Archaeopteryx and living birds share many features with reptiles.

In fact, birds share over 100 anatomical features with one particular group of reptiles—dinosaurs!

This suggests that birds evolved from dinosaurs and may therefore be considered a type of dinosaur.

This diagram, called a cladogram, shows us the likely evolutionary relationships between birds and their dinosaur relatives.

Let's use this cladogram to examine the major groups within the dinosaur lineage.