Gryposaurus (Greek for "hook-nosed lizard"); pronounced GRIP-oh-SORE-us


Woodlands of North America

Historical Period:

Late Cretaceous (85-75 million years ago)

Size and Weight:

Up to 40 feet long and five tons



Distinguishing Characteristics:

Long, narrow skull; large bump on nose; occasional bipedal posture

About Gryposaurus

In most ways a typical hadrosaur--or duck-billed dinosaur--of late Cretaceous North America, Gryposaurus was distinguished by the prominent, arched bump on its nose, from which its name {"hook-nosed lizard") derives. As with other such ornately equipped dinosaurs (like the horned, frilled ceratopsians), paleontologists speculate that this feature evolved as a sexually selected characteristic --that is, males with bigger, more prominent noses were more attractive to females during mating season. However, Gryposaurus may also have used its giant schnozz to honk and blare at fellow herd members, o alert them to skulking raptors and tyrannosaurs, and (somewhat less probably) it may even have poked the flanks of these predators with its nose in an attempt to drive them away.

Like other hadrosaurs, the 30-foot-long, two-ton, plant-eating Gryposaurus was similar in behavior to modern bison and buffalo--and the numerous fossil specimens that have been discovered across North America are a strong hint that this duck-billed dinosaur roamed the continent in herds (though whether these herds contained a few dozen, a few hundred, or a few thousand individuals is impossible to say). However, there's one important difference between these ancient hadrosaurs and modern cattle (or wildebeest): when startled by predators, Gryposaurus could run briefly on its two hind legs, which must have made for a comical sight during stampedes!

The name Gryposaurus is often used interchangeably with Kritosaurus, thanks to the confusion surrounding this dinosaur's taxonomic history. The type fossil of Gryposaurus was discovered in Canada's Alberta Province in 1913, and later described and named by the Canadian paleontologist Lawrence Lambe. However, the American fossil hunter Barnum Brown had discovered a similar genus a few years earlier, in New Mexico, which he named Kritosaurus ("separated lizard"). The Gryposaurus skeleton described by Lambe provided additional clues about the proper reconstruction of the Kritosaurus skeleton, and although Brown himself proposed that the two genera should be "synonymized," they have both managed to survive down to the present day. (We won't even mention the suggestion of Jack Horner that both Gryposaurus and Kritosaurus should be synonymized with Hadrosaurus!)

Today, there are three generally accepted species of Gryposaurus. The type species, G. notabilis, is known by about two dozen skulls, as well as two more complete specimens that had originally been assigned to a since-synonymized species, G. incurvimanus. A second species, G. latidens, was discovered in Montana; it's represented by fewer individuals than G. notabilis, the hooked nose of this species was set farther down its snout and its teeth of which were less derived (harking back to those of the much earlier Iguanodon). Finally, there's G. monumentensis, named in 2007 after the discovery of a single individual in Utah. As you may have guessed from its name, this Gryposaurus species was larger than the others, some adults attaining 40 feet in length and weights in the neighborhood of five tons.