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Re: Lack of Running Giant Theropod Tracks
On Nov 28, 2010, at 1:49 PM, Don Ohmes wrote:
>> So if there was a drop off in speed (loss of the ability to run) when a
>> carnosaurs/tyrannosaurs reached giant sizes, I'm left wondering why having
>> your prey options limited to the most dangerous herbivores in your ecosystem
>> would have been an advantage.
> Again, I assume you mean sauropods. I am flabbergasted every time this
> comes up on list, and I mean nothing personal in this. Everybody seems
> to agree w/ you, but can offer nothing to defend this intuition become
> an institution.
> Try a thought experiment -- drop down on all fours and become a
> sauropod. Your neck is now as long as your torso, and as big around as
> your finger, or maybe something a little more sensitive. How big is your
> head? Really, really, small...
While a thought experiment such as this may seem intuitive, the reality is that
large vertebrate predators in modern systems rarely attack prey many times
larger than themselves, unless the predator is a powered flyer or a pack hunter
(yes, we can find a long list of one-off anecdotes and the like that show the
occasional exception, but they are rare). Regardless of mobility, potential
vulnerable anatomy, and other factors that we might expect to be major
determinants, the observation is that size matters a great deal. The patterns
are different for some invertebrates (especially r-selected arthropods and
mollusks), but for terrestrial vertebrate predators, even very well-armed taxa
rarely make a meal of animals much larger than themselves hunting solo.
In terms of surprise, I find myself personally surprised at the continued focus
on predation of adults, given that our current knowledge of dinosaur
reproduction strongly implies that there was a vast biomass of juveniles
present for many species.
Assistant Professor of Biology
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