The nonavian theropod quadrate II: systematic usefulness, major trends and cladistic and phylogenetic morphometrics analyses

Abstract

26The skull-bone quadrate in nonavian theropods is very diverse morphologically 27 alongside the disparity of the group as a whole. However this disparity has been 28 underestimated for taxonomic purposes. In order to evaluate the phylogenetic potential and 29 investigate the evolutionary transformations of the quadrate, we conducted a Catalano-30Goloboff phylogenetic morphometric analysis as well as a cladistic analysis using 98 discrete 31 quadrate related characters. The cladistic analysis provides a fully resolved tree mirroring to 32 some degree the classification of nonavian theropods. 33The quadrate morphology by its own provides a wealth of data with strong 34 phylogenetic signal and allows inference of major trends in the evolution of this bone.

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“…Isolated quadrates of dromaeosaurid theropods have been well-illustrated for Tsaagan mangas (Norell et al, 2006) and Bambiraptor feinbergi (Burnham, 2004), and a detailed description of the bone is given for Tsaagan mangas (Norell et al, 2006), Dromaeosaurus albertensis (Colbert and Russell, 1969;Currie, 1995), Velociraptor mongoliensis (Sues, 1977;Barsbold and Osmólska, 1999), and Sinornithosaurus millenii (Xu and Wu, 2001).…”

“…mongoliensis (Barsbold and Osmólska, 1999), D. albertensis (Currie, 1995), B. feinbergis (Burnham, 2004) and T. mangas (Norell et al, 2006) is single-headed and articulates exclusively with the squamosal. A 'bistylic quadrate head' (sensu Turner et al, 2007) is present in the basal dromaeosaurid Mahakala omnogovae and may have been articulated with the squamosal and the prootic of the braincase (Turner et al, 2007(Turner et al, , 2011.…”

“…A pneumatic quadrate is absent in T. mangas (Norell et al, 2006), B. feinbergi (Burnham, 2004), V. mongoliensis (Barsbold and Osmólska, 1999) and D. albertensis (Currie, 1995) but present in the basal dromaeosaurid B. gonzalezorum (Makovicky et al, 2005) suggesting that the quadrate may have been pleisiomorphically pneumatic in dromaeosaurids.…”