Dinosaur Renaissance - Dinosaur Monophyly

Dinosaur Monophyly

Initially, dinosaurs were thought to be a monophyletic group, comprising animals with a common ancestor not shared by other reptiles. However, Harry Seeley disagreed with this interpretation, and split the Dinosauria into two orders, the Saurischia ("lizard-hipped") and the Ornithischia ("bird-hipped"), which were seen as members of the Archosauria with no special relationship to each other. As such, the Dinosauria was no longer seen as a scientific grouping, and "dinosaur" was reduced to being a popular term, without scientific meaning. This became the standard interpretation throughout much of the twentieth century.

This changed in 1974, when Bakker and Peter Galton published a paper in Nature, arguing that not only were dinosaurs a natural monophyletic group, but that they should be raised to the status of a new class, which would also contain birds. Although initially this revival of dinosaur monophyly was controversial, the idea did gain acceptance, and since the rise of cladistic methodology, it has been nearly universally supported. The raising of the Dinosauria to class rank found less support, perhaps largely due to increasing use of phylogenetic taxonomy among vertebrate palaeontologists, in which ranks are entirely abandoned.