The basic debate is over thirty years old but both sides draw evidence from recent findings of apparently feathered dinosaurs. For decades Martin asserted that the anatomical similarities between dromaeosaurid dinosaurs and birds were mere convergences, and not credible evidence of a close relationship.
The discovery of the dromaeosaurid Microraptor, a small dinosaur with simple filamentous feathers as well as the long flight feathers characteristic of birds, had major ramifications for the debate about what sort of animal might be the most probable ancestor of birds. Researchers like Padian (1985) had hypothesized a running, terrestrial, dinosaur developing feathers and the ability to flap, and Martin and Feduccia were particularly critical of that idea. But Microraptor was interpreted by Xu et al. (2003) as a small, arboreal, gliding dinosaur, thus going beyond the former terrestrial dinosaur/arboreal archosaur opposition.[2] However, in 2004, in response to Microraptor, Martin proposed that Microraptor is a close relative of birds after all but that it, along with all maniraptoran dinosaurs, were not dinosaurs at all.[3] He proposed what he called a compromise hypothesis that all maniraptorans are instead flightless birds, in a scenario where birds evolved from a Longisquama-like basal archosaur first. Martin credits this hypothesis to Gregory S. Paul, but Paul is a strong advocate of the relationship of dinosaurs and birds, and believes that maniraptorans are dinosaurs.[4]
Moreover, if Olshevsky is correct and Longisquama is an early dinosaur, then it may be an ancestor of Microraptor, Longisquamas feathers could be homologous to those of birds, and all three could be dinosaurs.