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Re: taxonomy is not stratigraphy (was Re: JVP 25(2): New Dinos, Birds, Discoveri



>>> Simply put, if you take the adult size of any of
the
potential prey species of a large dinosaur predator,
then think that this animal produced as many as 10-30
young per year, taking on average much longer to
mature than equivalent mammals (especially given the
fact that they were an order of magnitude larger as
adults, and significantly smaller as juves), then
there is no shortage of potential non-adult prey for
given predators. Although it is undoubtedly sexy,
dangerous, and exciting to think of large theropods
attacking adult herbivorous dinosaurs, really there is
no requirement for them to do so. The sheer number of
non-adult individuals of these prey species would
provide an almost limitless bounty.<<<

Were the large theropods existing in a vacuum? No
medium or small predators? Surely it is a safe
assumption that the competition for sauropod flesh was
intense at all stages of development. Note that as
sauropods progressed to adulthood they would outgrow
their predators in a size sequential progression,
providing an (at least seasonal) positive size
selection for the entire predator suite. Perhaps the
adult sauros were out of reach, but that doesn't
negate the advantage of predator size. In fact,
logically it augments the selective advantage of
predator size by reducing available resources and
increasing interspecific competition. "Almost
limitless bounty"? In theropod dreams, maybe. 

--- Denver Fowler <df9465@yahoo.co.uk> wrote:

> When it comes to comparisons, far too many people
> look
> to the african serengeti for parallels with dinosaur
> evolution and ecology. These comparisons are
> understandable: the african savannahs are very
> easily
> observable: big open plains with some very large
> inhabitants, and they do contain an ecosystem
> largely
> unaffected by the megafaunal extinctions of 10ka
> (hence reasonably intact).
> 
> However, much of what people believe they understand
> about these places is subject to much bias, and alot
> of that is subject to what a handful of TV producers
> thinks looks good, or is biased by the fact that the
> savannah is an unusual megafaunal ecosystem.. even
> for
> africa.
> 
> Really, savannah ecology is an inappropriate
> comparison to that of dinosaurs. First of all,
> savannah relies upon seasonal grasslands, which is
> of
> course an entirely non-mesozoic phenomenon. Lions
> only
> exist in prides because of the need to hold down a
> large territory because of migrational prey. Much
> <admittedly not entirely solid> evidence points
> towards north african lions living a mostly solitary
> existence (before they all disappeared, and in
> concordance with pretty much all other known felid
> species), and indeed <of course> most male savannah
> lions live such an existence. We don't see these
> guys
> on TV so much, because they aren't nearly as
> exciting
> as seeing pride hunting females, nor as
> politico-socially interesting as seeing a bunch of
> lionesses do all the work for a big old lazy male
> (or
> pair of males). But male lions constitute 50% of the
> actual lion population, even if they barely make it
> onto TV at all (males that take over prides might
> end
> up lazy, but all the other poor buggers have to go
> hunt their own lunch, and frequently hunt smaller
> prey, thereby creating a separate niche from the
> female pride-lions).
> 
> Then there is the point that typical large mammalian
> herbivores produce at most 2 young per year,
> typically
> maturing relatively quickly. thus biomass (regarding
> potential prey for mega-predators) in most modern
> mammalian ecosystems is tied up in at least
> subadult-size animals. dinosaur demographics were
> entirely different to this, and likely had no modern
> analogue.
> 
> Simply put, if you take the adult size of any of the
> potential prey species of a large dinosaur predator,
> then think that this animal produced as many as
> 10-30
> young per year, taking on average much longer to
> mature than equivalent mammals (especially given the
> fact that they were an order of magnitude larger as
> adults, and significantly smaller as juves), then
> there is no shortage of potential non-adult prey for
> given predators. Although it is undoubtedly sexy,
> dangerous, and exciting to think of large theropods
> attacking adult herbivorous dinosaurs, really there
> is
> no requirement for them to do so. The sheer number
> of
> non-adult individuals of these prey species would
> provide an almost limitless bounty. 
> 
> The tendency of televison producers, and scientific
> researchers, to dwell on savannah ecology the last
> 20
> years or so (understandable, since it is so easily
> filmable and exciting, and given socio-economic
> advances), has led to bias in how people want to
> interpret dinosaur ecology. The simple fact is that
> most modern predators hunt alone. Most modern
> predators hunt prey signficantly smaller than
> themselves. If you want to use modern ecosystems as
> a
> comparison then you should draw the conclusion that
> tyrannosaurs et al lived lives not nearly as
> exciting
> as Hollywood might like us to believe.
> 
> Denver.
> 
> 
> biomass in dinosaurs is 
> 
> 
> 
> --- Ivan Kwan <dino_rampage@hotmail.com> wrote:
> 
> > >While the argument of massive herbivores being
> the
> > selective pressure for
> > >massive carnivores is a wonderful story, it
> doesn't
> > seem to play out in, at
> > >least, any modern ecosystem. All super carnivores
> > today are many times 
> > >smaller
> > >than half that of the largest herbivore in the
> same
> > ecosystem.
> > plus the fact that hunting buffalo must be
> > infinitely more rewarding than 
> > scuffling over warthog piglets during the dry
> > season. (Think this must be 
> > some prerequisite for almost any documentary
> > featuring lions - insert long 
> > drawn-out battle between buffalo and lions)
> > 
> > In any case, the idea that theropods evolved
> > gigantism in response to the 
> > ever-increasing size of sauropods is a tantalising
> > idea, but unfortunately 
> > one that I'm afraid is difficult to test, due to
> the
> > imperfection of the 
> > fossil record. However, at the moment, at least, I
> > think we do have evidence 
> > that it was the herbivores that first 'developed'
> > the tendency to grow to 
> > much larger sizes, case in point being the
> > prosauropods/basal 
> > sauropodomorphs. Unless there are actually some
> > 20-foot long 
> > coelophysians/herrerasaurs/avepods that I've
> > forgotten about.
> > 
> > Ivan
> > 
> >
>
_________________________________________________________________
> > Take a break! Find destinations on MSN Travel.
> > http://www.msn.com.sg/travel/
> > 
> > 
> 
> 
> 
>       
>       
>               
>
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