1. Therizinosaurus
Kind of like Big Bird crossed with Count Dracula, Therizinosaurus was a large type of theropod dinosaur known as a therizinosaur, with a squat trunk, a long neck, a tiny head, and a trio of three-foot-long claws on each of its hands (hence its name, Greek for "reaping lizard").
2. Stygimoloch
Roughly translated as "horned demon from the river of hell"--is a
good indication of Stygimoloch's weirdness quotient.
3. Tanystropheus
Not technically a dinosaur, but an archosaur, Tanystropheus is the closest nature has ever come to evolving a living fishing pole. ThisTriassic reptile's neck was over 10 feet long, compared to only five feet for the rest of its body; clearly Tanystropheus made its living by perching on riverbanks, dipping its head into the water, and snagging unwary fish.
4. Carnotaurus
Everyone likes to make fun
of Tyrannosaurus Rex's arms, which looked like they belonged on a
dinosaur one-tenth its size. But the nubbinlike arms and hands of Carnotaurus made T. Rex look like an Olympic swimmer: This may be the closest nature has ever come to rendering a reptile's hands completely defunct (with the obvious exception of snakes, of course).
5. Suchomimus
Evolutionarily speaking,
dinosaurs and crocodiles both branched off fromarchosaurs at the end of the Triassic period, and thereafter maintained fairly
distinct lifestyles. Suchomimus looked like a bizarre hybrid of these two families: This large theropod had the body of a carnivorous dinosaur, but the long, narrow, toothy snout of a crocodile (which it presumably used to snatch prehistoric fish out of lakes and rivers).
6. Brachytrachelopan
Every dinosaur rule has at least one exception, and Brachytrachelopan is the exception to the rule that all sauropods had equally long necks and tails. This dinosaur's neck was almost comically short compared to more famous relatives like Diplodocus and Apatosaurus, most likely because Brachytrachelopan evolved not to nibble the tops of trees, but waist-high underbrush. More about Brachytrachelopan
7. Jeholopterus
Most of the pterosaurs of the Mesozoic Era were characterized by
their long, narrow, dangerous-looking beaks. Not Jeholopterus, though, whose beakless, double-fanged jaws resembled those of a large tabby. Even more weirdly, one paleontologist speculates that Jeholopterus was the Jurassic equivalent of a vampire bat, biting the flanks
of largesauropods and sucking their blood. More about Jeholopterus
8. Ouranosaurus
make of the spines that jutted out of Ouranosaurus' backbone: Some think they supported a thin sail of skin, akin to that of Spinosaurus, while others speculate that this ornithopodsported a camel-like hump filled with fatty tissue. The latter is a distinct possibility, especially since Ouranosaurus to have led a very camel-like existence in the parched regions of northern Africa.
9. Cryolophosaurus
Cryolophosaurus makes the top-10 weirdness list on two accounts: First, this is one of the few dinosaurs ever to be unearthed in modern-day Antarctica, and second, the decorative crest atop this large theropod's noggin was oriented from side to side, rather than from front to back. This makes Cryolophosaurus look as if it's sporting a
10. Thrinaxodon
As therapsids go, Thrinaxodon wasn't especially strange;
it's included on this list because its weirdness is typical of therapsids in general. From all the available evidence, this "mammal-like reptile" (which lived alongside the earliest dinosaurs) sported a coat of fur, a black, wet nose, and probably a warm-blooded metabolism. Paleontologists think it looked a bit like a modern badger.
SOURCE – (dinosaurs.about.com/od/typesofdinosaurs/tp/weirdestdinosaurs)