<p>The late Eocene to Oligocene interval is traditionally associated with a shift from closed to more open habitats in North America. This time interval also saw the diversification and subsequent extinction of North American nimravids. The drivers of the extinction of this early sabertooth group in North America by the late Oligocene (~26&#xa0;Ma; Arikareean North American Land Mammal Age/NALMA) remain unclear. One possibility is that nimravids were at a competitive disadvantage in open habitats relative to caniform predators, perhaps due to a lack of cursorial adaptations. Here I analyze and compare the hunting types of Eocene and Oligocene predators in correlation with their ecological implications via discriminant function analysis of the shape of the elbow joint. The data show that large cursorial predators decreased and ambush predators increased during the early Oligocene (Orellan and Whitneyan Ages), in part due to the diversification of Nimravidae. An increase in the proportion of cursorial hunting predators only occurred in the Arikareean, eventually leading to the 8-million-year “cat-gap” after the extinction of nimravids. My results indicate that nimravids and contemporary canids had similar elbow morphologies, casting doubt on the idea canids were more cursorial. However, my results comparing predicted amphicyonid and nimravid hunting types could indicate possible support for a competitive advantage for amphicyonids in the Arikareean. Ultimately, sampled carnivore elbow morphologies and diversification appear to indicate that ambush hunting was prevalent in the early Oligocene, and that more cursorial niches appeared as the Oligocene progressed.</p>