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Re: dino-lice



2011/4/22 Ronald Orenstein <ron.orenstein@rogers.com>:
> In tropical humid forests many species of birds breed over a good part of the
> year, with breeding recorded in every month, so egg-eaters could find nests
> throughout the year.  However, with the exception of African egg-eating 
> snakes I
> cannot think of any vertebrate that eats eggs exclusively; most nest-robbers 
> are
> pretty opportunistic.

Thanks for the insightful answer... Now we may be left wondering that
perhaps the extent of land where Mesozoic amniotes were able to left
eggs all year around may have also been greater than in our days,
given the higher mean temperature, in addition to be greater in
number, because of the larger proportion of egg-laying amniotes
biomass (and thus, likely greater biomass of eggs at a breeding
season). The tropical belt may have been wider than today in a
latitudinal sense, so the offer of eggs may have been greater all year
around in a greater number of places.
Given the general non-homogeneity of several habitats, perhaps the
long limbs of the alvarezsaurs may have provided the possibility to
travel along home ranges relatively large for the size of the animal,
perhaps in order to overcome the fact that some habitats may have
shown greater seasonality than others, and thus a seasonal scarcity
and abundance, even within the tropical belts (If we think about
habitats with greater variance in rains, for example). Alvarezsaurids
may have traveled between patches with a more continuous yearly system
of rains.
Interestingly, I recenly read that anteaters, with similar forelimb
proportions to alvarezsaurs, eat eggs sometimes. But, I suspect they
may not be quite efficient in avoiding the contents oozing to the
ground.

Jason:
Respectfully speaking, your criticism may go to extremes... I mean, an
alvarezsaur arm small enough to be unable to protrude out of the
musculature of the body would support your point, but it seems no to
be the case with the alvarezsaurs known, so it may not be an important
point.
Regarding your display hypothesis, it is tempting to see that the
strong musculature in a small limbs as moving a larger structure,
perhaps as in the endoskeleton of actinopterygian fins. But feathers
are not particularly heavy. And, long processes generally provide
stronger movements, but not fast ones (quite the contrary, faster
extension is provided by a shorter olecranon). So I do not see that
the forelimb skeleton of an alvarezsaur permitted especially fast
display movements.
Although your comparison with a hummingbird humerus is great, we can
doubt of a strict functional similarity in the same grounds by which
you doubt of the trophic hypothesis: the relative size of the
structure is too small in alvarezsaurs to yield a similar function to
that of the hummingbird (as well as the alvarezsaur forelimb likely
lacks the power to break some things an anteater of similar size can,
it also lacks the relative power to make the alvarezsaur perform the
flying style of the hummingbird - I know you do not say this, but then
you have to adapt it to a similar flapping function regardless of
flight - the same we can do while acknoledging the alvarezsaur did not
have the forelimb power -relative to the animal mass- of an anteater).