Hyaenodon horridus. Illustration and photo-reconstruction of a Hyaenodon lurking in high grass ready to attack its prey. Hyaenodon horridus (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. It lived from 42-15.9 mya, existing for approximately 26.1 million years. The average weight of adult or sub-adult Hyaenodon horridus, the largest North American species, is estimated to be about 40 kilograms and may not have exceeded 60 kilograms.