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Did non-avian dinosaurs guard nests?
I was wondering where in the range of "Yes, almost certainly." to
"Yes, possibly." does the answer to that question fall?
The evidence that I have read of or deduced is this (and I would really
appreciate it if anyone knows of additional evidence):
1. Nest attendance is known for maiasaura and another dinosaur (Horner).
2. Active brooding is strongly supported for Troodon and Oviraptor
3. All (except for one) avian species tend nests. And most crocodilians
tend nests. Can I say anything here about extant phylogenetic bracketing.
Or can I use this statement as any kind of support?
4. All dino nests found are in sand or possibly vegetation mounds. All
crocodilians that lay eggs in sand also guard their nests. This is to
prevent predation (Coombs). Can one assume, then, that the eggs of big
oviparous creatures are somehow easy to find for their predators? Thsi
being the case, dinosaurs which oviposited in sand would also have to
guard their nest.
5. Crocodilians that make vegetation mounds do not tend their nests. But
megapodes do. This is probably because of the heavier oxygen demand of
avian eggs. Of two equally sized croc _C. porosus_ and _C. niloticus_ the
former oviposits in a veg. mound and has a clutch mass half of the latter.
Dinosaurs, if their eggs had a high metabolic rate would probably have to
stay with the nest to keep it ventilated.
6. Rapid growth rate for dino embryos requires consistent periods at
environmental optima. This can only be maintained with the help of a
parent, either by shading, active brooding, ventilating etc.
Any comments, on or off-line, appreciated.
Thanks, John Bois.