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Re: FLIGHT VERSUS BROODING
<<But arboreality does not well explain the large sternal plates seen in
small advanced theropods. For two reasons. First, climbers do not have
such large bird-like plates.>>
Juvenile Opisthocomus (hoatzin) individuals have large sternal plates
and a similiar myology to flying birds. No mammals have pectoral
muscles attached to their sternum.
<<Next, arboreal animals tend to have reduced(!) limb muscles (Grand
1977), so they do not need large sterna.>>
Again, no birds other than juvenile Opisthocomus climb, and it has a
typical avian myology. Mammals do not have large muscles attached to
their sternum. I am not sure sure about lepidosaurs, but they (and
mammals) are different from both birds and dinosaurs in that they are
quadrapedal so the forces of gravity are equalized in a different
fashion than bipedal climbers. And according to Bock and Miller, picine
hindlimb and pedal musclature is very strong.
<<Increased attachment area for flight muscles,>>
Or climbing muscles in bipedal animals.
Again, this whole secondarily flightless theropod issue is not supported
by the known phylogeny of theropods and the flight characters can be
explained by arboreality or other processes.
Read Bock and Miller 1959 everybody.
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