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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.
Pacific Lutheran University
Tacoma, WA 98447