The first Archaeopteryx fossil was found in Germany in 1861. It was a surprise because no birds were known from so far back. The Archaeopteryx fossil is often called the first bird. But scientists now think there may be older bird ancestors.

Scientists are still debating whether Archaeopteryx could truly fly or only glide.

Birds evolved from small meat-eating dinosaurs called theropods. Theropods were a group of two-legged dinosaurs that included T. rex. Velociraptor had feathers but could not fly.

As of November 2026, Sinosauropteryx was the first non-avian dinosaur found with feather-like structures on its body.

Microraptor was a tiny feathered dinosaur about the size of a crow. Its feathers were probably black and shiny.

In 1877 a schoolteacher found large fossils near Morrison, Colorado. The schoolteacher sent bones to both Othniel Marsh and Edward Cope, two fossil hunters.

The scientist who first described Stegosaurus thought its plates lay flat on its back. Scientists still are not sure why Stegosaurus had its back plates. Ideas include protecting it from predators and helping it control its body heat.

As of November 2026, scientists have debated whether Torosaurus is just the fully grown form of Triceratops. A 2012 study of skulls concluded that they were different species. Brontosaurus was thought to be the same dinosaur as Apatosaurus for about a hundred years. A 2015 study found it was a separate kind.

As of November 2026, the end-Permian mass extinction, before the dinosaurs, was the biggest in Earth's history. The end-Cretaceous one was the second biggest.

Words to know

• glide: float without flapping
• theropods: two-legged hunters
• ancestors: early relatives
• species: a kind