"Pterodactyl" is the generic word many people use to refer to two famous pterosaurs of the Mesozoic Era, Pteranodon and Pterodactylus. Ironically, these two winged reptiles weren't all that closely related to one another. Below you'll discover 10 essential facts about these so-called "pterodactyls" that every admirer of prehistoric life should know.

01 of 10 There's No Such Thing as a Pterodactyl It's unclear at what point "pterodactyl" became the pop-culture synonym for pterosaurs in general—and for Pterodactylus and Pteranodon in particular—but the fact remains that it's this word most people (especially Hollywood screenwriters) prefer to use. Working paleontologists never use the term "pterodactyl," instead of focusing on individual pterosaur genera, of which there were literally hundreds—and woe to any scientist who confuses Pteranodon with Pterodactylus!

02 of 10 Neither Pterodactylus nor Pteranodon Had Feathers Despite what some people still think, modern birds didn't descend from pterosaurs such as Pterodactylus and Pteranodon, but rather, from the small, two-legged, meat-eating dinosaurs of the Jurassic and Cretaceous periods, many of which were covered with feathers. As far as we know, Pterodactylus and Pteranodon were strictly reptilian in appearance, although there is evidence to suggest that at least some odd pterosaur genera (such as the late Jurassic Sordes) sported hair-like growths.

03 of 10 Pterodactylus Was the First Pterosaur Ever Discovered The "type fossil" of Pterodactylus was discovered in Germany in the late 18th century, well before scientists had a firm understanding of pterosaurs, dinosaurs, or, for that matter, the theory of evolution (which was formulated decades later). Some early naturalists even mistakenly believed—although not after 1830 or so—that Pterodactylus was a kind of bizarre, ocean-dwelling amphibian that used its wings as flippers. As for Pteranodon, its type of fossil was discovered in Kansas in 1870 by famed American paleontologist ​Othniel C. Marsh.

04 of 10 Pteranodon Was Much Bigger Than Pterodactylus The largest species of the Late Cretaceous Pteranodon attained wingspans of up to 30 feet, much larger than any flying birds alive today. By comparison, Pterodactylus, which lived tens of millions of years earlier, was a relative runt. The wingspans of the largest individuals spanned only about eight feet, and most species boasted wingspans of only two to three feet, which is well within the current avian range. There was much less difference in the relative weight of the pterosaurs, however. In order to generate the maximum amount of lift required to fly, both were extremely light.

05 of 10 There Are Dozens of Named Pterodactyus and Pteranodon Species Pterodactylus was unearthed way back in 1784, and Pteranodon in the mid-19th century. As so often happens with such early discoveries, subsequent paleontologists assigned numerous individual species to each of these genera, with the result that the taxonomies of Pterodactylus and Pteranodon are as tangled as a bird's nest. Some species may be genuine, others may turn out to be nomen dubium (Latin for "dubiously named," which paleontologists generally translate as, "utter rubbish") or better assigned to another genus of the pterosaur.

06 of 10 No One Knows How Pteranodon Used Its Skull Crest Besides its size, the most distinctive feature of Pteranodon was its long backward-pointing, but extremely light skull crest, the function of which remains a mystery. Some paleontologists speculate that Pteranodon used this crest as a mid-flight rudder (perhaps it anchored a long flap of skin), while others insist it was strictly a sexually selected characteristic (that is, male Pteranodons with the largest, most elaborate crests were more attractive to females, or vice-versa).

07 of 10 Pteranodon and Pterodactylus Walked on Four Legs One of the major differences between ancient, lizard-skinned pterosaurs and modern, feathered birds is that pterosaurs most likely walked on four legs when they were on land, compared to birds' strictly bipedal postures. How do we know? By various analyses of Pteranodon and Pterodactylus fossilized footprints (as well as those of other pterosaurs) that have been preserved alongside ancient dinosaur track marks of the Mesozoic Era.

08 of 10 Pterodactylus Had Teeth, Pteranodon Didn't Besides their relative sizes, one of the major differences between Pterodactylus and Pteranodon is that the former pterosaur possessed a small number of teeth, while the latter was completely toothless. This fact, combined with Pteranodon's vaguely albatross-like anatomy, has led paleontologists to conclude that the larger pterosaur flew along the seashores of late Cretaceous North America and fed mostly on fish, while Pterodactylus enjoyed a more varied—but less impressively sized–diet.

09 of 10 Male Pteranodons Were Bigger Than Females In relation to its mysterious crest, Pteranodon is believed to have exhibited sexual dimorphism, the males of this genus being significantly larger than the females, or vice-versa. The dominant Pteranodon sex also had a larger, more prominent crest, which may have taken on bright colors during the mating season. As for Pterodactylus, the males and females of this pterosaur were comparably sized, and there's no conclusive evidence for gender-based differentiation.