 The authors restricted the term "bird" to refer only to Aves, which they used to mean only modern ("crown group") birds.Gregory S. Paul used the term "protobird" in a wider sense in 1988, to refer to the extremely bird-like non-avian dinosaurs (Maniraptora), including oviraptorosaurs, troodontids, and dromaeosaurids.Paul speculated that these forms were so bird-like they probably had feathers, an idea later proven by fossil evidence.