T.D. Jones, J.A. Ruben, L.D. Martin, E.N. Kurochkin, A.Feduccia, P.F.A. Maderson, W.J. Hillenius, N.R. Geist, V. Alifanov.  2000.  Science 288:2202-2205.

Abstract: Longisquama insignis was an unusual archosaur from the Late Triassic of central Asia. Along its dorsal axis, Longisquama bore a series of paired integumentary appendages that resembled avian feathers in many details, especially the anatomy of the basal region. The latter is sufficiently similar to the calamus of modern feathers that each probably represents the culmination of virtually identical morphogenetic processes. The exact relationship of Longisquama to birds is uncertain. Nevertheless, we interpret Longisquama's elongate integumentary appendages as non-avian feathers and suggest that they are probably homologous with avian feathers. If so, they antedate the feathers of Archaeopteryx, the first known bird from the Late Jurassic.