Big Bad Bolide vs. Evil Ecological Encrouching (was KT Boundary)

["Rob Gay" <rob@dinodomain.com>]

> Bolide hypo accepts no burden.  For example, what firepower:angle of
attack:terrestrial substrate:latitude of impact combination would be
required to remove neornithines as well as enantornithines?  What range of
 megatonnage would leave no dino alive, yet leave mammals, birds, crocs to
carry on?<
The energy released/angle of attack/etc. doesn't matter, as long as it's
sufficient enough to stop photosynthesis via orbiting detritus...that's your
primary killer right there. Kill off photosynthesizing plankton=oceanic
ecosystems collapse. Kill off photosynthesizing terrestrial plants go
extinct...and honestly, it doesn't matter if "darkness at noon" lasted for 3
weeks or 12 months, or whatever length of time you prefer...if it lasts long
enough to knock out green plants, its long enough (I don't know enough about
plant biology to say anything about the time certain groups of plants can go
without sunlight)...and what you're left with, in both cases, is carrion
feeders and animals with the ability to control their metabolic rate.
In the above quotation, you say that the bolide hypothesis says that impact
speed and angle of attack are primary to the extinction, and start throwing
out somewhat hypothetical questions. Let me throw some other questions back:
What environmental catastrophe/niche failure/migration could eliminate ALL
seagoing reptiles, many clades of fish, all ammonites, all non-avian
dinosaurs, many avian dinosaurs, many types of mammals, and leave only
moderate sized crocs, some mammals, and some birds, globally?
What wave of outside animals decimated dinosaur populations in India (which
didn't hit Asia until the Eocene, right?)...what environmental change forced
all dinosaurs to go extinct on Madagascar...who invaded Antarctica, forcing
the marine reptiles and dinosaurs to die out there?
While we know that outcompetition does occur, and ecosystems collapses do
occur (especially in this time of man-made dams and pesticides, and what
not), they don't occur on a global scale (man-made ones excluded). While
animal X may force animal Y to extinction in one environment, it does not
stand to reason that Clade X will force Clade Y into extinction...we still
have monotremes around, don't we?!?! Neither marsupials nor placentals have
managed to outcompete them yet...
The global famine/outcompetition scenario just doesn't appear to offer up a
solution to all the questions posed by the MASS extinction...you're wary
because the impact theory does. It's good to question, of course (which is
why I'm really enjoying this conversation)...but if one hypothesis better
fits the evidence than another, there's probably a reason...
Peace,
Rob

Student of Geology
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