All dinosaurs went completely extinct 66 million years ago

Birds are scientifically classified as avian dinosaurs (Aves), descending from theropod dinosaurs through continuous evolution during the Cretaceous period. This relationship is supported by skeletal anatomy, embryology, molecular genetics, and the fossil record, including transitional forms like Archaeopteryx. Therefore, dinosaurs did not go completely extinct, over 10,000 species of living birds represent modern avian dinosaurs. Non-avian dinosaurs (like T. rex and Triceratops) did go extinct at the K-Pg boundary, but dinosaurian lineages persisted.