A Sunny Day With a Giant

About this drawing

Picture a brachiosaurus in the sun some 150 million years ago, in what is now the American West. Fast-forward to the year 1900, when a team of fossil hunters in western Colorado dug up bones so big they could hardly believe their eyes.

Among those finds was an enormous upper arm bone. Because that arm was so long, the animal got the name Brachiosaurus, meaning arm lizard. Believe it or not, no one has ever found a complete skeleton of this dinosaur, so its size is still partly an educated guess.

The rocks where it turned up belong to the Morrison Formation, layers of ancient stone that stretch across states like Colorado, Utah and Wyoming. Back in the Jurassic, this area was a land of rivers and wide floodplains, home to many other dinosaurs. Today it ranks among the best fossil-hunting spots on the planet.

Rebuilding a dinosaur from a few bones is like doing a jigsaw puzzle with half the pieces missing. Experts compare what they have with similar animals to fill in the gaps. Getting a fossil out of the ground takes patience, too. Workers brush it clean, wrap it in plaster, a bit like a cast on a broken arm, and move it carefully to a museum.

• dinosaurs
• brachiosaurus
• fossils
• paleontology