dinosaurs in their time

A large, herbivorous quadruped, Camarasaurus was among the most common of the giant sauropod dinosaurs found in the Jurassic Period in North America. With a name that means “chambered lizard,” this dinosaur was named for its partly hollow vertebrae, and reached up to a massive 60 feet in length.

Camarasaurus lived during the Late Jurassic, some 145 to 150 million years ago, and featured a long, thick neck which made its head appear small in comparison. It had sturdy, spoon-shaped teeth, indicating its diet probably differed from other large herbivores that lived in the same ancient environment, with Camarasaurus most likely feeding on coarser plant materials.

Real fossils of both an adult and a juvenile Camarasaurus discovered at Dinosaur National Monument in Utah are on view in the Dinosaurs in Their Time exhibition at Carnegie Museum of Natural History. The juvenile is represented by a nearly complete skeleton that includes a full skull and even ear bones. The skeleton is displayed with its right side still mostly enveloped in sandstone belonging to a rock unit called the Morrison Formation.

Camptosaurus aphanoecetes, which means “flexible lizard hiding in plain sight,” was a medium-sized plant-eating dinosaur that lived about 145–150 million years ago during the late Jurassic Period. Remains of Camptosaurus have been found in North America and, according to some paleontologists, in England as well. Although the Camptosaurus skeleton on display at Carnegie Museum of Natural History was discovered in 1922, it wasn’t studied in detail until relatively recently.

On exhibit in Pittsburgh for more than six decades, still half buried in Jurassic sandstone, the skeleton was fully removed from the rock in 2005–2006 to transform it into a three-dimensional mount. After the specimen was completely unearthed, it was discovered to show differences with fossils of the dinosaur species it was long thought to represent, Camptosaurus dispar. So, in 2008, the skeleton was established as the type, or name-bearing, specimen of the new species Camptosaurus aphanoecetes by scientists Kenneth Carpenter and
Yvonne Wilson.

This Camptosaurus skeleton was excavated by Earl Douglass and his field crew from rocks belonging to the Morrison Formation in the Carnegie Quarry at Dinosaur National Monument in Utah. Today it is on display at Carnegie Museum of Natural History.

Unlike many herbivores of its time, Dryosaurus altus was not very large. Standing four feet high at the hips and growing up to 11 feet in length, Dryosaurus may have weighed only 200 pounds. But this bipedal dinosaur was fast. It had long, powerful hind legs that carried it through the Late Jurassic wilderness, providing its primary defense against predators.

With a name that means “tall oak tree lizard,” Dryosaurus had short front limbs and a long tail that may have been used as a counterbalance. It had a beak for cropping vegetation and was most likely an efficient chewer, with strong teeth and a hinged jaw. This hinge allowed the herbivore to slide its upper and lower jaws past one another as it chewed, an unusually advanced feeding adaptation for this time period.

One of the oldest known members of the dinosaur group Ornithopoda, Dryosaurus fossils have been found in the western United States and possibly eastern Africa (though some paleontologists think the African fossils belong instead to a close relative called Dysalotosaurus). The specimen on display at Carnegie Museum of Natural History was discovered in 1910 by Earl Douglass and his field crew in the Morrison Formation at what is now Dinosaur National Monument in Utah.