>>13958322No, big dinosaurs at the end of the Cretaceous period went extinct, small dinosaurs, also known as avian dinosaurs, evolved over time into modern birds. Birds are dinosaurs, just avian dinosaurs.
>how do we know they're relatedSkeletal structure and genetic evidence. Within dinosaur skeletons of the chest area we can find space for air sacks, which is a thing that helps birds breathe during flight, and helped dinosaurs with their massive sized. Hip placement, general skeletal structure, and the shape of vertebrae are also a big indicator. You can also see how a chicken's wing, for example, is a modified claw. It's very fascinating honestly.
