dinosaur thermoregulation

["James Farlow" <farlow@ipfw.edu>]

I very much doubt that we can ever provide a detailed answer as there may have 
been physiological or behavioural mechanisms that left no fossil trace. I 
expect panting and gular fluttering were present, but a host of other 
mechanisms 
including bathing, resort to shady areas, or highly-vascularized skin patches 
(I 
presume that the sails of spinosaurs or the3 plates of stegosaurs are probable 
examples). 


Farlow: If I might jump in here, some colleagues and I recently published a 
paper in _Swiss Journal of Geosciences_ that considers some aspects of 
dinosaurian thermoregulation, with lots of references from the literature (and 
there's a lot of this, once you start digging into it) about modes of 
physiological thermoregulation in extant amniotes. Given the diversity of body 
sizes and forms, differences in integument (feathers vs. scales), and 
differences in the climates to which they were exposed, among non-avian 
dinosaurs, I would guess that which modes of heat exchange were most imortant 
varied across taxa. But judging from what we seen in modern amniotes, I would 
expect that evaporative cooling would have been very important, especially in 
forms with big mouths (imagine a tyrannosaur crouched on the ground something 
like an emu, dozing, with its head on the ground and its jaws agape). Control 
of blood flow from the body core to the periphery would probably have been 
important in most or all forms, and I would expect blood flow to parts of the 
body with higher surface/volume ratios (often generalized under the label 
"appendages" in the physiological literature) than the body core to have been 
significant; appendages in this sense can include limbs, of course, but also 
tails and necks (sauropods, maybe?), and maybe any funky vascularized thingies 
sticking out away from the body (the last of these being a personal favorite of 
mine). 

And never forget behavioral thermoregulation, which acts in tandem with 
physiological mechanisms, reducing the metabolic cost of the latter. Standing 
under shade on a hot day, or soaking in a body of water, or--in really hot 
climates--being most active at night can do wonders for keeping your cool.