How could dangerous dinosaurs possibly have been smart? Pound for pound, they were some of the dumbest creatures ever to roam the planet. However, not all raptors, tyrannosaurs, stegosaurs, and hadrosaurs were equally stupid. Some may even (just barely) have attained a mammalian level of intelligence. On the following slides, you'll find a list of the 10 smartest dinosaurs, based on a combination of their anatomy and their behavior.

01 of 10 Troodon Model of a gray feathered Troodon with red comb on top of its head. Just one of the hundreds of life-size dinosaur models at JuraPark Bałtów Dinosaur Park in Poland. Alina Zienowicz / Wikimedia Commons Troodon, a human-size theropod of the late Cretaceous period, has become the poster lizard for dinosaur intelligence, thanks to a decades-old (and somewhat whimsical) paper by the paleontologist Dale Russell speculating about how this dinosaur might have evolved if it weren't for the K-T extinction event. Judging by its predatory arsenal—big eyes, blazing speed, and stereo vision—Troodon must have possessed an especially big brain, "big" in this context meaning about the size of a modern opossum's (which, for its proportions relative to the rest of its body, still placed Troodon well ahead of other dinosaurs).

02 of 10 Deinonychus Deinonychus skeletal mount at Chicago's Field Museum of Natural History. Jonathan Chen / Wikimedia Commons Despite what you saw in Jurassic Park, Deinonychus wasn't nearly clever enough to turn a doorknob (yes, the so-called velociraptors in Steven Spielberg's movie were actually played by this much bigger raptor, albeit scaled up in size and shorn of their characteristic feathers). But there's convincing circumstantial evidence that Deinonychus must have hunted in packs to bring down the plant-eating dinosaur Tenontosaurus, which would entail a fairly sophisticated level of strategic thinking and communication, and hence a bigger brain.

03 of 10 Compsognathus Model of a striped brown and black Compsognathus, a chicken-size dinosaur at the DinoPark located in Plzeň, Czech Republic. DinoTeam / Wikimedia Commons When it comes to dinosaur intelligence, it's not how big your brain is compared to other reptiles in your size class, but how big your brain is compared to the rest of your body. In this respect, the tiny, chicken-size Compsognathus appears to have been an honor student of the late Jurassic period, perhaps as smart as a very dumb mouse (and yes, in the Mesozoic Era, that was enough to land you in the advanced-placement class). Perhaps Compsognathus evolved its level of smarts to keep up with the gliding Archaeopteryx, the fossils of which were discovered in the same German sediments.

04 of 10 Tyrannosaurus Rex Close-up of a Tyrannosaurus rex head located at the Oxford University Museum of Natural History in England. Ballista / Wikimedia Commons You might not think Tyrannosaurus rex had to be particularly smart to hunt down its food—after all, this was the apex predator of late Cretaceous North America, equipped with huge teeth, powerful legs, and a keen sense of smell. But judging by an analysis of existing skulls, T. rex had a fairly large brain by Mesozoic standards (although today this dinosaur might be outwitted by a newborn kitten). T. rex was certainly equipped with more gray matter than the comparably sized Giganotosaurus, an unusually dim-witted predator of South America.

05 of 10 Oviraptor Model of a grayish, red-spotted Oviraptor, also known as an egg thief. HombreDHojalata / Wikimedia Commons As a general rule, even the dumbest birds alive today are brainier than the smartest dinosaurs (from which, of course, they evolved, possibly multiple times). By this token, the feathered Oviraptor (which was not technically a raptor, by the way) may have been one of the most intelligent dinosaurs of the late Cretaceous period; for instance, it was one of the few theropods smart enough to sit on its own eggs until they hatched. (It was initially believed that Oviraptor filched its eggs from Protoceratops, hence this dinosaur's name, Greek for "egg thief.")

06 of 10 Maiasaura Maiasaura hatchling emerging from its egg. Tim Evanson / Flickr.com It takes a certain amount of intelligence (combined with hard-wired instinct, of course) to migrate in large herds, carve out extensive nesting grounds, and tend to your young after they've hatched. By these standards, Maiasaura, the "good mother lizard," must have been one of the most intelligent hadrosaurs of the late Cretaceous period; Egg Mountain in Montana is a testament to this dinosaur's advanced level of parental care. (Let's not go too far, though; this duck-billed dinosaur had a lot in common with the dim-witted wildebeest, as it was constantly preyed on by the meat-eating theropods of North America.)

07 of 10 Allosaurus An Allosaurus skull at the Oklahoma Museum of Natural History in Norman, Oklahoma. Bob Ainsworth / Wikimedia Commons The late Jurassic Allosaurus wasn't quite as intelligent as T. rex, which appeared on the scene over 50 million years later (paleontologists have discovered numerous Allosaurus skeletons at a single site in Utah; the theory is that these theropods stopped to feast on some herbivorous dinosaurs trapped in the mud and stupidly wound up getting stuck themselves). But as a rule, fast, agile theropods tend to have fairly large brains, and Allosaurus was nothing if not fast and agile, making it the apex predator of its North American environment.

08 of 10 Ornithomimus A couple of Ornithomimus dinosaur models located at the Czech Republic's DinoPark in Vyškov. DinoTeam / Wikimedia Commons The "bird mimic" dinosaurs, of which Ornithomimus was the poster genus, were large, fast, two-legged theropods of the Cretaceous period that resembled (and presumably behaved like) modern ostriches. In fact, extrapolating from the size of its brain cavity relative to the rest of its body, paleontologists believe Ornithomimus may have been nearly as smart as a modern ostrich, which would have made it the Albert Einstein of the Mesozoic Era. (Granted, modern ostriches aren't exactly the smartest animals on the face of the Earth, so draw from that conclusion what you will.)

09 of 10 Tarchia A close-up of the skull of a Tarchia dinosaur. Ghegdoghedo / Wikimedia Commons The only ankylosaur on this list, and for a good reason, Tarchia (Mongolian for "brainy one") was so named because its brain appears to have been a smidgen bigger than those of its fellow armored dinosaurs. Ankylosaurs were spectacularly dumb creatures, though, so what this means is that if Tarchia had studied really hard, it might have had a successful career as a giant paperweight. (It's possible that the paleontologists who named this dinosaur Tarchia were having a bit of fun. They also bestowed the name Saichania, meaning "beautiful one" in Mongolian, on a particularly homely dinosaur.)