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Re: Well its not dinosaurian, but nevertheless ..............
This one is dinosaurian, strictly speaking:
Maximal heat dissipation capacity and hyperthermia risk: neglected key factors
in the ecology of endotherms
Journal of Animal Ecology Volume 79, Issue 4, pages 726â746, July 2010
1. The role of energy in ecological processes has hitherto been considered
primarily from the standpoint that energy supply is limited. That is,
traditional resource-based ecological and evolutionary theories and the recent
âmetabolic theory of ecologyâ (MTE) all assume that energetic constraints
operate on the supply side of the energy balance equation.
2. For endothermic animals, we provide evidence suggesting that an upper
boundary on total energy expenditure is imposed by the maximal capacity to
dissipate body heat and therefore avoid the detrimental consequences of
hyperthermia â the heat dissipation limit (HDL) theory. We contend that the HDL
is a major constraint operating on the expenditure side of the energy balance
equation, and that processes that generate heat compete and trade-off within a
total boundary defined by heat dissipation capacity, rather than competing for
limited energy supply.
3. The HDL theory predicts that daily energy expenditure should scale in
relation to body mass (Mb) with an exponent of about 0Â63. This contrasts the
prediction of the MTE of an exponent of 0Â75.
4. We compiled empirical data on field metabolic rate (FMR) measured by the
doubly-labelled water method, and found that they scale to Mb with exponents of
0Â647 in mammals and 0Â658 in birds, not significantly different from the HDL
prediction (P > 0Â05) but lower than predicted by the MTE (P < 0Â001). The same
statistical result was obtained using phylogenetically independent contrasts
analysis. Quantitative predictions of the model matched the empirical data for
both mammals and birds. There was no indication of curvature in the
relationship between Loge FMR and LogeMb.
5. Together, these data provide strong support for the HDL theory and allow us
to reject the MTE, at least when applied to endothermic animals.
6. The HDL theory provides a novel conceptual framework that demands a
reframing of our views of the interplay between energy and the environment in
endothermic animals, and provides many new interpretations of ecological and
With this data, it can probably be estimated how much contour plumage would
have been viable accurately enough at least in some dinos for which it is
disputed. Mb is apparently more susceptible to effects of integumental
structures than to phylogeny. Take a croc as archosaurian baseline, and then
test at which combinations of endothermy and plumage cover extinct dinos of
known size could still dissipate enough heat. This can be correlated with
fossil indicators of endothermy level. I presume that with increasing
endothermy, the maximum viable size for a fully-feathered theropod would
decrease. Of course, external temperatures need to be figured in.