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Re: Word from the sole "non-stealthy egg" believer.
On Sun, 17 Nov 1996, John Bois wrote:
> On Thu, 14 Nov 1996, Mickey P. Rowe wrote:
> John Bois wrote:
> Crocodiles were niche sovereigns. They remain so today. Would-be egg
> thieves are loathe to enter their domain because the crocodiles enjoy
> such an advantage in their swampy medium.
Raccoon. Monitor Lizard. And the Nile river isn't "swampy".
> Also, while some guard their
> nests, others lay and forget. This may not have been a luxury afforded
> to eggs which required attention--in other words, if dinos were
> endothermic they must tend their nest. In any case, there is plenty of
> evidence of dino parental investment. This requires many non-stealthy,
> predator-alerting trips to and from the nest!
> Over the Cretaceous, dinosaurs tended to get bigger. The bigger
> you are the harder to hide. Something, maybe basic dinosaur constraints,
> limited their competitive ability in the small animal niche. As the
> Cretaceous wore on, smart, super-stealthy, and reproductively-secure
> mammals may well have made life impossible for big animals seeking
> protection in close cover. What is left? Set up an egg mountain. Lay
> your eggs in some scrubby terrain where not many small things can
> travel. Move to the highlands. Create egg-protecting societies.
> Dinosaurs were increasingly forced to develope strategies of defence
> rather than strategies of stealth. This was expensive. How much better
> to carry your babies away (like mammals), or to hide your eggs in
> out-of-the-way-places such as offshore islands, inaccesible locations
> (like birds and snakes), or to lay and forget (like turtles). Dinosaurs
> made a tremendous gambit for the open-field, big animal niche. And for
> a while (a long while) they were successful. But their life style had a
> fatal flaw: while their body architecture was fit, their reproductive mode
> was not. Too bad they don't award partial credit in evolutionary stakes.
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.
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?
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.
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?
Your idea doesn't even allow for the survival, let alone existence
and diversity, of modern ratite birds.
7) Mosasaurs and plesiosaurs
Was the extinction of their friends the dinosaurs just too much to
bear, so they killed themselves?
8) Catastrophic extinction
The data does not strongly indicate a gradual extinction.
Dinosaurs could have easily been still going strong up
to the final days of the Cretaceous.
Wroblewski's assessments of theropod diversity support this. The
supposedly troubled times of the latest Maastrichtian Western North
American faunas could be due to things like changes in depositional
environment, or an environment less conducive to a diverse herbivore
population (moving from mixed forest and open lands to all open habitat,
for example). Other faunas, such as the Tenontosaurus-Deinonychus fauna,
show similarly low diversity, but this was tens of millions of years
before the dinosaurs went extinct! The American West is incredibly low in
diversity, but this hardly argues that placentals will go extinct any time
in the near future. In addition, we don't know anything
about the latest Cretaceous in other parts of the world. For all we know,
the East coast of NA was still a highly diverse fauna, and we know nothing
about Australia, South America, Asia, etc. etc. etc. Can we even be sure
that Centrosaurines really did go extinct? It seems possible that they
existed in a more restricted range, a range that did not include Western
North America. Catastrophic extinction is further favored because of
9) lack of mammal diversification into dinosaurian niches (i.e. large
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.