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Re: Word from the sole "non-stealthy egg" believer.



On Sun, 17 Nov 1996, Nick Longrich wrote:
>        Raccoon. Monitor Lizard. And the Nile river isn't "swampy".

Varanids may take up to 77% of all nests in a region of the Nile
Crocodile's nests.  But _C. niloticus_ like most crocodiles it lays its
nest close to the water.  That is the point--not whether it is "swampy"
or not, but how close to the water it is.  Alternative hypotheses are
possible (for example a sandy substrate may be the determining factor in
nest site selection), but horizontal and vertical distance from water
would appear to be constrained by the following two considerations: 1.
closeness to the water affords better nest defence, i.e., taking on big
egg predators on their own terms, in their own element--the river. and 2.
Nests must be away from the water to reduce risk of nest loss during
flooding.
        Somewhere between these is where nests are built.
        What is the problem here?  Crocs are comfortable in the water.
They have physical advantage in the water.  If they lay their nests
further in land some of this advantage would without doubt be lost.
Instead of 77% predation it might rise to species threatening levels.
Dinosaurs lay their egg _away_ from the water.  They had no particular
medium where only they were preeminent.  At least _this_ part of my idea
is reasonable.  Now to turn to the host of other reasons (believe me, I'm
glad you could only think of ten!).


>       This "theory" is simply untenable for an incredible number of
> reasons. Here's ten of mine:

> 1) Simultaneity of land extinction events
>       Dinosaurs lived in North America, Europe, Asia, Africa, island
> continents like India, Australia, South America, and Antarctica, and the
> island of New Zealand. Yet they all appear to have gone exinct at once.
> This is an incredible coincidence.

You are depending on negative evidence here.  Just because you haven't
found any dinos after the K/T certainly doesn't mean they aren't there.
Most good dating is from the Northern Hemisphere where continents were
connected.  Even Sereno recently pushed forward the possible continental
connections between Africa and Laurasia to (I think) 100 mya.  I simply
don't trust much of our information on this issue.  We take a data point
and extrapolate the Universe from it.

>
> 2) Simultaneity of sea and land extinctions
>       Ammonites disappear from the fossil record at the same time, and
> about this time calcareaous phytoplankton take a huge hit. How does this
> tie in with the mammals supposed egg predation?

It doesn't.  Temporal distance from these events make us resolve two
events into one.  Also, a blind man shooting at a barn will have clusters
of shots.  These appear connected but are random.  Similarly, historical
events are not uniformally didpersed across time.  They may cluster but
still be without connection.  And anyway, many people disagree with you.
Here is Peter Dodson to shake your ammonite information: "Many
extinctions in the seas (of ammonites, inoceramid and rudistid clams)
demonstrably began at least 6 million years before the final extinction
at the boundary..." (from _The Life and Death 9of Horned Dinosaurs_).

> > 3) Pterosaurs
>       Did pterosaurs choose this particular time to go extinct as a
> result of bird competition? Pterosaurs certainly could have made use of
> the techniques you describe, by nesting in trees, in burrows, or on
> islands, yet the adharchids, apparently enjoying a world-wide
> distribution, went extinct at the same time as dinosaurs.

As you may know, this issue was recently discussed and is far from
resolved.  Indeed, the evidence we have (though it is far from complete)
suggests that pterosaurs were already pretty much done by the K/T.  In
any case, I don't accept this as a compeling argument against my idea.
With regard to competition with birds, they must have been relatively
clumsy and no match for harrying seagull-like forms.

>
> 4) Birds
>       Enantithornes were the dominant birds, yet they went completely
> extinct. In fact, only one small group of the vast diversity of birds
> survived through the extinction event. How would they be any less
> "stealthy" than other birds?
 Yes, this is true.  But an animal can lose the evolutionary stakes at
_any_ part of its life cycle.  "Modern" birds simply out-competed their less
agile cousins.  They were a superior form, perhaps not at the nest, but
in the air.  This advantage was perhaps telling enough to obviate further
explanation.

>
> 5) Ratites
>       Your idea doesn't even allow for the survival, let alone existence
> and diversity, of modern ratite birds.

Diversity?  I assume you mean the large ratites only (because only they
are non-stealthy).  Diversity?  One sp. in Africa.  Zero sp. in Europe and
Asia.  1 sp. in the Americas.  And one only in Australia.  What's that, a
grand total of 3 sp. in the whole world.  Diversity?   Did I miss one?
Surely this is evidence _for_ my idea, not against it.  But the survival
of those species does need explaining.  I will try to do it if
challenged. (Not wanting to take up the necessary space here).

>
> 7) Mosasaurs and plesiosaurs
>       Was the extinction of their friends the dinosaurs just too much to
> bear, so they killed themselves?

Some of these creatures were live bearing weren't they.  This is not
good for my idea.  Then I would hope for some finds after the K/T.  If they
were egg layers they would fall into  the same problems as other large
egg layers--i.e., birds could track them down wherever they layed them.


> 8) Catastrophic extinction
>       The data does not strongly indicate a gradual extinction.

Two things: the subtle tilting of dinosaur growth curve from zero
population growth to slightly negative population growth would have the
effect, from a distance, of a sudden extinction; the rate of extinction
is still strongly contended.

> 9) lack of mammal diversification into dinosaurian niches (i.e. large
> ground animals).

My idea doesn't require mammals to be big.  Just as small things such as
bacteria and virus can affect us, mammals could have done evil parasitic
work on their betters.  Also, birds, lizards, other dinos, and cursorial
crocodiles (by the way, why are their none of these species left?) could
all gio\ve dinos trouble.  The focus of my idea is not mammals, it is the
non-stealthgy nest of the dinosaurs!

> 10) New Zealand
>       If mammals never arrived, dinosaurs should have survived. If
> mammals did arive, then according to your ideas, they should have survived
> much better than non-stealthy creatures like moas.

Much is not known about NZ (as current discussions indicate).  Open
questions remain: When did NZ dinos die out?  Were their any mammals on
NZ at any time (excluding newer bat, rat, cat arrivals)?  What was the
exact trajectory and time of departure of NZ from the mainland?  What was
its fauna at the time?  Why do placentals seem to outcompete marsupials in
some places and not others?  (This is relevant because different animals
are successful in different locations and mammals may not have been able
to cut it at all in NZ.)

Finally, for all anybody knows, BIRDS may have been the
primary agent of dinosaur destruction.  And they did have global
distribution!