
21. With the ability to glide similar to deltawinged (triangleshaped) aircraft, Sharovipteryx was a master of longdistance travel. Found in Kazakhstan, this onefootlong (30 cm) prehistoric creature had membranes attached above and below its hind legs which provided for gliding (but not flight). .....
22. In contrast to most of the massive prehistoric creatures on this list, Epidexipteryx was a tiny prehistoric creature. Presumably the first example of ornamental feathers (think of a peacock), Epidexipteryx grew up to 17.5 inches (44.5 cm) with almost half of that encompassing just the tail feathers. This feathered dinosaur lived during the Middle or Upper Jurassic age throughout Inner Mongolia. .....
23. A legendary creature possibly referred to as the serpent god in Aztec mythology, Quetzalcoatlus was as tall as a giraffe while roaming on its feet. Once it took to the sky, its wingspan was from 3040 feet (1012 m) thats as long as most buildings in Paris are high. A lizardlike creature, Quetzalcoatlus may also have been what our ancestors referred to as dragons. .....
24. Sporting an upper dorsal fin which looked like the top part of the Starship Enterprise, an adult male Stethacanthus lived about 320 million years ago. A pretty typical shark otherwise, Stethacanthus likely used its unique dorsal fin in mating rituals or to scare away predators. .....
25. The TRex pales in comparison to the massive but lesserknown Spinosaurus. Reaching up to 59 feet (18 m) long, this prehistoric beast could weigh more than a semitruck and the webbed spines on its back could have easily reached the height of a basketball player. Spinosauruss alligatorlike mouth likely means it was a major fish eater and spent much time in the water. Makes us wonder whether those back spines could have been used for swimming. .....
26. This was an ancient relative of todays sperm whale, which as we all know (or should know) is huge, eats lots of squid and has never been known to attack humans without provocation. Acrophyseter was the complete opposite; it was moderately sized, and didnt feed on squid but rather on other marine mammals and even on sharks! Its horriblelooking teeth were deadly weapons and have given Acrophyseter and its ancient relatives the nickname of killer sp .....
27. Its name says it all; it was a monstrous ape, closely related to the orangutan, that roamed the bamboo forests, jungles and mountains of China, India and Vietnam during the Pleistocene. It was a vegetarian, but scary nonetheless; it could grow up to three meters tall and weigh up to 550 kgs! Its strength must have been extraordinary and probably kept it safe from most predators. It finally went extinct 300.000 years ago, possibly due to overhunti .....
28. Epicyon could well be described as a giant pitbull on steroids. It was a member of the Canidae or dog family, but whereas modern day canids are built for speed and endurance, Epicyon was built for brute strength, and had jaws so powerful that they could crush bone as if they were crackers! This beast ruled the plains of North America for fifteen million years, before it was replaced by big cats (including sabertooths). .....
29. Madtsoia would be the worst nightmare of anyone with a phobia of snakes. Although only fragmentary remains are known, it is claimed to have reached the immense length of 1520 meters! This creature appeared in the Cretaceous period and possibly dined on dinosaurs. It was similar to todays boas and pythons in that it was not venomous, but rather squeezed its victims to death using its immense muscular strength. Madtsoia was such a successful predat .....
30. Purussaurus was a gigantic caiman (a relative to alligators) that lived in what is today known as the Amazonian rainforest. Back in Purussaurus days, 8 million years ago, that region was actually a vast inland sea teaming with crocodiles, gharials, fresh water whales, giant rodents and enormous turtles. Purussaurus was the top predator in that sea, and with good reason; at 1215 meters long, maybe more, it was one of the largest crocodilians ever .....
31. Although pigs, wild boars and warthogs today are known to eat meat on occasion, they are basically vegetarian. On the other hand, the Entelodon, a prehistoric pig relative, was a full time carnivore and possibly one of the most monstrouslooking mammals ever. Standing on all fours, this beast was as tall as a man, and had an immense head armed with powerful jaws and sharp teeth. Scientists believe that it was able to hunt live prey, but that it al .....
32. This is by far the smallest creature of the list, but it would still cause hysteria, and perhaps even some heart attacks, if it showed up today. It was very similar to todays scorpions but could grow up to one meter long, perhaps more, and was armed with sharp chelae (claws) and a venomous stinger. Of course, we dont know how toxic its venom was, but considering the considerable amount it injected with each attack, it was most likely a very deadl .....
33. This is a fairly well known prehistoric monster, but it is just so big and scary that it deserves to be in this list. Megalodon (technically called a Carcharocles megalodon) was a gigantic shark, closely related to todays makos and great whites. It could grow up to 20 meters long and weigh up to 60 tons, being almost six times larger than Tyrannosaurus rex! Obviously, the only thing in the sea big enough to feed Megalodon where whales, and indeed .....
34. Since the formidable Smilodon (better known as sabertoothed tiger) is too well known, we have decided to go for a refreshing change. Enter Xenosmilus, possibly the nastiest feline ever to have existed. The remains of this very large cat (the size of a lion or tiger, but more robust) were recently found in Florida along with the remains of many unlucky giant peccaries (similar to wild pigs) that fell prey to it. Instead of strangling prey or break .....
