Hadrosaurus (Greek for "sturdy lizard"); pronounced HAY-dro-SORE-us


Woodlands of North America

Historical Period:

Late Cretaceous (80-75 million years ago)

Size and Weight:

About 30 feet long and 3-4 tons



Distinguishing Characteristics:

Large size; broad, flat beak; occasional bipedal posture

About Hadrosaurus

Like many discoveries from the 1800s, Hadrosaurus is simultaneously a very important and a very obscure dinosaur.

It was the first near-complete dinosaur skeleton ever to be discovered in North America (in 1858, in Haddonfield, New Jersey, of all places), and it has given its name to an extremely populous family of herbivores--the hadrosaurs, or duck-billed dinosaurs. Celebrating this history, New Jersey named Hadrosaurus its official state dinosaur in 1991, and the "sturdy lizard" is frequently invoked in attempts to pump up the Garden State's paleontology pride.

However, as far as duck-billed dinosaurs are concerned, Hadrosaurus itself occupies the far fringes of paleontology. To date, no one has discovered this dinosaur's skull--the type fossil, named by the famous American paleontologist Joseph Leidy, consists of four limbs, a pelvis, bits of the jaw, and over two dozen vertebrae--so recreations are based on the skulls of similar genera, such as Gryposaurus. To date, Hadrosaurus appears to be the only member of its genus (the only named species is H. foulkii), prompting some paleontologists to speculate that it may really be a species (or specimen) of another genus of hadrosaur.

(By the way, in 1868, the Hadrosaurus at the Philadelphia Academy of Natural Sciences was the first dinosaur skeleton ever to be displayed to the general public.)

Given all this uncertainty, it has proven rather difficult to assign Hadrosaurus to its proper place on the hadrosaur family tree. This dinosaur was once honored with its own sub-family, the hadrosaurinae, to which better-known (and more highly ornamented) duck-billed dinosaurs like Lambeosaurus were once assigned.

Today, though, Hadrosaurus occupies a lonely branch on cladistic diagrams, removed from such familiar genera as Maiasaura, Edmontosaurus and Shantungosaurus, and not many paleontologists reference it in their publications.

But enough about classification; what was Hadrosaurus actually like? This was a robustly built herbivore, measuring about 30 feet from head to tail and weighing up to four tons, and it probably spent most of its time crouched on all fours, chomping on the low-lying vegetation of its late Cretaceous habitat. Like other duck-billed dinosaurs, though, Hadrosaurus would have been capable of rearing up on its two hind legs and running away when startled by hungry tyrannosaurs, which must have been a stressful experience for any smaller dinosaurs lurking nearby!