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

[Ivan Kwan <dino_rampage@hotmail.com>]

----Original Message Follows----
From: "Jaime A. Headden" <qilongia@yahoo.com>
Reply-To: qilongia@yahoo.com
To: dinosaur@usc.edu
Subject: Re: taxonomy is not stratigraphy (was Re: JVP 25(2): New Dinos, 
Birds, Discoveries)
Date: Fri, 15 Jul 2005 22:45:04 -0700 (PDT)

> 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

If you're talking about the Arctic tundra, that is. Elk are restricted 
largely to forests and woodlands, it seems. Otherwise the largest herbivore 
the grey wolf interacts with would be the American bison. In Eurasia it'd be 
the European bison, or the Megaloceros, aurochs, woolly rhinoceros, woolly 
mammoth and steppe bison in the good ol' days of the Pleistocene (plus all 
the miscellaneous Stephanorhinus and Palaeoloxodon/Elephas species hanging 
around during the interglacials).

And besides, it's important to take note that the wolf may be considered a 
'top' predator now, but what about in the Late Pleistocene? I wouldn't be 
surprised if in North America, the grey wolf and puma were much lower and 
had to defer to the dire wolf, American lion, sabertooth, scimitar cat and 
short-faced bear...

And in Eurasia, the wolf probably would be competing with cave lion and 
spotted/cave hyena, as well as the tiger in the Asiatic parts of its range.

> Bobcat vs. Moose?
> Lion/Tiger vs. Elephant/Water buffalo
> Orca vs. well ... any mysticete

You could throw in brown bear/grizzly as the largest carnivore for the 
Eurasian and North American ecosystems, but I don't think it really counts 
as a "super-predator"

As for the big cats, lions would be taking on African elephant, cape buffalo 
(water buffalo are exclusively Asian), white rhinoceros, black rhinoceros 
and common hippopotamus, while the largest tigers (if we're talking about 
Indian tigers) would be facing off against Asian elephant, Indian 
rhinoceros, (plus Sumatran and Javan rhinoceros which once ranged into 
eastern India as well), and water buffalo. Siberian tigers would be up 
against moose, steppe bison, woolly rhinoceros and woolly mammoth (provided 
these were sympatric with Siberian tigers in the Pleistocene).

> 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.

Not too sure if we have any real data on that, since there do seem to be 
lion prides that specialise in killing Cape buffalo, even adult cows and 
bulls. Desperation and hunger may play an important role in that as well, 
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

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