Pygostylia
From EvoWiki
Pygostylia sensu Chiappe 2002
This taxon has a most contentious history and its definition remains fairly mutable. Chatterjee (1997, 1998) defined Pygostylia as the common ancestor of Iberomesornis romerali and Neornithes, thus synonymous with Ornithothoraces sensu Chiappe (1996). Therefore, Chatterjee's defintion has been effectively abandoned. Chiappe redefined Pygostylia as the common ancestor of Confuciusornis sanctus and Ornithothoraces and all its descendants. Arguably, this clade might be considered all birds closer to Neornithes than to Archaeopteryx, thus rendering it the most inclusive node within Aves. Pygostylia is delineated on the basis of the following synapomorphies (after Chiappe 2002):
- Hyposphene/hypantrum absent
- Pygostyle present
- Tibiotarsus bears an expanded medial condyle
Chiappe (2002) also advanced the degree of pubic retroversion as potential synapomorphy of pygostylian birds, but I have omitted this character in my analysis due to the homoplastic and plesiomorphic nature of opisthopuby.
References:
- Chatterjee, S. 1997. The Rise of Birds: 225 Million Years of Evolution. Johns Hopkins University Press, Baltimore.
- Chatterjee, S. 1998. The avian status of Protoavis. Archaeopteryx 16: 99-122.
- Chiappe, L. 1996. Late Cretaceous birds of southern South America: anatomy and systematics of Enantiornithes and Patagopteryx deferrariisi. In: Arratia, G. (ed.), Contributions of Southern South America to Vertebrate Paleontology, Muncher Geowissenschaftliche Abhandlungen, Reihe A, Geologie und Palontologie 30. Verlag Dr. Friedrich Pfeil, Munich.
- Chiappe, L. 2002. Basal bird phylogeny problems and solutions. In: Chiappe, L. & Witmer, L. (eds.), Mesozoic Birds: Above the Heads of Dinosaurs, 448-472.
