This is the largest member of a group of very successful and intimidating predators.

Meaning of scientific name
"hyena-toothed".

Pronunciation of scientific name
hi-EE-noh-don

Statistics
The different Hyaenodon species ranged from 30cm to 1.4m at the shoulder. Hyaenodon gigas is the largest.

Physical description
There were many species of Hyaenodon in the Oligocene, as they were the dominant predators of the time. Some were small and rather fox-like but others were huge rhino-sized running predators with enormously powerful jaws.

Distribution
Hyaenodon fossils are common in the Hsanda Gol formation of Mongolia, and are also found in North America.

Habitat
They lived on the grassless scrubby plains of Asia and North America.

Diet
They were carnivorous - the top hunters of their time.

Behaviour
These very successful predators are part of a group known as Creodonts. The smaller species would have been the lions of the plains . hunting in packs, most often at night, and using their powerful jaws to crush bones, while the largest would probably have hunted alone. The males show grinding marks on their teeth very like modern animals that use the noise of grinding teeth as an intimidation display, and fossilised dung shows that they often defecated on carcasses to protect them from scavengers.

Conservation status
Extinct.

History
They lived 41-25 million years ago. The early Hyaenodons were fox-like animals in the forests, but they took well to the plains when they started to open up, and became the first fast-running predators. The Creodonts gradually became extinct, though - maybe through competition with another group - the Carnivora, which our modern 'true carnivores' belong to.

Best place to see
New Walk Museum; Sedgwick Museum of Earth Sciences

Closest relative
The Creodonts became extinct (although they are thought to be related to the modern carnivores).