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Re: taxonomy is not stratigraphy (was Re: JVP 25(2): New Dinos, Birds, Discoveri
Denver Fowler (email@example.com) 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
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.>
Unfortunately, the nature of science and inferrence requires us to find
analogues to test to form theories of ecosystems we cannot observe for 20 years
on the veldt. While the argument is just, it is only just SO. There must be a
means to test the assemblage of fossils in a way that utilizes the data,
however fragile and incomplete it is, otherwise we are left with data
collection and nothing more. The only large ecosystems we have available
involving macro predators, micro predators, and multiple large and small
"herbivores" (prey and omnivores) by which to test a similar apparent faunal
assemblage (albeit each element being by degrees larger) are few and far
between. They are usually marine, and the most large terrestrial systems we
have are in Africa. Part of this reason may be due to major human transgression
into North America, unbalanced hunting regimes as most newly introduced groups
seem to favor, but not balance progressed. In Africa, man developed with the
fauna, unlike in the Americas, and thus it seems the African ecosystems
represent a more stable fauna by which to examine similarities and differences.
Inferrence of how approproate this is can be made when data is presented. Does
this invalidate the use of the system chosen as an "analogue"? No.
In addition, the African savannah is only one such system in which the
African principles are known. Cape hunting dogs prefer the veldt to the south,
whereas ostrich and ibex prefer the more arid north. Jungles along the equator
tend not to carry very many large herbivores, much less megaherbivores. But
veldt and savannah represent the best regions in which to observe accumulation,
interaction, conflict, and predation, as well as through direct sampling,
changes in the "arms" and "size" races that seem to be more "just so"
interpretations of similar data.
It is for these reasons I think the use of the more diverse African faunas
are valuable information tools.
<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.>
The seasonalities of the tropics are, by definition, virtually non-existent.
They are tending to "wet" and "dry" rather than "hot" and "cold". Or more
essentially, "hot" and "hotter".
Seasonality is often used to mark change in weather (which is recorded in
Mesozoic sediments as having both hot and cool trends and therefore at least
mild seasonality [as in the tropics]), as well as in reference to migratory
patterns (which also appeared to have existed with inferrences of herding
behavior and patterns of herd structure, which cannot be maintained in small
areas, as well as _seasonal_ nesting sites for hadrosaurs and sauropods). So I
am not sure that seasonality is a neccessary deterrent to inference.
<Lions only exist in prides because of the need to hold down a large territory
because of migrational prey.>
This strikes me as a just so story. How is this different than, say,
alberotsaurs tracking hadrosaur or ceratopsian herds?
<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.>
A point which I was hoping I had gotten across with the last post. But this
is using the savannah as the analogue to the Mesozoic. Modern for past. It is,
after all, the only way to test the fossil data. Ask a question: What is the
structure of the Morrison ecosystem? One will tend to look to a modern
ecosystem to test any resultant "just so story".
<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.>
I think Greg Paul tried to do this by showing allosaur family life, and an
allosaur laying about, scratching itself. I do not think that intelligent
people will think that animals spend 100% of their time running around, making
loud noises and drooling for human meat. Just an idea ;).
Jaime A. Headden
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
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