Birds are Dinosaurs: Simple Answer to a Complex Problem

Abstract

Richard Prum's (2002) rancorous, unreviewed essay on the theropod origin of is a one-sided view of a difficult problem, full of anatomical misconceptions that are highly misleading, and advocates that (p. 13), is time to abandon debate on the theropod origin of birds. His article is essentially a restatement and defense of a current dogma of paleontology-that are living dinosaurs, directly descended from, or having shared common ancestry with, one of the most highly derived and specialized groups of Cretaceous theropods, the dromaeosaurs (and Cretaceous troodontids), that are presumed to have had ghost lineages going back into the Jurassic Period. Advocates on both sides of the debate agree that are related to dinosaurs, but opponents of the birds-are-dinosaurs movement, including myself, advocate a common shared ancestry of and from basal archosaurs, with less specialized anatomical baggage, at a much earlier time. The are living dinosaurs hypothesis dates back almost three decades to when John Ostrom (see Ostrom 1976), combining studies of his earlier discovery of the late, early Cretaceous dromaeosaur Deinonychus with his speculations on hot-blooded (endothermic) dinosaurs, presented his new dinosarurian origin of theory. At its inception, all theropods were highly energized, endothermic reptiles (endothermic homeotherms), and the smaller theropods had acquired feathers for insulation. Archaeopteryx was an earthbound feathered theropod that could not fly (Bakker 1975) but later learned to fly from the ground up (Ostrom 1979). At that time, the dinosaurian origin of had, of course, nothing to do with cladistic theory, but was based on the overall similarity of Deinonychus to Archaeopteryx. By 1978, Archaeopteryx was said to support two theories: warm-bloodedness in and dinosaurian ancestry of birds (Ostrom 1978:168). I wrote the first rebuttal to hot-blooded (Feduccia 1973), and a mountain of evidence has been marshaled against endothermy in during the last three decades (Morell 1996). Nevertheless, Ostrom (1976) reconstructed the Archaeopteryx skeleton to closely resemble that of the known theropods; it was a terrestrial predator, and