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Re: Ornithurine diversity

Tail morphology does affect launch performance, but it is not the primary feature associated with burst launch in animals like pigeons and doves. Some of the more critical burst-launch characteristics include: large pectoralis muscle fraction (esp. pec. minor), improved elevation arc of the forelimb, rapid starting vortex production via wing stroke alterations (clap and fling, AP wing "slicing", etc), altered preload phase with a more vertical push from the hind limbs, and overall reinforced skeletal spar (the proximal forelimbs, especially, are subjected to higher-than-average loads).

In any case, those skeletomuscular features might be a better place to look for evidence of vertical burst launch in Mesozoic birds (not that tail morph analysis isn't important, too). As for the advantages, I agree with John's assessment - it has substantial anti-predation ramifications.



On Saturday, July 12, 2008, at 02:49 PM, john bois wrote:

...even the apparent lack of a proper fanning tail (unknown in enantis this far) might be considered, though I really have no idea how that should help to survive...

If I understand the question properly...a fanning tail is an aid to vertical lift-off. Pigeons (for example) have an amazing capacity for getting high raipdly (hippies take note!). Just quickly, this could aid survival in the following ways: terrestrial (and even aerial) predators have to get closer to affect a catch--this means that a pigeon can react more slowly, eat for a longer period of time, before having to fly off; such birds can also take advantage of food that is in places that have ambush predators...because they can lift off more quickly they can escape predators that would catch fanless birds.
Either or both of these could grant fanned birds more time at feeding sites...so, not only could they feed longer they could live longer.

Michael Habib, M.S. PhD. Candidate Center for Functional Anatomy and Evolution Johns Hopkins School of Medicine 1830 E. Monument Street Baltimore, MD 21205 (443) 280 0181 habib@jhmi.edu