Re: Emus a Model for Dinosaurs?

[Michael Skrepnick <palaeopaint@dinosaursinart.com>]

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. . .

http://www.blackwell-synergy.com/links/doi/10.1046/j.1439-0361.2002.02021.x

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*.