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

[Dann Pigdon <dannj@alphalink.com.au>]

On Fri, Feb 25th, 2011 at 10:37 AM, Tim Williams <tijawi@gmail.com> wrote:

> The isotope ratios of certain spinosaur remains are about the
> same as contemporary crocs (Amiot et al., 2010) ... so if spinosaurs
> spent less time immersed than crocs, does that mean that these
> spinosaurs had a higher proportion of aquatic prey in their diet than
> crocs (in order for the oxygen to shift isotopically to the same
> degree)?

You would need reliable data on the proprotion of time that crocodilians spend 
basking verses 
immersed in water before you started asking such a question. Crocs need to bask 
out of the water 
in order to raise their body temperatures, so the relative time proportions of 
basking verses 
immersion will be different at different latitudes and altitudes. Very hot 
climates will result in more 
time spent in the water to cool down, while cooler climates would result in a 
lot more basking. 

That all assumes that Cretaceous crocs had similar physiology to modern crocs. 
I suspect that 
the 'running crocs' may have retained a more endothermic metabolism - although 
they may not 
have spent much time in the water at all.

A croc that spends 50% of its time basking (to pluck a figure out of nowhere) 
might have a 
similar 'immersion factor' to a spinosaur - except that the spinosaur is going 
about it's cursorial 
business when not wading or swimming, rather than basking.

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