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Re: "Flight theory has legs"

--- Scott Hartman wrote:
The best suggestion I've heard to get sinornithosaurs into trees was Greg Paul's
suggestion that the legs splayed, but after looking over high resolution images of the specimens, I cannot confirm that the proximal femoral heads are different from
those of other dromeosaurs. Perhaps better specimens will clear this up, but the bulk of the anatomical evidence for known theropods does not support the needed
degree of scansoriality.

I disagree, there are at least three differences in the femoral heads of Sinornithosaurus milleni and Microraptor gui. Surprisingly, these differences are shared by Bambiraptor feinbergorum and Rahonavis ostromi (and Confuciusornis sanctus and Archaeopteryx lithographica in two cases). I'm wondering if these characters are related to flight, as some are present in volant taxa.

1. Coalesance of the greater trochanter and femoral head (Hwang et al. 2002, Paul 2002)
--- Present in S. milleni, M. zhaoianus, Bambiraptor, Rahonavis, Archaeopteryx lithographica; Absent in Deinonychus, Confuciusornis sanctus.
2. Medio-lateral shortening of the femoral head and neck (Paul, on-list)
--- Present in S. milleni, M. zhaoianus, Rahonavis [?], Confuciusornis sanctus, & Bambiraptor; Absent in A. lithographica, Deinonychus.
3. Very convex dorso-medial region of the femoral head, partially due to the coalesance of the greater trochanter with the femoral head [?] (Look at figs. in Xu et al. 1999 & Hwang et al. 2002)
--- Present in S. milleni, M. zhaoianus, Rahonavis, & Bambiraptor; Absent in A. lithographica, Deinonychus, Confuciusornis sanctus.

Unfortunately, none of these features could be checked in NGMC 91 ("Dave") or the published images of Microraptor gui.

Nick Gardner

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