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RE: How Did Hadrosaurs Survive?



David Marjanovic (david.marjanovic@gmx.at) wrote:

<And of course I forgot the third aspect, the Limited Catastrophe model
aka Survival of the Imperfect:>

  Sounds like adapted perfectly for the scenario, to my mind. Nature finds
balance, simple and easy, when things develop as they do and are not
manipulated.

<Anteaters dig termite nests open. They eat for 5 to 10 minutes, stop,
clean their fur painstakingly and go on to the next nest. Results in a
dozen nests and 5 to 10 km per night. What for? Why don't they open fewer
nests and eat them empty? In hindsight it's clear: it's resource
management, the anteaters keep the nests alive. But how do they know? It
turns out that about 5 min after a nest has been opened the termite
soldiers have reached the anteater's skin and bite so the anteater has to
stop. Anteater skin is not optimally adapted. How come? It can't be a
design constraint, vertebrate skin is enormously adaptable, close
relatives of anteaters like armadillos and, to a lesser extent, ground
sloths have evolved armor.>

  Actually, armored skin is the plesiomorphic condition. Primtive
vermiliguans, tardigrades, and cingulatans have about as effective a coat
of armor as little studs of bone in the skin all over. Anteaters lost
theirs, armadillos and glyptodonts improved theirs, sloths reduced theirs.

<The idea here is that if a mutation occurs that increases fitness beyond 
what is sustainable in the long term, it spreads throughout the deme, and
the deme dies out before more can happen. [...] So any armored anteaters
have starved long ago.>

  Er, no. This is not a logical conclusion to the theory. Armor just
insn't good for a group of animals that are not terrestrial, and nearly
all vermilinguans have been at least somewhat arboreal. *Myrmecophaga* is
nomadic, and loss-of-armor can be considered a weight-saving device, but
primitive myrmecophagids are not plentiful in the record either, obscuring
the exact reason anteaters lost armor. Though it is true increase of
performance would decrease the food stock, it is perhaps more of an
"intelligent design" scenario to suspect that these animals are regulating
populations, in case they die. An animal when hungry does not stop trying
to feed because it might eat too many food items.... The original idea,
that this is how long it takes for the soldiers to come to the defense, is
more reasonable, since it involves an ecological defense of the prey to
being destroyed. This is also in effect the oft-noticed formicine response
to destruction of their nest. The immediate termites let off a chemical
signal that says "danger", and its off to the rescue. You also see the
same behavior in Africa in response to aardvarks, which have thicker skin
and do not readily scout for a few tasty morsels per mound.

<And the simple observation that *Tyrannosaurus* survived for millions of
years looks like good evidence that  it wasn't an Ultraraptor (search the
archives of 1999 for this term if you need it).>

  Its regulating the stock cowboy style?

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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