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Re: Evidence For a Feathered Velociraptor...

Actually, yes. There's a chapter in, IIRC, Mesozoic Vertebrate Life which investigates the biomechanics of various theropod forelimbs. On the one end of the range the authors find *Tyrannosaurus*, followed by *Allosaurus*: all speed sacrificed for power -- short, massive, columnar bones, small range of motion at each joint, distal muscle attachments (in part accomplished by shortening the bones). On the other they find the birds (an eagle was used), followed by *Deinonychus*: all power sacrificed for speed -- long, gracile bones, large ranges of motion, proximal muscle attachments.

An interesting paper that I will have to look over again. One caveat is that the particular aspects or usage of "power" should be clearly defined. Eagles, in particular, have bones capable of taking very high loads (both bending and torsion) and tremendous mass-specific power. Granted, much of the power from their high muscle mass goes to moving limbs quickly, but there is still plenty of power input.

Of course, you were paraphrasing, and what I figure you mean is that large theropods were found to maximize output force rather than lever arm excursion, and birds were found to favor the opposite (except perhaps in the distal hindlimb of the eagle, which is obviously highly derived within birds). The reason that I am splitting hairs on this is that in the evolution of flight, power to mass ratios are critical. Flying animals tend to generate greater power (and loads) relative to their weight than their non-flying counterparts of similar mass, though the distribution of such power and loads is also quite altered (such that power generation is highly concentrated in muscle groups related to the limbs).


--Mike H.