By Federico L. Agnolín, Fernando E. Novas (auth.)
Although consensus exists between researchers that birds advanced from coelurosaurian theropods, paleontologists nonetheless debate the identity of the gang of coelurosaurians that almost all heavily techniques the typical ancestor of birds. The final twenty years witnessed the invention of a wide range of avian-like theropods that has significantly amplified the anatomical disparity between deinonychosaurians, a few of which resemble Archaeopteryx greater than Deinonychus. between those newly found theropods that convey impressive bird-like features are the four-winged theropods Microraptor and Anchiornis, and the unenlagiids Unenlagia, Buitreraptor, and Rahonavis. A extraordinary team of minute-sized coelurosaurs, the Scansoriopterygidae, additionally indicates a few avian similarities that lead a few authors to interpret them as extra heavily concerning birds than different dinosaurs. With the purpose to discover the phylogenetic relationships of those coelurosaurians and birds, we merged lately released integrative databases, leading to major adjustments within the topological distribution of taxa inside Paraves. We current facts that Dromaeosauridae, Microraptoria, Unenlagiidae, and Anchiornis + Xiaotingia shape successive sister taxa of Aves, and that the Scansoriopterygidae are basal coelurosaurians no longer heavily with regards to birds. the results within the evolutionary series of anatomical characters resulting in birds, together with the starting place of flight, also are thought of in mild of this new phylogenetic hypothesis.
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Extra info for Avian Ancestors: A Review of the Phylogenetic Relationships of the Theropods Unenlagiidae, Microraptoria, Anchiornis and Scansoriopterygidae
In this way, we opt to use another name for the more inclusive clade that includes Pygostylia and Sapeornis. Avebrevicaudans lack the hyperextensible pedal digit II, present in most paravians, including basal birds, and once considered as diagnostic of Deinonychosauria (Gauthier’s 1986). By contrast, the reduction of ungual and preungual phalanges of pedal digit II is considered here as diagnostic of the clade (character 201-0). 11 Selected avebrevicaudans. a, b, Sapeornis chaoyangensis (IVPP V 13275), a mainslab of the most complete Sapeornis skeleton, b detail of reduced tail with pygostyle-like terminal vertebrae.
Peabody Museum of Natural History, Yale University, New Haven, pp 49–68 Norell MA, Makovicky PJ, Clark JM (2000) A new troodontid from Ukhaa Tolgod, Late Cretaceous, Mongolia. J Vert Paleontol 20:7–11 Novas FE (1999) Dinosaur. McGraw-Hill Yearbook of Science & Technology, pp 133–135 Novas FE (2004) Avian traits in the ilium of Unenlagia comahuensis (Maniraptora, Avialae). In: Currie PJ, Koppelhus EB, Shugar MA, Wright JL (eds) Feathered dragons: studies on the transition from dinosaurs to birds.
Following the phylogenetic definition of Sereno (1997), we define Ornithurae as all avialans closer to Aves than to Archaeopteryx. Synapomorphies. 110 (1), 335(1), 371(1), 382(1), 401(1). Content. This node includes Rahonavis + Avebrevicauda. Comments. In this chapter we use the term Ornithurae as originally proposed by Gauthier’s (1986), and later modified by Sereno (1997, 1999), rather than the definition by Chiappe (2001; see also Padian et al. 1999) because Gauthier's definition has priority.