bird genus - a genus of birds. 1  Craniata, subphylum Craniata, subphylum Vertebrata, Vertebrata - fishes; amphibians; reptiles; birds; mammals. 2  genus Protoavis - extinct primitive birds of the Triassic period; 70 million years before archaeopteryx. 3  genus Archaeopteryx, genus Archeopteryx - a genus of fossil birds. genus Sinornis - a genus of fossil birds. genus Ibero-mesornis - a genus of fossil bird of the subclass Archaeornithes. genus Archaeornis - a genus of fossil bird. genus Struthio, Struthio - type genus of the Struthionidae: African ostriches.