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K/T impact (was Re: [for some reason] Tim's theory)
Of course, the prediction of their survival is confirmed. In
contrast, the asteroid theory rather poorly predicts what is observed.
Frankel mentioned oven-like temperatures followed by darkness and cold.
"Oven-like temperatures" - surely not world-wide.
former should have wiped out life far more indiscriminately.
Among marine invertebrates and "protists", ammonites and forams also went
extinct at the K/T boundary. Apart from dinosaurs, many other groups went
extinct, both macro- and micro-sized, marine and terrestrial: pterosaurs,
sea reptiles, toothed birds, ammonites, rudists, forams, coccolithophorids
have been just as vulnerable as dinosaurs.
Only a trickle of avian diversity (and disparity) survivied the K/T
boundary, in the form of the neornithines.
Arboreal mammals, etc. should
have gone up in smoke with the trees.
Certain mammals were hit hard (at least the marsupials). As for them "going
up in smoke", see below.
Severe cold and darkness should have
devastated the reptiles, especially crocodiles, but the latter survived
at fairly high latitude.
I think you may be conflating the short-term effects the actual impact had
on animal life (a few seconds) with the more long-term effects the impact
had on the world ecology (thousands of years). Sure, any living thing close
to Ground Zero would vaporize. But what killed off the dinosaurs (and all
the rest) was probably a slow, creeping deterioration of ecosystems as
plants (and phytoplankton) could no longer photosynthesize as effectively
under such dim conditions.
The extinctions percolated from the bottom of the food chains upward. The
devastating effect that prolonged darkness and cold conditions (perhaps
followed by elevated Greenhouse-like temperatures, as the ash and dust
settled but the CO2 stayed up in the atmosphere) would have on life
everywhere cannot be overstated.
I can't tell you why crocodilians and turtles survived the Cretaceous and
plesiosaurs and sauropods didn't. Nor why enantiornithines went extinct and
neornithines survived. Maybe the survivors possessed certain adaptations
which those that went extinct lacked. Maybe it was just dumb luck.
All things considered, the asteroid theory is greatly overrated and
there should be greater receptiveness to alternative hypotheses.
And the iridium spike?
P.S. Who is the "Tim" in "Tim's Theory"?
Timothy J. Williams
Iowa State University
Ames IA 50014
Phone: 515 294 9233
Fax: 515 294 3163
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