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John Bois wrote:
> Jim Kirkland,_Dinosaur Eggs and Babies_ paper.
> You say that dinosaurs were able to withstand millions of
> years of egg predation and ask, in different words: What, then,
> could have changed towards the K/T to cause extinction via this
> I claim new mammal and bird species may have had an
> influence here.
> You say: "Although both _Gobiconodon_ and _Didelphodon_ were
> large enough (cat-size) and physically capable of eating dinosaur
> eggs, there is no evidence of this having taken place."
Gobiconodon is early Cret. Also remember at cat sized that means they
could eat small eggs some were as big as melons.
> 1. Mammals are smarter and generally more behaviorally talented
> Cretaceous mammals were not very smart, Troodon would have been much
smarter. Mammals got smarter over time.
> 2. Mammal nest attack (if it happened) might have occurred in a
> relatively narrow evolutionary time period. This lowers the
> likelihood of any being found.
So do varanid lizards.
> 3. I think mammal bones don't fossilize as well as dinosaur
In Mogollia everything has a equal chance. We find lots of perfect
mammal fossils. By the way in the Jurassic mammals were as diverse and
more abundant than dinosaurs.
> By the way, I once read of Andrew's expedition that they pulled
> (Zalambdalestes?) skulls out of dino nest beds (protoceratops?).
> Has anything more been said about that?
The skull would have been about 1/25 - 1/50 the size of a egg. Several
Zalanbdalestes would fit in one Oviraptor "proto" (smarter than
Cret. mammals) egg.
> 4. We haven't yet found all mammalian contenders.
I seriously doubt we've missed any large relatively common mammals. We
screen wash and get hundreds to 10,000 of tiny mammal teeth. All you
need is one tooth to ID a mammal.
> You say: "Because most, if not all, dinosaurs, probably buried
> their eggs to at least some degree...raiders of dinosaur nests
> would have to have the ability to dig open the nest. Such an
> ability is unlikely for most...birds."
> First of all, I think it likely that birds took a terrible toll
> on hatchlings. Like Marshall eagles which today snatch ostrich
> chicks from under their parents' beaks, pre K/T birds may have
> decimated dino babies.
There is not much evidence for large birds in the late Cretaceous, But I
agree this is negative evidence.
> You say: "There was ground cover at many Mesozoic sites as
> indicated by densely and finely rooted paleosoils. In many cases
> it was ferns."
> But ferns have flagellated sperm and require water to reproduce.
> They are (today, anyway) usually restricted to damp environments.
> Faunal density is higher in these environments. This is not
> analogous to desert margins and savannah.
My belief is that arid env. ground cover was made up of dry adapted
opportunistic ferns as in the Jurassic Morrison "Dry - seasonal" there
are no known plants but ferns that could have given us these root traces
in the arid carbonate-rich, soils. The Morrison has a great diversity of
nonflowering plants based on pollen and spores. The ground cover
Jurassic plants (extinct) were displaced by angiosperms (much better
Savannah and desert plants. Flowering plants make better desert plants.
Remember the resurection plant (a club moss) is abundant
throughout the Chichichuan desert of Mexico. It waits for a rare rain
and trys to reproduce get those gamets to swim to another plant.
I drive botanists nuts but I cannot find anyother way to come up
with enough plants to feed all the animals in the Morrison. Most
gymnosperms do not take grazing well.