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




--- don ohmes <d_ohmes@yahoo.com> wrote:

> Perhaps I misinterpret a couple of recent posts,
> but--
> 
> I was taught that the largest herbivore is always
> larger than the largest predator. 


 Not necessarily true in the Hell Creek.


>The quantitative
> size differential may be affected by various
> strategies (e.g., in predators; pack vs solitary
> hunting, and in prey; defensive herding behavior,
> armor), but the general trend is intact through
> time.
> I am also under the impression that when graphed
> such
> that the y axis = kg, and the x axis = geologic
> time,
> there is a strong positive correlation between
> largest
> herbivore and largest predator.
> 
> Surely the fact that the herbivores sometimes (or
> even
> usually) "win" doesn't falsify the hypothesis that
> there is a mutual selection for size operating
> within
> the "top" predator/prey relationship? After all, if
> the prey doesn't "win" the size race, swift
> extinction
> is a likely result for both, in which case they
> might
> not appear in your data base.
> 
> Sauropods may have "won",


  Only in the sense that they were big and powerful
enough to survive. Sampson concluded that T. rex was
present in the North Horn with "Alamosaurus" and
therefore the unit is probably Lancian equivalent, and
the predator persisted there to the end. I think
Tyrannosaurus evolved large size to be able to prey on
titanosaurs as well as other prey in far inland
environments. Tyrannosaurus spread to the lowlands,
lacking titanosaurs, because it was a generalist and
its large size enabled it to outcompete Albertosaurus.
Lowland prey became more escalated-though not all prey
survived-resulting in equilibrium.




> and packhunting
> tyrannosaurs
> may have turned to smaller prey. After morphing into
> solitary hunter/scavengers, intra-specific
> competition
> for food and the implications of a solitary hunting
> technique might have dealt the final cards relative
> to
> the size of tyrannosaurs. This doesn't de-couple the
> more general evolutionary relationship between
> sauropods/therapods relative to size. Details may
> never be available, but isn't safe to assume that
> sauropods were subject to predation at all times,
> and
> were affected in the evolutionary sense?
> 
> --- "Jaime A. Headden" <qilongia@yahoo.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.
> > 
> > Wolf vs. Carribou/Elk
> > Bobcat vs. Moose?
> > Lion/Tiger vs. Elephant/Water buffalo
> > Orca vs. well ... any mysticete
> > 
> >   etc.
> > 
> >   None of these "superpredators" are capable of
> > taking on the "prey" without
> > inconventience of the latter or assistance of
> > numbers of the former. To
> > determine in the past whether such behaviors
> occured
> > requires extraordinary
> > evidence. 
> > 
> >   In the Serengeti, lions will not take on a water
> > buffalo unless its disabled,
> > stuck in mud, or sick. Smaller (read: weaker) and
> > seldom full size and
> > full-health animals fall to either lion or wolf,
> > because even in numbers, the
> > mass of the animal is prohibitive and not
> conducive
> > to continuing-health.
> > 
> >   We have, at Cleveland-Lloyd Dinosaur Quarry, a
> > "predator trap" with a massive
> > concentration of carnivores but with -- by numbers
> > -- much fewer herbivores.
> > This seems exemplative of such weakened, disabled
> > animals as to be picked on by
> > groups or phases of predators.
> > 
> >   To be big, perhaps, as Nick said, is to prevent
> > predators from killing you.
> > Herding permits animals to grow bigger with less
> > reduction of the population.
> > So it seems Mesozoic dinosaur herbivores were
> either
> > tiny, armored, huge, or
> > bore offensive anatomy. This seems a response that
> > was rather effective. Of
> > course, just so stories can explain either
> herbivore
> > preventive size-gain, or
> > theropod offensive size-gain, but in the end ...
> the
> > only way to determine an
> > animal killed another is with something like the
> > Fighting Dinosaurs (and even
> > _that_ is ambiguous).
> > 
> >   Cheers,
> > 
> > Jaime A. Headden
> > 
> > "Innocent, unbiased observation is a myth." ---
> P.B.
> > Medawar (1969)
> > 
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> 
> 
> 


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