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Re: [Re: DOWNY STEGOSAURS (WAS: Re: Feathers on Bloody Everything)]



> >>>My question was, if feathers are associated only with birds and birds

> have an

> extremely fast metabolism, isn't it possible that the small carnosaurs had

> a

> different metabolism, and so would not have required feathers?  If so, the

> possible adaptations could be anything from skin (and panting?) to some

> modification of scales.  This is particularly possible if the climate was

> not

> extreme.      <<<

> 

> First of all; the climate WAS extreme.  In the tropics today, animals face

> the same range (= the difference between the highest and lowest

> temperatures) as those in temperate climates.  Remember also, the Mesozoic

> wasn't "warm," it was hot.  Heat is a big problem for endothermic animals

> (try running around naked in Southern Florida in the summer time).  And

> during monsoons, the evaporative cooling can chill an endotherm very

> quickly.  So if you are illustrating endothermic dinosaurs, you need to

> insulate them to be biologically accurate (size counts as insulation,

> above ~400 kg).  Of course, it's hardly been proven that dinosaurs were

> all endotherms.  But with large insulated theropods known (the sitting

> dilophosaurine, and the Chinese therizinosauroid) known, it's starting to

> look pretty good for the endothermic theropods camp.  Also, very good

> papers done on sauropod growth rates placed maturity at around 11 years of

> age (used three different techniques to come to that conclusion), and that

> of hadrosaurs around 6 years.  Your cannot duplicate those rates without

> endothermy in extant animals (and endothermic elephants don't even grow

> that fast, although whales grow faster).  So there's some explaining

> that's going to have to be done by the "dinosaurs are all ectotherms" camp

> if the idea is to continue to be taken seriously. (see my response to

> "haversian systems in lizards" for more on that topic).

> 

> Mind you I'm NOT saying that it's proven that dinosaurs were endotherms,

> or that one has to assume that feathers (or "sinostructures) were on all

> small dinos.  But there are some patterns in the way the evidence is

> heading.  

> 

> Scott hartman

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=================================

So far I have yet to see any convincing 
evidence for deinosaur endothermy.

The sitting dilophosaur was, I believe bad mud
imprints and not feathers.

_Sinosauropteryx prima_ has protofeathers and not 
true feathers.

I'm not sure about _Caudipteryx zoui_

Plus early birds showing signs of ectothermy.

As for growth rates, it has been proven that all
an ectotherm needs is a sufficient supply of food
in order to equal an endotherm.

That's why a green iguana has an average growth in
the wild of 3 years to sexual maturity

Komodo dragons in captivity (and given plenty of 
food) reach 100 lbs in their first year
 
You can get a baby Burmese python and grow it into 
an 11ft animal in 1 year as well.

Oh and estimates for _Architeuthis dux_, the giant squid are basing this
creature as reaching a size of 30ft in only 6 months. 

Ectotherms are quite capable of competing with endotherms in the growth
department.

It just all depends on food access.

At 11 years, sauropods must have been gorged on food.

As for feathers, they seemed to indicate (to me) that they were once
more of a signaling type appendage and not for insulation purposes.

Archosaur J

http://members.tripod.com/~jurassosauridae/index.html

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