Hall of Saurischian Dinosaurs

Allosaurus fragilis 
(AL-o-SO-rus fra-JIH-lis)
"different reptile” 

With a strong jaw, clawed arms, and sharp, serrated teeth, Allosaurus fragilis is believed to have been a fierce hunter that preyed on a variety of other dinosaurs. It lived 140 million years ago during the Jurassic period, a prime era for species of big dinosaurs.

Today, more than 60 individual Allosaurus specimens have been collected, most in the Morrison Formation of the western US and Canada; as such, paleontologists conclude it was the most common large predatory dinosaur in western North America. Discovered in Aurora, Wyoming, this Allosaurus fragilis specimen was part of the famous collection of Edward Drinker Cope, the eminent naturalist and paleontologist. It is posed feeding on a partial carcass of the sauropod Apatosaurus–an appropriate meal for this most voracious predator. 


Apatosaurus excelsus 
(AP-a-to-SO-rus el-SEL-sus)
"deceptive reptile"

The colossal Apatosaurus excelsus, formerly known as the Brontosaurus, lived 140 million years ago during the Late Jurassic period. It was one of the largest land animals ever to exist and a key member of the long-necked sauropod family. This specimen was collected in the late 1890s in the Como Bluff area of Wyoming. When it went on display in 1905, this specimen was the first sauropod dinosaur ever mounted, and it has been a focal point of the collection ever since. 

To this day, only one Apatosaurus has ever been found with its skull attached. In fact, for several years this mount included a skull from a differing species of dinosaur. Today, a cast of a skull found lying close to an Apatosaurus skeleton now sits on top of this gigantic fossil's neck. Despite its much heavier body and shorter neck, Apatosaurus is very closely related to both Diplodocus and Barosaurus

Albertosaurus libratus 
(al-BUR-to-SO-rus li-BRA-tus)
 "reptile from Alberta” 

Two grand Albertosaurus libratus face one another in this dramatic display. Albertosaurus was a tyrannosaur quite similar to Tyrannosaurus rex, its close relative. It lived 75 million years ago during the Late Cretaceous, about 5 million to 10 million years before the Tyrannosaurus rex

Both Albertosaurus and Tyrannosaurus have only two fingers on the hand and a very large skull, but they differ in the proportions of the hind legs and in overall size, with Tyrannosaurus towering over the smaller Albertosaurus

Initially, famed fossil hunter Barnum Brown identified the smaller of the two specimens in this display as a separate species, but later scientists have suggested that it is a juvenile Albertosaurus libratus. This pair was collected from Red Deer River, in Alberta, Canada in the early 20th century. Today, the area where these skeletons were discovered is known as the Dry Island Albertosaurus Bonebed, in recognition of the many Albertosaurus specimens found there. 


Tyrannosaurus rex 
(tih-RAN-o-SO-rus reks)
"tyrant reptile" 

One of the Museum’s most iconic displays, this Tyrannosaurus rex skeleton mount and Tyrannosaurus rex skull draw countless visitors eager to come face to face with evolution’s greatest predator. Tyrannosaurus rex, the largest and most fearsome carnivore of all time, lived 65 million years ago in the Late Cretaceous. 

This imposing skeleton, measuring 40 feet long and 12 feet high, is one of the few authentic specimens of Tyrannosaurus on public display. To the front of the display, housed in glass, is the first complete Tyrannosaurus skull ever collected; to this day, it remains one of the highest quality theropod skulls known to science. Both specimens were collected in 1908 from Big Dry Creek in Montana by master dinosaur hunter Barnum Brown and Peter C. Kaisen, Brown’s assistant. 


Deinonychus antirrhopus 
(di-NON-ih-kus AN-te-RO-pus)
"terrible claw"

Exploring the fascinating relationship between dinosaurs and birds, this diorama features the only real fossil Deinonychus on display in the world. Deinonychus antirrhopus, a non-avian maniraptor that lived 107 million years ago during the Early Cretaceous, was a fearsome predator with sickle claws and sharp teeth. This specimen was collected by paleontologist Barnum Brown and his assistant Peter C. Kaisen in Buster Creek, near Billings, Montana in 1931. 

For paleontologists, Deinonychus has provided many important insights, including a re-evaluation of dinosaurs as nimble, active predators rather than slow, sluggish giants. More significantly, observations of Deinonychus’s light, hollow bones and extremely advanced wrists led to one of the most revolutionary discoveries of twentieth-century paleontology: the dinosaurian origins of birds. 

Barosaurus lentus 
(BAR-o-SO-rus LEN-tus)
 "heavy reptile" 

In this unique display, visitors peer down through a glass walkway to view fossil specimens below from Barosaurus lentus, a dinosaur that lived 140 million years ago during the Late Jurassic. From this perspective, the viewer can appreciate the extreme length—and walk the entire distance—of the Barosaurus neck vertebrae. 

As the length of its neck indicates, Barosaurus lentus was a massive dinosaur, with some specimens measuring more than 85 feet in length and weighing more than 20 metric tons. Not only do the fossils in this display comprise the most complete specimen of a Barosaurus yet discovered, but they also are the same fossils from which the beloved Barosaurus in the Theodore Roosevelt Rotunda was cast. They were collected between 1912 and 1914 from the Dinosaur National Monument in Utah