Dinosaurs by their nature seem bizarre, larger than life -- mysterious. And the history of dinos is constantly rewritten. Here we present to you 10 dinos that are furrier, freakier and more colorful than we previously thought possible.
Head-butting pachycephalosaurs, with noggins shaped like built-in football helmets, have long puzzled paleontologists.
"The head-slapping behavior of crocodiles and the face-pecking observed in a variety of birds suggest that 'using your head' is not unique to pachycephalosaurs," says Joseph Peterson, a geology professor at the University of Wisconsin. "Domes likely evolved in response to such behavior."
Some researchers believe the ancient bird Confuciusornis had leg feathers, which formed another pair of wings.
Scientists now think that some dinos that flew didn't have two wings. They had four.
"The first birds descended from four-winged dinosaurs," says renowned dinosaur and early avian hunter Xing Xu, a professor at the Chinese Academy of Sciences. One such dinosaur might have been Microraptor, a non-avian dino that had feathers on both its arms and legs.
OK, full disclosure: This dino doesn't exist yet. But even conceptually it's bizarre enough to be included in this list. It's a dino -- and it's a chicken. It's a Dinochicken.
Paleontologist Jack Horner and his colleagues have been genetically engineering chickens to reactivate ancestral traits, such as long tails, which are more associated with non-avian dinosaurs.
"Birds are dinosaurs," Horner told Discovery News. "So technically we're making a dinosaur out of a dinosaur."
Plant-eating dinosaurs called sauropods had the longest necks in the animal kingdom.
The sauropod family includes the largest terrestrial vertebrates that ever existed -- giant, lumbering beasts weighing tens or even hundreds of tons. They were 10 times the size of an elephant, and some of these dinosaurs' necks grew to 50 feet -- six times longer than a giraffe's.
When this Late Jurassic dino wasn't knocking things over with his whiplash tale, he was stealing somebody's wallet. Just look at the perpetual grin on Kaatedocus siberi -- you can't trust a dino like this.
Unearthed in Wyoming, Kaatedocus had "pencil-like teeth in the front part of the muzzle," said Octavio Mateus, one of the world's leading paleontologists. "Because those teeth were not adapted for chewing, Kaatedocus probably ingested gastroliths or gizzard stones."
Often artistic license is needed during reconstructions, but in this case the skull makes clear this dino's toothy grin.
Oviraptors -- relations of T. rex that lived during the Cretaceous period -- had feathers researchers say were used for mating displays, similar to modern-day peacocks and turkeys. Its name means "egg plunderer," because it was first discovered in the 1920s near eggs from another species.
Scientists now believe, however, that this dino was protecting the eggs instead of stealing them.
This stylish dinosaur predated the punk movement by 200 million years. Pegomastax africanus had sharp bristles and stabbing, self-sharpening fangs. Its remains were chipped out of red rock from South Africa.
The 2-foot-long dino weighed less than a modern house cat in the flesh. But Paul Sereno, a paleontologist and professor at the University of Chicago, believes it was a plucky survivor. "I think the bristles would have made it look at least a little bigger than it was -- perhaps they could poke out more strongly when excited," he said.
Some dinosaurs had russet-colored feathers, scientists say, and this jazzy specimen had a Mohawk crest and stripes. The Anchiornis huxleyi was a small, feathered, two-legged dinosaur that lived roughly 150 million years ago. The animal weighed just about four ounces (110 grams) and appears to have had a dark gray or black body and wings with white feathers that gave it a stripe pattern. It also had a reddish-brown crest and speckles on the face.
A male Xenoceratops didn't just impress with his 20-ton figure. It had massive spikes at the top of its head, two hooks jutting from its forehead, and a bumpy shield around his neck. Xenoceratops -- the name means "alien horned-face" -- was a relative of the Triceratops and used its impressive head gear to show dominance, say researchers, or to attract females.
It's the dinosaur you want to cuddle. OK, maybe not -- this thing is gigantic.
Like the diversity among birds today, not all feathered dinosaurs were lightweight, agile animals.
This massive tyrannosaur lived in China until about 65 million years ago. Yutyrannus huali, meaning "beautiful feathered tyrant," grew up to 30 feet long and could weigh more than 3,000 pounds.