HYENODON:THE RAZOR-JAWS

Hyaenodon ("hyaena-toothed") is an extinct genus of Hyaenodonts, a group of carnivorous creodonts of the family Hyaenodontidae endemic to all continents except South America, Australia and Antarctica, living from 42—15.9 mya, existing for approximately 26.1 million years.

Some species of this genus were amongst the largest terrestrial carnivorous mammals of their time; others were only of the size of a marten. Hyaenodon was one of the latest genera of the Hyaenodonts and is known from the Late Eocene to Early Miocene. Remains of many species are known from North America, Europe, Asia and Africa (In 1993 42 species were distinguished).

Typical of early carnivorous mammals, the Hyaenodon had a very massive skull but only a small brain. 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. Despite the name, these creatures are not related to hyenas.

The average weight of adult or subadult H. horridus, the largest North American species, is estimated to about 40 kilograms (88 lb) and may not have exceeded 60 kilograms (130 lb). H. gigas, the largest Hyaenodon species was much larger, being 500 kilograms (1,100 lb) and around 10 feet. H. crucians from the early Oligocene of North America is estimated to only 10 to 25 kilograms (22 to 55 lb). H. microdon and H. mustelinus from the late Eocene of North America were even smaller and weighed probably about 5 kilograms (11 lb).

In North America the last Hyaenodon disappeared along with species like H. brevirostris in the late Oligocene. In Europe they had already vanished earlier in the Oligocene. From the Miocene in Africa there are three species (H. andrewsi, H. matthewi and H. pilgrimi) known, but none of these reached the dimensions of Asian species like H. gigas and H. weilini