|Cast of Mossospondylus eggs and embryo |
Photo from Royal Ontario Museum by Daderot (CC)
|Reconstruction of Protoceratops andrewsi |
AntoninJury (Wikimedia Commons) CC BY-SA 4.0
It is suggested that the relatively long generation times of non-avian dinosaurs put them at a disadvantage in competing with birds, reptiles and mammals during the Cretaceous-Palaeogene transition.