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Re: Science feather strength debate



Interesting discussion. Early birds may not have flied to avoid
predation or hunt, but only to disperse like seeds. Or, to migrate
from local environments with scarce resources to others more
resourceful. This may not require constant breeze, although it is
certain that there are places with much wind, which are today used in
getting aeolic energy (out of ignorance, I propose that this can in
principle be tested by analyzing how much related to environments
today associated with wind are the environments in which early birds
are found). Being small animals, their dispersive capabilities,
compared with those of larger dinosaurs, were reduced and may require
these tricks, which many angiosperms and arachnids also used.

Now a second thing, cannot the pectoral muscle origin extend farther
than the sternum?
Third, the size of the muscle can be correlated not only with the size
of its origin, but also the size of its insertion, and the humerus is
clearly enlarged in early birds. One can also suggest that some
relative increase in pectoral muscle power would be required, at least
to move the forelimb with similar dexterity as in ancestors with
smaller forelimbs.

Fourth, the lateral surface of the sternal keel does not only give
origin to the downstroke muscles, but also to upstroke muscles as the
M. supracoracoideus. Then, animals with smaller keels may have similar
M. pectoralis masses (pterosaurs? bats?) and thus a similarly powerful
downstroke muscle mass. In fact, according to Ruben (1991) in some
birds, as I suppose in bats and pterosaurs, the upstroke musculature
is not principally represented by the M. supracoracoideus of sternal
origin, but by the M. deltoideus, which originates in the scapula.