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Re: Psittacosaurus adult found with 34 juveniles




DinoBoyGraphics@aol.com wrote:
>      That being said, unless the babies were born the size of a thimble and 
> had already increased in size 10-fold, it's hard to understand how they could 
> have all come out of one animal.  Maybe extremely delaid incubation and 
> simultaneous hatching could explain it (they were pretty close in size), but 
> it seems more likely that the juveniles were from more than one animal, so my 
> best guess is we are seeing communal nesting.  Ostriches engage in communal 
> parental care, so it doesn't require lots of smarts to pull off.

Both extant birds and some crocodilians (such as caimans) form juvenile
creches made up of offspring from several parents. With a phylogenetic
bracket like that, it wouldn't be a surprise if other (extinct)
archosaurs did also.

I've often wondered whether the Lark Quarry trackway in Queensland may
have been caused by an adult theropod taking a large creche down to the
water to drink, where the juveniles saw and chased a flock of small
ornithopods (it would explain why small theropod prints wind up inside
the prints of the large theropod - they could have been following
closely).

Ostriches are an interesting example, as each pair will attempt to drive
off other pairs and claim their hatchlings as their own. A really
agressive pair may end up with over a hundred chicks to look after. The
theory is that the parents benefit by having their own offspring
protected by the sheer number of other chicks around them. The chicks
benefit by having a very agressive and dedicated pair of adults to
supervise them.

The fact that males will mate with multiple females, and that females
themselves will allow multiple males to mate with them, complicates
matters further. There is always the chance that any single male will be
protecting babies that have no genetic relationship to him what-so-ever.
However by spreading the genes around, no single animals risks putting
all it's eggs in one basket (an appropriate metaphor!)

-- 
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Dann Pigdon
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://heretichides.ravencommunity.net/
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