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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.
As for the diet, curlews, godwits, and sandpipers do fine in the arid zone
floodplains of inland Australia with gracile, edentulous, beaks.
> 2011/4/20 Augusto Haro <email@example.com>:
>> If we
>> talk about breaking bark, we do not need to hypothesize unique
>> reliance on social insects, for arthropods in general on rotting trees
>> may be made available.
> Now I read Thomas Holtz's assertion that alvarezsaurs lived in mainly
> treeless habitats, and Tim's assertion that cursorial animals do not
> show low metabolic rates, while ant-eaters above 1 kg. do. My opinion
> is that alvarezsaurs may have been omnivores eating soft foods that
> needed not to be cutted or teared with its delicate snout, as insects,
> small animals in general and soft plants or grains. But, for accessing
> to them, may we envisage some other thing which is hard but can be
> breaked up by putting point pressure upon it? Perhaps large
> seeds/fruits, hardened soil (if the alvarezsaur had a rather good
> smell), relatively large eggs of other dinosaurs? I do not know.
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