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Re: The Very Very Latest Paper From 2006!!!



I think you missed my point, not that my point is necessarily valid. 

Restating-- Large animals have low surface mass ratios, and therefore lose heat 
more slowly on a mass specific basis than smaller animals. It follows that 
direct ambient temperature effects on growth are more pronounced in small 
animals more than large, and LAGs would therefore be less defined in larger 
animals, and would disappear entirely at some size. 

Assuming elephants are really 'LAG-free'-- If the body size at which LAGs 
disappear entirely is significantly larger in dinos than mammals, then that 
supports the idea that dino growth (and by implication, body temp) at a given 
body size was more strongly affected by ambient temperature than mammalian 
growth is, (or was). Due to the obvious seasonal effects on food intake of 
herbivorous animals, well-defined LAGs in the largest carnivorous dinos add 
another layer of support to this thesis, as they are larger than the largest 
herbivorous mammals, yet in theory not as subject to seasonal nutritional 
limitations... 

Also-- To change the subject slightly, would endotherms show a proximal/distal 
limb bone LAG definition gradient?

Don

----- Original Message ----
From: David Marjanovic <david.marjanovic@gmx.at>
To: DML <dinosaur@usc.edu>
Sent: Thursday, March 8, 2007 5:29:19 PM
Subject: Re: The Very Very Latest Paper From 2006!!!

----- Original Message -----
From: "don ohmes" <d_ohmes@yahoo.com>
Sent: Wednesday, March 07, 2007 9:34 PM

> Elk are probably relatively far up the surface/mass ratio chart from 
> elephants though. I'm just saying that if the LAGs disappear in both the 
> largest dinos and the largest mammals, AND there are commonly dinos w/ 
> well-defined LAGs that have significantly smaller surface/mass ratios than 
> the largest (temperate or cold climate) mammals, then that is relevant to 
> the debate about their respective thermo-regulatory systems.

But why, when horses and rhinos and cattle also have LAGs -- and don't show 
differences between proximal and distal limb bones?

I guess the largest mammals and dinosaurs have to grow faster and can't 
afford, erm, lags in their growth.