What is Archosauria?

The most recent common ancestor of birds and crocodiles, and all of their descendants. Archosaurs - the "ruling lizards" - are a group of reptiles that first evolved during the Triassic around 250 million years ago. All dinosaurs fall under the banner "Archosauria" as do several kinds of extinct creatures often mistakingly called dinosaurs, such as the flying pterosaurs. But to qualify for entry a few boxes need to be ticked.

Characteristically, archosaurs must have a window in the skull between the eye-socket and nostril known as the "antorbital fenestrae", a small hole on each side of the lower jaw known as the "mandibular fenestrae", a bony ridge known as the "fourth trochanter" on the rear of the thighbone to anchor muscle, and teeth set in sockets.

Archosaurs began their march to global domination some quarter of a billion years ago, but they are still alive and well, and living all around us in the form of modern crocodiles and birds.