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Re: What did Spinosaurus eat? New species of Lepidotes found



On Tue, Feb 22nd, 2011 at 1:43 PM, quailspg@frii.com wrote:

> Tim Williams wrote:
> 
> > Is there something about birds that allowed them
> > to exploit aquatic niches in the Mesozoic?
> 
> Development of water-resistant and/or air-trapping plumage?

For a diving bird, air-trapping plumage can be a distinct disadvantage. Some 
diving birds, such as 
cormorants, lack water-repelling oil on their feathers - specifically to allow 
the feathers to become 
water-logged to make the animal as heavy as possible while diving. The avian 
body plan is already 
extremely bouyant, even without trapped air beneath the feathers.

I imagine that non-avian theropods would have had similar problems where diving 
was concerned, 
with their avian-style respiratory systems. Perhaps large theropods were 
prevented from becoming 
habitual divers because of their inherant bouyancy.

Having giant crocs, pliosaurs and mosasaurs in the oceans and waterways 
probably didn't help 
much either. Large theropods would have had a hard time competing with them in 
deep water - 
especially if they were stuck bobbing like corks at the surface and making 
appetising targets of 
themselves. However spinosaurs probably had the 'mega-wader' niche largely to 
themselves.

-- 
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Dann Pigdon
Spatial Data Analyst               Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
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