Hyaenodon


Hyaenodon is the type genus of the Hyaenodontidae, a family of extinct carnivorous fossil mammals from Eurasia, North America, and Africa, with species existing temporally from the Eocene until the middle Miocene, existing for about.
The various species of Hyaenodon competed with each other and with other hyaenodont genera, and played important roles as predators in ecological communities as late as the Miocene in Africa and Asia and preyed on a variety of prey species such as primitive horses like Mesohippus and early camels. Species of Hyaenodon have been shown to have successfully preyed on other large carnivores of their time, including a nimravid, according to analysis of tooth puncture marks on a fossil Dinictis skull found in North Dakota.

Description

Some species of this genus were among the largest terrestrial carnivorous mammals of their time; others were only of the size of a marten. Remains of many species are known from North America, Europe, and Asia.
Typical of early carnivorous mammals, individuals of Hyaenodon had a very massive skull, but only a small brain. The skull is long with a narrow snout - much larger in relation to the length of the skull than in canine carnivores, for instance. The neck was shorter than the skull, while the body was long and robust and terminated in a long tail.
The average weight of adult or subadult H. horridus, the largest North American species, is estimated to about and may not have exceeded. H. gigas, the largest Hyaenodon species, was much larger, being and around. H. crucians from the early Oligocene of North America is estimated to only. H. microdon and H. mustelinus from the late Eocene of North America were even smaller and weighed probably about.
Compared to the generally larger Hyainailouros, the dentition of Hyaenodon was geared more towards shearing meat and less towards bone crushing.

Tooth eruption

Studies on juvenile Hyaenodon specimens show that the animal had a very unusual system of tooth replacement. Juveniles took about 3–4 years to complete the final stage of eruption, implying a long adolescent phase. In North American forms, the first upper premolar erupts before the first upper molar, while European forms show an earlier eruption of the first upper molar.

Range and species

In North America the last Hyaenodon, in the form of H. brevirostris, disappeared in the late Oligocene. In Europe, they had already vanished earlier in the Oligocene.