Talk about a raw deal: when the "type fossil" of Oviraptor was unearthed, sitting atop a clutch of fossilized eggs, the eggs were thought to belong to an entirely different kind of dinosaur, Protoceratops (specimens of which had been found in the immediate vicinity, in central Asia). Naturally, it was assumed that the new dinosaur had stolen the eggs, hence its name, Greek for "egg thief."

Although it's stuck with its inaccurate moniker, Oviraptor has since been completely vindicated. Paleontologists now believe that the "guilty" specimen had actually been brooding its own eggs, and earned its notoriety simply by being a good mother (or possibly a good father, since Oviraptor males could conceivably have played a big role in child-rearing).

Beyond this little snafu, Oviraptor was one of the most birdlike of all dinosaurs, with a sharp, toothless beak and (probably) a coat of feathers. This theropod didn't possess wings, but it seems to have been a short step away (in evolutionary terms) from the first flying birds. (By the way, despite its name, Oviraptor doesn't technically count as a true raptor, the breed of dinosaurs most famously represented by Deinonychus and Velociraptor.)

Read more about dinosaurs like Oviraptor: Dino-Birds - The Small, Feathered Dinosaurs

Illustration of Oviraptor: Nobu Tamura

Once considered to be a close relative of Iguanodon, paleontologists have now classified Ouranosaurus as a hadrosaur (duck-billed dinosaur)--albeit one with a major difference. This plant-eater had rows of spines jutting out vertically from its backbone, which has fueled speculation that it Ouranosaurus may have sported a sail, like the meat-eating Spinosaurus or the much earlier pelycosaur Dimetrodon. However, some experts insist that Ouranosaurus didn't have a sail at all, but a flattened, camel-like hump.

If Ouranosaurus did in fact possess a sail (or even a hump), the logical question is, why? As with other such reptiles, this structure may have been served as a temperature-regulation device, and it may also have been a sexually selected characteristic (that is, Ouranosaurus males with bigger sails had the opportunity to mate with more females). A fatty hump, on the other hand, could have functioned as a last-ditch reserve of food and water, the same purpose it serves in modern camels.

Read more about dinosaurs like Ouranosaurus: Hadrosaurs - The Duck-Billed Dinosaurs

Illustration of Ouranosaurus: Nobu Tamura

China's Liaoning fossil beds have yielded a rich array of dino-birds, small, feathered theropods that represent intermediate stages in the slow evolution of dinosaurs into birds. Surprisingly, this same location has yielded the only known specimen of Liaoningornis, a tiny, true prehistoric bird from the early Cretaceous period that looked more like a modern sparrow or pigeon than any of its more famous feathered cousins. Helping to nail down its avian bona fides, the feet of Liaoningornis show evidence of the same "locking" mechanism (or at least the long, curved claws) that helps modern birds perch securely in the high branches of trees.

Read more about prehistoric birds like Liaoningornis: Prehistoric Birds - The Story of Bird Evolution

Illustration of Liaoningornis: Wikimedia Commons

It's not as well known as the Cave Bear or the Cave Lion, but the Cave Hyena (Crocuta crocuta spelaea) was a common sight in Pleistocene Europe and Asia, to judge by this megafauna mammal's numerous fossil remains. As you can guess from its name, the Cave Hyena liked to drag its kill (or, more often, the kill of other predators) back to its den, and it possessed longer, more muscular hind legs than contemporary hyenas (of which the Cave Hyena is classified as a subspecies, rather than a separate species as had previously been thought). One group of caves in Europe has yielded tantalizing evidence about the Cave Hyena's favorite prey animals, with Przewalski's Horse and the Woolly Rhino figuring high up on the dinner menu.

Like most opportunistic predators of the Pleistocene epoch, Cave Hyenas occasionally hunted early humans and hominids, and they weren't shy about stealing the hard-earned kill of packs of Neanderthals. Where Crocuta crocuta spelaea and the ancestors of modern humans really mixed it up was in competing for living space: paleontologists have unearthed caves bearing alternating evidence of populations of Cave Hyenas and populations of Neanderthals, evidence of a pitched, thousands-of-years-old land battle. In fact, the Cave Hyena may have been doomed by the encroachment of early humans on its rapidly dwindling caves, which grew even scarcer after the last Ice Age.

Read more about prehistoric mammals like the Cave Hyena: The Giant Mammals of the Cenozoic Era

Photograph of the Cave Hyena: Wikimedia Commons