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Re: AW: Tawa hallae: everything you know about basal saurischians is wrong...




>>>As regards _Tawa_, it lived about 10° north of the Equator, and its 
>>>environment was seasonally almost a desert. The temperatures would have been 
>>>40°C or more even in the shade, of which there was seasonally very little; 
>>>in the sun it must have been worse than Death Valley. Shedding excess heat 
>>>would have been a bigger problem for the incipient endotherm it likely was 
>>>than heat conservation. Vibrissae-like bristles, or a crest of fuzz along 
>>>the spine to convey mood states to conspecifics - fair enough; perhaps even 
>>>more likely than not. Covered in "proto-feathers"? I find that hard to 
>>>believe.

Both lions and ostriches live in desert-like/desert environments that regularly 
have temperatures that regularly exceed 40 degrees Celsius in the dry season, 
and yet both are fairly large animals that are active and homeothermic and are 
covered in furry and feathery integument (respectively). They don't appear to 
have a problem of overheating in these environments with such a covering. Thus 
I don't see why is would be a problem for _Tawa_ to have "proto-feathers". 
Feathers especially can have a two fold purpose: to keep cool air in and hot 
air out or to keep warm air in and cold air out. Whether "proto-feathers" could 
have had a similar function is a subject of speculation. In any case, no one is 
proposing (I would think) a thick coat of "prto-feathers", why not just a light 
coat? Furthermore, that lions have a light coat of fur when they do not "need" 
it for insulation raises questions about the uses of such integument.

Best regards,

Zach


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