How does taxonomy work? The case of the Avian Dinosaurs
There was a taxonomic revolution brought about by cladistics https://en.wikipedia.org/wiki/Cladistics. Willi Hennig wrote about it in 1950, but he was an East German, and his work did not gain traction in the West until it was translated into English in the late 1960s. Then it took a while to become consensus. Since then, all taxonomy is based on phylogenetic relationships. So for 100 years, we talked about "Reptiles" and knew what they were. Under phylogenetic taxonomy however, once we understood that birds were descended from theropod dinosaurs, nomenclatural rules require that birds ARE dinosaurs. This makes sense, because a Robin is more closely related to a Tyrannosaurus than a Tyrannosaurus is to an Iguanodon. Technically, taxonomy changes with the publication of phylogenies that make formal nomenclatural changes. Once a peer-reviewed paper is published, the names change. But sometimes phylogeny papers are sloppy, or wrong. So for something as major as Avian Dinosaurs, it would generally take more than just one sloppy paper to change consensus. Scientists now consider birds to be Dinosaurs. The public will continue thinking of Dinosaurs without birds. This is a difference between common names and scientific names. Birds are a subgroup of Dinosauria. Consensus depends on whether you are a scientist or not. Scientists now are at a consensus that Birds are derived from theropod dinosaurs, and therefore, ARE dinosaurs. The consensus of the public will lag behind.