Re: cause of Gigantism in sauropods

["Habib, Michael" <MHabib@Chatham.edu>]

Excellent points all around.  I actually had the Hone and Rauhut paper in mind 
with some of my comments, and should have cited it in turn; thanks to Augusto 
for doing so (those that have not read the manuscript, I highly recommend doing 
so - I have David Hone's contact info for those searching for a copy).

In any case, the observed clutch sizes and histological data demonstrate an 
r-selection strategy type life history, as you noted, which would necessarily 
imply a large biomass of juveniles unless hatching rates were very poor.  
Assuming that roughly the same proportion of eggs hatched as in modern 
oviparous species, there must have been a huge number of neonates.  While many 
of these undoubtedly died very small, we know that they grew into the 
"mid-range" sizes quickly (histological data), so it seems reasonable to assume 
that a significant number of juveniles at all growth stages were present.

Cheers,

--Mike

On Feb 9, 2011, at 2:52 PM, Augusto Haro wrote:

> 2011/2/9 Habib, Michael <MHabib@chatham.edu>:
>> Personally, I don't understand the insistence that theropods must have been 
>> attacking prey many times their own size, risking death in the process, when 
>> evidence suggests that there was a huge biomass of smaller available prey 
>> (especially juveniles) available for consumption.
> 
> I also believe theropods mostly ate small prey, including juveniles of
> larger herbivorous dinosaurs, following the paper by Hone and Rauhut
> (2010). It may better deal with the perils of getting the head crushed
> as you say, or fall when running after adults, or facing armored and
> probably dangerous prey, as many common larger ornithischians. But, as
> far as I remember, they said predation of juveniles explains the
> scarce preservation of dinosaur juveniles. In such a case... what is
> the evidence supporting the viewpoint there were so many juveniles? I
> think that inferred precocial R-stategies may be some indirect
> evidence, and also sustaining a population of large theropods which
> cannot rely on larger stuff, but arguing this would be circular
> assuming we suppose theropods hunted small juveniles because of their
> abundance).
> 
> Cheers.
> 
> Reference:
> Hone, D. W. E. and Rauhut, O. W. M. (2010), Feeding behaviour and bone
> utilization by theropod dinosaurs. Lethaia, 43: 232–244.

Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
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mhabib@chatham.edu
(443) 280-0181