Hyaenodon

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Hyaenodon
Fossil range: Late Eocene to Early Miocene

Skull of Hyaenodon cayluxi, Muséum national d'Histoire naturelle, Paris.

Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Creodonta
Family:	Hyaenodontidae
Genus:	Hyaenodon Leidy, 1869

Species ^[1]

H. bavaricus
H. brevirostris
H. chunkhtensis
H. crucians
H. eminus
H. exicuus
H. gigas
H. horridus
H. incertus
H. leptorhynchus
H. megaloides
H. microdon
H. milloquensis
H. mongoliensis
H. montanus
H. mustelinus
H. pervagus
H. raineyi
H. venturae
H. vetus
H. weilini
H. yuanchensis

Hyaenodon ("hyaena-toothed") is an extinct genus of Hyaenodonts, a group of Creodonts. Some species of this genus were amongst the largest terrestrial carnivorous mammals.

These highly specialised predators appeared in the Late Eocene 41 million years ago existing through the Oligocene Epoch until 21 million years ago.^[2] Their long and narrow jaws were powerful and suitable for biting and crushing. Typical of early mammals, they had very massive skulls but only small brains.^{[citation needed]} It had a long skull with a narrow snout - much larger in relation to the length of the skull than in canine carnivores, for instance. Its neck was shorter than its skull, while its body was long and robust and terminated in a long tail. It had five toes on both its fore and hind feet, the first of which was shorter than the rest.^{[citation needed]}

Reconstruction by Heinrich Harder, c.1920 (Note artist's error: The subject is shown with digitigrade feet, like a wolf. Hyaenodon may actually have had plantigrade bones.)

The structure of their skulls suggests that they had an acute sense of smell. Some species may have been specialized scavengers, but many were clearly active predators.^{[citation needed]} Hyaenodon resembled a Recent hyena in appearance, but its much sharper teeth and well developed sectorials (carnassials) show that it had a very different diet. Hyaenodon did not live on carrion, but hunted ungulates up to the size of a sheep.^{[citation needed]}

Hyaenodon gigas, the largest Hyaenodon species was as much as 1.4 m high at the shoulder and 10 feet long. It weighed about 500 kg.^{[citation needed]} In other words, it was as large as an average modern horse.

In contrast, the smallest species were only 30 cm high at the shoulder.^[2]

Fossils of Hyaenodon species have been found in Asia, North America, Europe, and Africa.^{[citation needed]}

Hyaenodon was a very successful and diverse genus, but eventually the modern carnivorous mammals of the order Carnivora were able to outcompete them. The genus was almost extinct by the end of the Paleogene.^[2]