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Re: Emus a Model for Dinosaurs?

Appears that applies for sauropodomorphs and is similar to ornithischians, first illustrated in Galton ( the brevis portion of m. caudifemoralis running from the posterior ilium to the 4th trochanter and onto a tendon inserting into the gastroc. and proximal tibia, while pars longus originates on the proximal caudal series ).

In answer to the original question I found a summary online from Christiansen / Bond here. . .


of particular interest is their assertion that center of gravity remains the same in Caudipteryx as in all other non-avian theropods and if so negates the necessity of a shift in hindlimb locomotion from the hip to the knee. . . and as such, lack of a 4th trochanter does not imply a dorsal shift of the insertion, ( or the loss ) of any part of the caudifemoralis into a neornithine condition. If the reduction in caudals was not enough to affect hindlimb movement in Caudipteryx itself, I wonder if there is any impact in oviraptorosaurs like Nomingia having further reduced caudal series / pygostyles. . . are any secondarily flightless theropods ( or those initially evolving flight ) subject to a shift in hindlimb locomotion, or is this strictly relegated to neornithes / advanced birds?

. . . am still interested in why a 4th trochanter would evolve in Velociraptor and not Deinonychus, when except for size, both have nearly identical design which would seem to dictate similar patterns of movement. Why would animals evolve an extension of bone for muscle insertion / attachment that is functionally not necessary? Obviously excesses of ornamentation develop in dinosauria for species recognition, etc. . . but I have been under the impression that in terms of post cranial anatomy, a vertebrate skeleton only need adapt minimally to the stresses put on it by body size and outside environmental concerns ie. the range of topography in which it lives and modification as either predator or prey, in order to stay one step ahead of the other.

Mike S.

Not that I knew any myology... the description of the pelvis and hindlimbs of *Saturnalia* says the caudifemoralis did not insert on the 4th trochanter but medial to it, while the trochanter itself was the attachment point for something else, IIRC the gastrocnemius. Of course this would still not explain the difference between *Deinonychus* and *Velociraptor*.