Archaeopteryx (1861)
A fossil from Germany showed a reptile-like skeleton with fully modern flight feathers, the first recognized transitional fossil between non-avian dinosaurs and birds.
Archaeopteryx became a key piece of evidence for evolution, examined by Darwin and Huxley.
It established the deep time of feather evolution and the utility of feathers as a diagnostic trait for the bird lineage.
Just as Archaeopteryx bridged dinosaurs and birds, understanding hesperornithiform feather structure bridges the gap between primitive dinosaur coverings and modern bird plumage.
