As anyone following this blog is well aware, dinosaurs did not go completely extinct 65 million years ago. A few small genera were able to survive the mass extinction, and one branch in particular became the Avialae, which we know today as birds. They diversified, colonizing habitats their ancestors had once ruled, but now having to compete with mammals as well, which previously had been primarily underground and nocturnal but now found themselves with a variety of niches to exploit.
While many birds were lightweight and airborne, a few different lineages returned to a shape similar to that of their ancestors - the ratites (ostrich, emu, and their relatives), the Gastornithiformes (large predatory ground-dwelling relatives of ducks), the Secretary Bird, and the seriemas, to name a few. But the most striking in terms of convergent evolution with ancestral dinosaurs were the now-extinct Phorusracidae - massive T-rex-like falcons, including the species pictured above, Titanis walleri. It was an estimated 8 feet tall and 330 lbs, and during the last ice age, it ruled the plains of southern North America, once again forcing the smaller mammals to hide or risk being eaten in one great gulp.