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RE: Saurischia and Ornithischia pelvis
On 2015-07-13 15:28, dale mcinnes wrote:
Ummmm ... could not the forward/ downward projecting pubis
[ancestral position] been selected for in very early and small
for flight to prevent yaw. No known triassic birds yet but, would this
be some indication that more was going on than we know of ? If the
was still reptilian, perhaps, like training wheels on a bike, this
spurred the latter [brain] towards this kind of experiment [flight] ?
evidence. Just thinking out loud here.
Keep in mind: WE have forward pointing pubes. As do parareptiles. As do
lizards (hence the name). It doesn't have to be "for" anything.
If you are looking for the time when selection favored the forward
orientation of the pubis, you need to look in the fish-tetrapod
transition, not in Triassic archosaurs.
The retroversion begins (depending on the exact phylogeny and
optimization of the character) in the ancestors of alvarezsaurs and
pennaraptorans, or at the base of eumaniraptorans. In no case do we have
evidence of an old-fashioned allosaur-style pubis orientation when birds
first showed up.
And I think people are conflating the actual question (orientation) with
the not-related issue of a pubic boot (a distal expansion of the pubis,
regardless of the orientation). The original poster asked about the
position of the pubis.
Thomas R. Holtz, Jr.
Email: firstname.lastname@example.org Phone: 301-405-4084
Geology Office: Geology 4106
Scholars Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Faculty Director, Science & Global Change Program, College Park Scholars
Mailing Address: Thomas R. Holtz, Jr.
Department of Geology
Building 237, Room 1117
University of Maryland
College Park, MD 20742 USA