Here, we describe a new ecomorph of Nimravidae, Taotienimravus songi gen. et sp. nov., from the middle Oligocene of eastern Asia. Phylogenetic analyses indicate that the new species is closely related to Nimravus and Dinaelurus, and it represents a non-sabertooth ecomorph form with initial bone-cracking adaptation—a unique form among Nimravidae. An increase in body size among Nimravidae appears to have coincided with the demise of Oxyaenidae, another carnivorous clade in the Palaeogene. The initial emergence of macrocarnivorous adaptation of Carnivora by a felid-like ecomorph probably reflects competition dynamics. Nimravidae successfully occupied several ecological niches that were not exploited by Felidae, probably owing to the lack of competition within Carnivora during much of their evolutionary history. Our study underscores the role of both abiotic and biotic factors in shaping niche availability for these animals, emphasizing the need for discussions on niche change and evolution to be grounded in these considerations.