[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
2011/4/22 Ronald Orenstein <email@example.com>:
> A snail-picking adaptation might have led to a digit such as those in
> alvarezsaurs, but why would the other digits be lost (they might be useful in
> picking the animal out of the shell, for example)?
May be, but I was thinking perhaps just a hook is optimal for
snail-hooking, and that a similar development of other fingers may
> And why would such a
> strongly-muscled arm be required?
I think the forearm is strong relative to the size of the forearm, not
so much relative to the size of the entire animal. Perhaps no more
than in coelurosaurs with longer limbs. Before I wrote (but think it
did not reach the list), that, so to speak, you choose the size of the
pincer according to what do you want to pick. You would not use a
pincer used to remove nails to extract a barely visible splint from
your skin. So, perhaps if you want to break large termitaria, you use
a large, strong forelimb, as in anteaters, pangolins, giant armadillo,
etc. If you need to break something small, you may more economically
use a smaller version of this. If you need to partially break a small
thing (I was favouring perforating eggs for the thin snout to enter
the hole, and to avoid its contents oozing), you need greater
precision and this is given by a small version ot the same principle.
For example, a large knife may be useful to get slices of a large
vegetable, but may crush a small vegetable, where slices may be better
made with a small knife.
By the way, a question to you, which are an ornithologist: Do all
birds deposit their eggs in the same season of the year in a given
place? Because if this is true, then egg-eating (my favourite
hypothesis) would not be so easy the rest of the year...
> If the arms were used in foraging it seems more likely that they would have
> been used as levers against considerable force
> -- perhaps pulling apart some tangled mass of plant fibres or ripping into a
> cycad trunk, for instance -- if they had access to some sort of trunked or
> otherwise erect plant the difficulty of them having to stoop to ground level
> burrow might not exist. Could the arms of alvarezsaurs be analogous to the
> enlarged rooting teeth or tusks of some herbivorous mammals - given that tooth
> modification was not on the cards for them - rather than to any limb structure
> in another animal?
These are possibilities... Indeed, they may not be mutually exclusive,
because many structures can give many good uses, and perhaps looking
for the one which was selected for implies dismissing the possibility
that having something good for many uses, instead of specialized for
the best performance at a unique task, in itself was something to be