Before lions and wolves, these bizarre predators ruled the world for millions of years.

Nature · Published 3 October 2026 Swipe more like this →

In short: Hyaenodonts were once the dominant mammalian carnivores across Africa, Eurasia, and North America. With up to three pairs of shearing teeth and a long, slow adolescence, these predators occupied diverse niches—from forest-dwelling insectivores to massive, bone-crushing hunters—until their eventual extinction roughly 7.5 million years ago.

Hyaenodonta, a group of placental mammals, emerged either in the Late Cretaceous or Early Paleocene. Unlike modern carnivorans, which possess a single pair of carnassial teeth, hyaenodonts evolved up to three sequential pairs of these shearing blades. Their anatomy, characterized by high sagittal crests for powerful jaw muscles and a keen sense of smell, suggests they were specialized for shearing flesh rather than crushing bone, though some species exhibited osteophagous adaptations.

The order's evolutionary history was marked by significant environmental shifts. During the Eocene, they thrived as the primary predators in Europe and Africa. However, the Eocene-Oligocene extinction event triggered a global transition toward an icehouse climate, leading to the expansion of open landscapes. This shift, coupled with the decline of large browsing herbivores like brontotheres, placed hyaenodonts at a disadvantage. Their relatively short limbs made them less efficient than emerging cursorial carnivorans in these new, open environments.

While experts long attributed the hyaenodont decline to direct competition with carnivorans, recent research challenges this narrative. Studies in North America and Europe indicate that hyaenodonts often occupied distinct ecological niches, with little overlap between the two groups. Instead, evidence points toward climatic cooling and the loss of preferred prey as the primary drivers of their terminal decline. By the Late Miocene, the order was reduced to a few lineages, with the final hyaenodont, Dissopsalis, vanishing approximately 7.5 million years ago.

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