Illustration: Brachychampsa montana reptile

This alligator ancestor, called an alligatoroid, likely fed on ancient turtles. It looked much the same as its modern-day descendents.

Image © National Geographic Society

Fast Facts

Type:
Prehistoric
Diet:
Carnivore
Size:
8 to 10 ft (2.5 to 3 m) long
Protection status:
Extinct
Did you know?
Modern alligators look much the same as their 80-million-year-old ancestors.
Size relative to a 6-ft (2-m) man:
Illustration: Brachychampsa montana compared with adult man

This freshwater, carnivorous reptile is among the very earliest alligatoroids known to science. The first Brachychampsa fossil was discovered in Montana's Hell Creek Formation—an ancient suite of rocks that was laid down near the end of the Cretaceous period. That individual animal lived not so long before the Cretaceous-Tertiary extinction that wiped out many of Earth's species some 65 million years ago.

Brachychampsa had short teeth and a large mouth that packed more power than those of living gators. These oral characteristics suggest that Brachychampsa may have preyed on turtles, which were very common in the Hell Creek fauna.

The first alligator ancestors evolved some 245 million years ago. About 80 million years ago, during the Cretaceous period, crocodilians appeared. This group includes alligatoroids, such as Brachychampsa, as well as their close relatives the crocodiles and caimans.

Many of these ancient animals were survivors of the Cretaceous-Tertiary extinction, though no one knows why they lived when so many others perished.

Modern alligators are still closely related to their ancient ancestors and look much like their relatives did 80 million years ago.

Prehistoric Features

  • Photo: Gully bones

    Digging Up Sea Monsters

    Follow the blog from the Spitsbergen Expedition as they unearth "sea monsters″ from the Upper Jurassic Period 150 million years ago.

  • Image: A bacculite

    Photo Gallery: Sea Monsters

    Get a glimpse of what prehistoric sea creatures may have looked like millions of years ago.

  • Photo: A Dimorphodon flies across the forest in a scene from the movie Flying Monsters 3D

    Flying Monsters 3D

    Could flying monsters have existed? With cutting-edge 3-D filming technology and CGI, Flying Monsters 3D recreates spectacular pterosaurs and brings these giant flying creatures to life.

  • 2565.jpg

    Bizarre Dinosaurs

    A bizarre gallery of Mesozoic monsters prompts John Updike to ask: What has evolution wrought?

Please select a test to run

Animals

The Innovators Project

See more innovators »

From the Magazine

  1. Photo: Two adult preen, Ireland

    Gannets Pictures

    Champion divers but clumsy landers, doting parents but hostile neighbors—northern gannets abound in contradictions.

  2. Photo: Silent Ural owl

    Estonia's Ural Owls

    Photographer Sven Začek provides an intimate view of this large raptor.