Information Please's informal guide to the biggest, smallest, fastest, smartest, dumbest, widest, oldest, and most popular dinosaurs.

Tyrannosaurus skeleton. (c) Joe Tucciarone

Largest Dinosaur:

Argentinosaurus hinculensis

Argentinosaurus (c) Joe Tucciarone

Although only the back vertebrae, tibia, a few fragmentary ribs, and the sacrum of this dinosaur have been recovered, paleontologists believe Argentinosaurus is the largest dinosaur of them all.

Largest Carnivore:

Giganotosaurus carolinii

Discovered in 1993 by Rubin Carolini, Giganotosaurus surpassed the long-time record holder Tyrannosaurus (10 - 14 meters; 6 - 7 metric tons). T. rex has in fact been bumped into third place-new excavations of Carcharodontosaurus have indicated that it holds second place among the largest, meat-eating dinosaurs.

Smallest Dinosaur:

Compsognathus longipes

Microceratops , a runner-up in the smallest dinosaur category, was only the size of a rabbit. (c) Joe Tucciarone

The smallest known dinosaur, Compsognathus was about the size of a chicken.

Widest Dinosaur:

Ankylosaurus magniventris

Ankylosaurus (c) Joe Tucciarone

Ankylosaurus was the tank of dinosaurs: low, broad, and heavily armored.

Longest Neck:

Mamenchisaurus

The Mamenchisaurus's neck was 10 meters (33 feet) long.

Fastest:

Ornithomiminee

Resembling an ostrich, this dinosaur was estimated to run at a speed of 40-50 mph.

Smartest:

Troodontids

Troodontids had the largest brain-to-body ratio of all the dinosaurs. They are believed to have been as intelligent as modern-day birds.

Dumbest:

Stegosaurus

Stegosaurus. (c) Joe Tucciarone

The Stegosaurus had a brain the size of a walnut. Its brain was so small it is unable to coordinate the Stegosaurus's movements. These dinosaurs relied on a ganglia–a nerve center or “second brain” located in its hips–to make movement possible. But what the Stegosaurus may have been missing in brains was made up for in brawn-the long, swinging tail was studded with sharp spikes.

Earliest Dinosaur:

Eoraptor lunensis

The earliest known dinosaur was Eoraptor lunensis, who is believed to have lived some 227,000,000 years ago.

First Discovered:

Iguanodon

In 1822 an English woman, Mary Ann Mantell, found a large tooth that was determined to be from a large reptile unlike any previously identified. In 1842, paleontologist Sir Richard Owen named the creature dinosaur, which meant “terrible reptile” — terrible in the sense of awesome or formidable.

Best Defense:

Ankylosaurus

Not only is Ankylosaurus the widest of all dinosaurs, but it's the most heavily armored, with bony plates, studs, and spikes lining its entire back-even its eyelids have spikes. In addition, its tail has a thick knob of bone at the end of it, believed to have been used as a very formidable club against its enemies.

Most Popular:

Tyrannosaurus rex

T. rex (c) Joe Tucciarone

Although not the most ferocious or the largest, the Tyrannosaurus is considered the poster boy for bad reptilian behavior, the ultimate embodiment of the predatory carnivore. T. rex certainly ran the show during the Cretaceous Period; and as the world's favorite dinosaur, this regal beast still rules in the popular imagination.

In recent years, however, T. rex's reputation as a savage carnivore has been tarnished. Some paleontologists have argued that T. rex was not a fearless hunter but merely an ignominious scavenger—putting the creature more in the category of a hyena or vulture than king of the beasts. See news story.

Most All-American:

Allosaurus

Allosaurus (c) Joe Tucciarone

So many dinosaur specimens have been excavated in the United States that any number of species could qualify for the title of Most All-American. Excavation sites such as Morrison and Canon City, Colorado, and Como Bluff, Wyoming, have yielded some of the most important dinosaur discoveries. But our vote goes to the Allosaurus. The original Allosaurus bones were found at the Morrison site in Colorado, and most of the more than sixty other skeletons that have been excavated were found in the United States. A few Allosaurus discoveries in Tanzania and Australia have added an exotic dimension to its character. Considering that some dinosaur species are identified by little more than a tooth or a few vertebrae, the uncovering of such a large number of skeletons of a single species is impressive.

Most Hotly Debated:

Apatosaurus

Apatosaurus (c) Joe Tucciarone

See The Great Dinosaur Hoax.