Parallelism and lineage replacement of the late Miocene scimitar-toothed cats from the old and New World

In contrast to large-scale convergence/parallelism, the small-scale convergence/parallelism of sabertooth adaptation within closely related genera and species has been seldom investigated. Here, we describe and analyze the rich material of Nimravides catocopis, and provide evidence using a new phylogenetic analysis that Nimravides was endemic to North America. The late Miocene (10.5-6.5 Ma) Nimravides represents a lineage that shows clearly parallelism with the contemporary Old World lineage of Machairodus-Amphimachairodus.The Old World lineage experienced a higher evolutionary rate of cranial trait than the New World one did. The low density of Amphimachairodus at its first appearance in North America suggests that the derived traits did not provide a direct competitive advantage over Nimravides, but allowed Amphimachairodus to survive the significant faunal change in the early-late Hemphillian (∼6.5 Ma) in North America, a process that probably can be applied to most replacement of closely related lineages.