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Phylogenetic position of the enigmatic Tertiary avian family Zygodactylidae
SVPCA Conference
Platform presentation (20 minutes)
*Nikita V Zelenkov
The avian genus Zygodactylus was described on the basis of isolated distal tarsometatrsi from the Miocene of Germany and France. The tarsometatarsus of this genus displays a distinctive feature characteristic of all obligatory zygodactyl birds (i.e. birds with the retroverted outer toe) namely the large accessorial trochlea for the fourth toe. Such a structure can be found only in Psittaciformes (parrots) and Pici (woodpeckers and allies) but Zygodactylus cannot be referred to neither. Surprisingly, recently discovered new specimen of Zygodactylus from the late Oligocene of France (Mayr, 2008) shows the great similarity with the Eocene birds Primoscenidae, which were also zygodactyl. Cladistic analysis placed Zygodactylidae (taxon uniting “Primoscenidae” and Zygodactylus) as a sister group of Passeriformes, the largest recent avian order all members of which possess anysodactyl foot (with only first toe pointing backward). Such stable foot morphology in all passerine birds raises the question if such a systematic position of Zygodactylidae correct. Comparison of Zygodactylidae with the both Passeriformes and Piciformes shows that there are only a few characters distinguishing Zygodactylidae from Piciformes. The obvious question is thus what is more important – foot structure which for a long time played a great role in avian systematics or a few other characters. Functional analysis of the features distinguishing Zygodactylidae from Pici and Passeriformes allows for inferring the evolutionary and systematic weight of these characters and thus for evaluating the relationships of this enigmatic avian taxon. The work is supported by grants from RFFI (? 07-04-00360) and Leading Scientific School (NSh – 6228.2006.4).
London 2020