Enantiornithes

Abstract

If you find a bird bone in deposits from the Cretaceous period (145-66 million years ago), chances are it will belong to an enantiornithine bird. This extinct group of birds was mostly arboreal and dominated terrestrial environments from 130 to 66 million years ago. With approximately 90 known genera, they account for more than half of the known diversity of Mesozoic birds. Yet, despite apparently out-competing birds more closely related to living species in most Cretaceous continental environments, enantiornithines mysteriously went extinct at the end of the Cretaceous, alongside all other non-neornithine (crown-bird) dinosaurs.