"Protobird" is an informal term that has been used by some paleontologists when discussing animals that, while technically classified as non-avian dinosaurs, possess many features normally associated with birds. All protobirds are extinct. 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.