Pubis
The earliest birds and theropod dinosaurs have a small boot-shape at the end of the pubis. Other dinosaurs don’t have this.
Wrist
Hang on, birds have wrists? Yes, like us, birds have wrists, elbows and shoulders.
Birds have flexible wrists that let them fold their wings when they rest. This flexibility first evolved among the theropod dinosaurs.
Tail
The last few vertebrae of a bird’s tail are fused together. This is called the pygostyle. It supports the bird’s tail feathers. You can see this in many theropod dinosaurs too.
Hollow bones
The bones of birds and theropod dinosaurs are hollow, with thin walls and spaces filled with air.
Beak
Everyone knows birds have beaks. But did you know many dinosaurs had them too?
Posture
Scientists know that dinosaurs walked in an upright posture. This means their legs were under their bodies, not sticking out to the side like a crocodile’s. Birds also walk in an upright stance.
Illustration/animation: Chris Edser
Wing
The bones and muscles in the arms and chest of birds and theropod dinosaurs are very similar. Theropod dinosaurs could move their arms in the up and down motion that allows a bird to flap its wings.
Clockwise from top left: Flamingo, Wedgetailed Eagle (Bunjil), Hornbill, Macaw, Peacock. Illustration/animation: Chris Edser
Wishbone
You might know that birds have a bone known as the wishbone. Scientists call it the furcula.
The discovery of a wishbone in theropod dinosaurs was a big step in understanding the relationship between birds and dinosaurs. Even T.rex has one!
Feathers
Not all dinosaurs had feathers. But we know from fossils that the theropod dinosaurs did.
Early theropod feathers weren’t used for flying, but they were probably useful for keeping warm—and looking cool!
