Euornithes (“true birds”) is surely a euphonious taxon as it has been erected independently at least four times within birds. Cope (1889), apparently first to erect the taxon, designated it an order that included what may be regarded as a motley assemblage of birds: gulls, bustards, seriemas, trumpeters, cranes, plovers, sunbitterns, seedsnipes, rails and others. Few ornithologists, as a result, ever adopted the taxon, the original contents of which are spread across Neognathae on a recent morphology-based phylogeny (Mayr and Clarke 2003).
In a Handbook on Zoology, Dementjev (1940) used Euornithes as a higher taxon within Aves. This second taxonomic coming may have gone unnoticed were it not for Kurochkin’s (1996) citation and reformulation of the taxon as Euornithiformes for a completely different purpose: an assemblage of enantiornithine birds with no apparent justification on the basis of character evidence (Sereno 2001). Euornithes may have come to Kurochkin’s attention via Sanz and Buscalioni (1992:840), who erected the taxon a third time for “a sister group of Archaeopteryx”, a role that presumably was fulfilled by the properly defined Ornithurae (Gauthier 1986). No definition beyond those words was given (despite various on-line commentary), and so it is not clear where this taxon would now be positioned. It could be equivalent to Ornithurae sensu Gauthier 1986 or Ornithothoraces (Chiappe 1995), both of which have been properly defined.
Unaware of Sanz and Buscalioni (1992), Sereno (1998) erected Euornithes a fourth (and one can hope) final time as a stem-based taxon defined as “all ornithothoracines closer to Neornithes than to Sinornis.” The taxon is properly attributed to Cope (1889), and the active definition is a first-order revision of that in Sereno (1998) that uses species (Sinornis santensis, Passer domesticus) as specifiers. Euornithes, so defined, joins a node-stem triplet (with Ornithothoraces and Enantiornithes) that marks one of the most profound dichotomies in early avian diversification. As the fossil record of non-enantiornithine birds from the Cretaceous improves, Euornithes will prove to be a most useful taxon.
Chiappe et al. (1999:3) coined Ornithuromorpha in the abstract of a monograph on Confuciusornis; he neither discussed it further in the text nor proposed a definition. Chiappe (2001:126) provided a node-based definition using Patagopteryx, Vorona, and Ornithurae as specifiers. Because he regarded all of these taxa as closer to Neornithes than to Enantiornithes, this new taxon has the same taxonomic content as Euornithes. Ornithuromorpha, nevertheless, is not a junior synonym of Euornithes, because the former is node-based and the latter stem-based. More recently Chiappe (2002:457) dropped Vorona from the definition presumably because this incompletely known taxon is positioned within Enantiornithes in some analyses. If Vorona is placed within Enantiornithes, then Ornithuromorpha would constitute a junior synonym of Ornithothoraces. The current utility of Ornithuromorpha is questionable.