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Re: How Did Hadrosaurs Survive?
From: John Conway <firstname.lastname@example.org>
Subject: Re: How Did Hadrosaurs Survive?
Date: Tue, 29 Oct 2002 22:54:35 +1100
On Tuesday, October 29, 2002, at 10:26 PM, Tim Donovan wrote:
Newly introducd predators have devastated some ecosystems. The brown
tree snake wiped out nearly all of the native birds on Guam. New species,
including predators, are said to evolve in isolation, then spread.
Essentially there may be little difference between the effects of a newly
evolved predator and a newly introduced one. The advent of Tyrannosaurus
apparently resulted in the extinction of various Edmontonian taxa least
able to fight it or evade it e.g. Euoplocephalus, which was replaced by a
larger Lancian defender.
There is a BIG difference between the effects of a "newly evolved" predator
and a newly introduced one. Evolution of a predator gives time for an
evolutionary response from prey. Predators do not evolve in a vacuum. For
this reason I take exception to the line "advent of Tyrannosaurus", as if
Tyrannosaurus just "arrived". Tyrannosaurus evolved alongside hadrosaurids,
and hadrosaurids with it - show me the fauna with tyrannosaurids but no
As I wrote earlier, Tyrannosaurus probably evolved in far inland
environments given the lack of any close relative in the ornithiscian
dominated lowlands all the way to mid Maastrichtian. Starkov was probably
right: Tyrannosaurus originally appeared in response to Alamosaurus in a
considerably different environment. Its appearance in the lowlands was
probably abrupt, since only about 1 Ma or so separates the upper Edmontonian
from the Lancian epochs. It is possible, even likely, that most
ornithiscians were "taken by surprise" by the spread of Tyrannosaurus to the
lowlands. Indeed diversity waned around this time, when defensive escalation
Euoplocephalus was one of the LEAST able to defend itself?! What possible
reason could there be for thinking so?
Euoplocephalus was adapted to the smaller Albertosaurus and failed to
survive alongside T. rex. The replacement of Euolocephalus with the
consideraby larger Ankylosaurus, which evolved some extra armor lacking in
Euoplocephalus, certainly argues that the latter represented an inadaquate
defense when Tyrannosaurus appeared.
John Conway, Palaeoartist
"Do I contradict myself? Very well, then I contradict myself, I am large, I
contain multitudes." - Walt Whitman
Systematic ramblings: http://homepage.mac.com/john_conway/
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