When most people think of raptors, they picture the lithe, lizard-skinned, big-clawed dinosaurs of Jurassic Park, smart enough not only to hunt in packs but to figure out how to turn doorknobs. In real life, though, most raptors were about the size of children, almost certainly covered in feathers, and not quite as intelligent as the average hummingbird. (For the record, what Steven Spielberg called Velociraptors in Jurassic Park were really much bigger individuals of Deinonychus, but let's not quibble.) See a gallery of raptor pictures
The time has come to set the record on raptors straight. First, you might be surprised to learn that "raptor" itself is a semi-made-up, Hollywood-type name: paleontologists prefer to talk about "dromaeosaurs" (Greek for "running lizards"), which you have to admit isn't quite as catchy. And second, the raptor roster extends far beyond the mass-market Velociraptor and Deinonychus mentioned above, including such obscure (but important) genera as Buitreraptor and Rahonavis. (By the way, not all dinosaurs with the word "raptor" in their names are true dromaeosaurs; examples include such non-raptor theropod dinosaurs as Oviraptor and Eoraptor.)
The Definition of a Raptor
Technically, paleontologists define raptors (or dromaeosaurs) as theropod dinosaurs that share certain obscure anatomical characteristics. For our purposes, though, raptors can be broadly described as small- to medium-sized, bipedal, carnivorous dinosaurs equipped with grasping, three-fingered hands, relatively big brains, and (most distinctively) huge, solitary claws on each of their hind feet, which they probably used to slash and occasionally disembowel their prey. (Bear in mind that raptors weren't the only theropods of the Mesozoic Era; this populous class of dinosaurs also included tyrannosaurs, ornithomimids, and small, feathered "dino-birds.")
Then there's the issue of feathers. While it can't be flatly stated that every single genus of raptor had feathers, enough fossils have been unearthed bearing evidence of this unmistakably bird-like trait to lead paleontologists to conclude that feathered raptors were the norm, rather than the exception. However, feathers didn't go hand-in-hand with powered flight: while some genera on the fringes of the raptor family tree (such as Microraptor) seem to have been capable of gliding, the majority of raptors were completely land-bound. In any case, there's no question that raptors are closely related to modern birds; the word "raptor" is also used to describe big-taloned birds like eagles and falcons.
The Rise of the Raptors
Raptors came into their own during the late Cretaceous period (about 90 to 65 million years ago), but they roamed the earth for tens of millions of years before that. The most notable dromaeosaur of the early Cretaceous period was Utahraptor, a gigantic predator that lived about 50 million years before its more famous descendants; still, paleontologists believe that most proto-raptors of the late Jurassic and early Cretaceous periods must have been relatively tiny, scurrying beneath the feet of larger sauropod and ornithopod dinosaurs.
During the late Cretaceous period, raptors could be found all over the planet, with the exception of modern-day Australia and southern Africa. These dinosaurs varied enormously in size and sometimes in anatomical features: the above-mentioned Microraptor weighed only a few pounds and had four feathered proto-wings, while the fierce, one-ton Utahraptor could have whomped a Deinonychus with one claw tied behind its back. In between were standard-issue raptors like Dromaeosaurus and Saurornitholestes, swift, fierce, feathered predators that made quick meals out of lizards, bugs, and smaller dinosaurs.
As mentioned above, even the brainiest raptor couldn't hope to outwit a Siamese cat, much less a full-grown human being. However, it's clear that dromaeosaurs (and, for that matter, all theropods) must have been slightly smarter than the herbivorous dinosaurs they preyed on, since the tools required for active predation (a sharp sense of smell and sight, quick reflexes, hand-eye coordination, etc.) require a relatively large amount of grey matter. (As for those lumbering sauropods and ornithopods, they only had to be slightly smarter than the vegetation they munched on!)
The debate about whether raptors hunted in packs has yet to be settled conclusively. The fact is, very few modern birds engage in cooperative hunting, and since birds are tens of millions of years farther down the evolutionary line than raptors, that can be taken as evidence that Velociraptor packs are a figment of Hollywood producers' imaginations. Still, the recent discovery of multiple raptor trackmarks in the same location shows that at least some of these dinosaurs must have roamed in small packs, so cooperative hunting would certainly have been within the realm of possibility, at least for some genera.
A recent study has concluded that raptors--and many other small- to medium-sized theropod dinosaurs--most likely hunted at night, as evidenced by their larger-than-usual eyes. Bigger eyes allow a predator to gather in more available light, making it easier to home in on small, quivering dinosaurs, lizards, birds and mammals in near-dark conditions.
Here's a list of the most notable raptors; just click on the links for more information.
Achillobator This fierce raptor was discovered in modern-day Mongolia.
Adasaurus This raptor's hind claws were unusually small.
Balaur This "stocky dragon" was recently discovered in Romania.
Bambiraptor Yes, this tiny raptor was named after you-know-who.
Buitreraptor The oldest raptor ever discovered in South America.
Changyuraptor Was this feathered dinosaur capable of flight?
Cryptovolans Was this the same dinosaur as Microraptor?
Deinonychus One of the most fearsome predators of the Cretaceous era.
Dromaeosauroides The only dinosaur ever to be discovered in Denmark.
Dromaeosaurus This "running lizard" was probably covered with feathers.
Graciliraptor This tiny dino-bird was a close relative of Microraptor.
Linheraptor This central Asian raptor was "diagnosed" in 2010.
Luanchuanraptor A small, poorly understood Asian raptor.
Microraptor This tiny proto-bird had four wings rather than two.
Neuquenraptor It may actually be a species (or specimen) of Unenlagia.
Nuthetes This raptor was named after the modern monitor lizard.
Ornithodesmus This mysterious raptor was once thought to be a pterosaur.
Pamparaptor This raptor was discovered in the Argentinian Pampas.
Pyroraptor This "fire thief" prowled the plains of prehistoric France.
Rahonavis Was it a raptor-like bird, or a bird-like raptor?
Saurornitholestes A close cousin of Velociraptor.
Unenlagia This bird-like raptor was native to South America.
Utahraptor Probably the biggest raptor that ever lived.
Variraptor The first raptor ever to be discovered in France.Velociraptor This dinosaur was vicious--but a lot smaller than you thought.