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Gregory Paul's dromaeosaur biplanes, dinosaur extinctions: random thoughts



Jim Carey -- whose paper on dinosaur parental care
will, in time, be the basis of an extensive study of
various questions -- has sent me some questions which
I'll outline here for possible discussion.
1. The new Microraptor shows that, ground-dwelling
(predation risk) would have been difficult, and that
tree-living (or in burrows on the sides of cliffs,
e.g.). Unlike most dinosaurs, thus, it "nested" in
trees > incipient parental care.
2. Do the teeth of any of the Microraptors show
patterns and morphologies from which one could infer
nesting building capabilities and/or feeding altricial
young?
3. One wonders if these small dinosaurs were raised
through "fledgling" stages. Do any of the feathered
dinosaur fossil show any indication of a brood patch?
These feathered dinosaurs survived end-Cretaceous
extinction events. The problem of the scenarios, as
Jim writes to me, is that ecological plausibility is
often lacking in discussions of dinosaur extinctions.
Most assume a single event was the causative factor of
dinosaur extinctions (other taxa died, as well).
Theoretical components of a realistic analysis of all
of the available data on the end-Cretaceous
extinctions (note the plural) would fall into four
areas:
1. environmental changes: nuclear winter-types; global
fires; tidal waves; rapid cooling/heating; graducal
reduction of sunlight for months;
2. cause(s) of environmental changes: volcanos,
supernova, "normal" wax-wane in climate;
3. impacts on life histories/ecologies: inability to
adapt, food elimination; outright killing of breeding
populations; growth rate reductions until actual
extinction happens;
4. selectivity: e.g., the arguments on why a)
dinosaurs are pictured (wrongly) as the only group to
experience extinctions, b) why all non-avian dinosaurs
were the only group to experience to complete
extinction, "which is to say," as Jim writes to me,
"why did birds not go extinct but the other dinosaurs
did".
Numbers 3 and 4 are intertwined, and are in need of
serious discussion in vert paleo exegeses of dinosaur
ecomorphologies. As Jim writes: "I think that
understanding the bird survival through K-T boundary
is key to explaining the dino situation; that all dino
extinction theories will be necessary but not
sufficient for explaining the larger questions".
Extinction of most dinosaurs, and the survival of a
clade of theropods amidst this background, are more
complex than some would have it (the end of WALKING
WITH DINOSAURS is an example of an actual event, the
asteroid impact, without further analysis).

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