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Re: Differential reproductive failure of dinosaurs



John Bois makes some very good points in his latest response.  However, I 
would like to make a few points myself:

1)  Yes, placental mammals take better care of individual offspring, but 
not without costs.  One is the considerable burden placed on the mother, 
and the other, related, is the fact that placental mammals cannot produce 
as many offspring at a time as could the dinosaurs.  I think the strong 
and weak points of their strategies most likely offset, and neither 
enjoyed much differential reproductive success over the other.

2)  Hmm...  The relative failure of ratites couldn't have anything to do 
with the lack of niches for large, armless bipeds, could it?

3)  Yes, dinosaur nests faced many dangers, but they had faced those 
exact same dangers for 150 Ma before the K/T.  I maintain that the 
situation of dinosaurs vs. egg predators remained _status quo_ 
throughout the Mesozoic.  I see no evidence that the lizards, snakes, 
mammals, and birds at the K/T boundary suddenly became much better at 
eating non-avian dinosaur eggs, or even that they were appreciably better 
at doing so than the pterosaurs, lizards, rhynchocephalians, small 
non-mammalian therapsids, and other groups around at the beginning of the 
dinosaur age.  That has been my main point all along.

Nick Pharris
Pacific Lutheran University
Tacoma, WA 98447
(206)535-8206
PharriNJ@PLU.edu