Beta-keratin specific immunological reactivity in feather-like structures of the cretaceous alvarezsaurid, Shuvuuia deserti

We report small fibrous structures associated with a new specimen of Shuvuu ia deserti, which we hypothesize are remnants of feather-like epidermal app endages. Multiple analyses suggest that these structures are epidermally de rived and contain epitopes consistent with beta-keratin, a protein expresse d only in extant "reptiles" and birds. Morphological, microscopic, mass spe ctrometric, and immunohistochemical studies are consistent with the interpr etation that, these structures are related to feathers. These data suggest that proteinaceous components may survive across geological time and suppor t the view that alvarezsaurids (Shuvuuia and its allies) are either a linea ge of birds or are a lineage phylogenetically close to them. (C) 1999 Wiley -Liss, Inc.