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New(ish) paper on polyphyletic Aves (Kurochkin)
I had heard that at least one Russian paleontologist still fervently
believed that birds (and avian flight) evolved twice. I didn't believe it,
until I saw this...
Kurochkin, E.N. (2006). Parallel evolution of theropod dinosaurs and birds.
Zoologicheskii Zhurnal. 85(3): 283-297.
ABSTRACT: "In recent years, the hypothesis of an origin of birds from
theropod dinosaurs has been
widely spread. Direct sisterly relations between theropods and birds are
established based on such casual and formal synapomorphies, as the number of
tail vertebrae, relative length of the humerus,
flatness of the dorsal edge of the pubis, etc. In essence, this hypothesis
is developed on such characters (recognized as homologies), as feathers,
furcula, uncinate processes, pygostyle, double-condyled cranial joint of
quadrate, and inverted back pubic bone, which are discovered in various
groups of Coelurosauria. Not so long ago, they were considered as
apomorphies in birds. Nevertheless, all these characters are mosaically
distributed among dromeosaurids, troodontids, oviraptorosaurids,
therizinosaurids, and tyrannosaurids. There is no Theropoda group, where
they would occur together. This fact testifies to parallelism in the
evolution of theropods and birds. Theropod dinosaurs and Sauriurae
(Archaeornithes with Enantiomithes) have a number of important system
synapomorphies that demonstrate their close relationships. Ornithurine
birds do not have such synapomorphics, but their monophyly is established
according to a great number of diagnostic characters. The hypothesis of
independent origin of Sauriurae and Ornithurae is substantiated. According
to this hypothesis, Sauriurae originated from Theropoda in the Jurassic
period and Ornithurae from basal Archosauromorpha in the Late Triassic one.
Findings of small avian footprints in the upper Triassic and lower Jurassic
deposits on different continents support the existence of birds in the Early
I have to say, I don't know the difference between a "formal" and "casual"
synapomorphy. I guess I'll have to track down the paper and read it to find
BTW, it was Tracy Ford who told me about this idea ('diphyletic Aves') still
being around - so sorry for doubting you, Tracy. I guess the idea is not
quite dead after all. More 'undead', I'd say. It's had enough cladistic
stakes driven through its heart, but on it goes...