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The extreme musculature indicated by the ossified keeled sternum and big
olecranon process combined with an enormous claw leave little doubt that
alvarezsaur arms where for tearing something apart. The shortness of the arms
increased their power via leverage. I like to think it was termite mounds,
which I believe have been discovered from that time. Display feather fluttering
does not explain any of the features.
In a message dated 4/20/11 2:46:08 PM, firstname.lastname@example.org writes:
<< The problem with imagining Mononykus tearing open conifer cones with its
arms is the same as picturing it digging into insect mounds. It couldn't
reach the ground from a standing position. Its arms, fully extended,
could not even reach the knee.
Present company considered I'll engage in a little a priori speculation
and say that it seems unlikely that there would have been selection
pressure toward shorter, reduced, arms in your scenarios. If shorter arms
went along with clawing behaviors then we are imagining an animal that
would have to squat down on top of an anthill and then dig under its
belly, as a storm of angry hands poured out over its body. The arms could
have maintained their ancestral, long, state and functioned just fine in
opening insect colonies, bark, or pinecones.
According to Senter(2005) Mononykus also could not hold anything between
Selection pressure could have driven shorter arms with larger muscular
processes if there was selection for high frequency fluttering of a fan of
feathers or ribbons.