Divergences and losses of flight within ratite lineage occurred right after the K-Pg extinction event wiped out all non-avian dinosaurs and large vertebrates 66 million years ago.[6] The immediate evacuation of niches following the mass extinction provided opportunities for Palaeognathes to distribute and occupy novel environments. New ecological influences selectively pressured different taxa to converge on flightless modes of existence by altering them morphologically and behaviorally.