Re: T. rex eggs and brooding

[Phillip Bigelow <n8010095@henson.cc.wwu.edu>]

I wrote:
>>  In Montana, alleged eggs of Troodontids also were laid in a linear 
>>row.>So does this tell us anything about brooding behavior in the 
>>Tyrannosauridae >and the Troodontidae? Could these theropods be 
engaged >>in "drop 'em and >forget 'em" egg-laying?  Does this indicate 
that T. >>rex chicks were deadly >12-inch terrors right after hatching 
(requiring >>no matriarchal or patriarchal >care-taking)? And if 
Oviraptor chicks >>required parental care-taking in a >nest, what was 
unusual about the >>Tyrannisauridae and Troodontidae chicks >such that 
they didn't need a >>nest?

Tom Holtz wrote:
>The null hypothesis, on phylogenetic basis, is that all dinosaurs used 
>some degree of parental care, as both the in-group (birds) and the 
>closest surviving outgroup (crocodillians) protect the nest and the 
>young for some duration.


Ken Carpenter responded:
>Megapode birds care for the nest to maintain proper incubation 
>temperature, however, once the young are hatched, there is no parental 
>care.  Therefore, a blanket statement that there must have been some 
>degree of parental care in dinosaurs is not necessarily true.

  I think that body-incubation, sensu stricto, is a likely possibility in 
Dinosauria, based on parsimony.  However, the great differences in the egg
_laying_ style of dinosaurs suggests that nest-building was not a shared
character in the group.  The purported Montana Troodon eggs, and the alleged
T. bataar eggs don't fit a "nest-laying" morphology (unless the theropods
scratched a trench in the ground and layed the eggs---then that may be
considered a "nest" of sorts).  Horner's Maiasaur nests were relatively
high-walled, possibly to keep the chicks in the nest.  This promotes a
home-base of sorts during the nesting period.  The Troodon egg rows, on the
other hand, encouraged the chicks to leave the home-base as soon as they
hatched; there are no physical earthen barriers to keep the chicks
corraled.  The Troodon babies were either: 1) hunting on their own as soon
as they hatched (sort of like baby snakes do today) or; 2) they were running
and hunting alongside mom and/or dad as soon as they hatched. In other
words, Troodon babies may have been pack hunters straight out of the shell.
   If those Chinese eggs are in fact Tyrannosaurid, it shows how disparate
the Mother-child size differences were for this group.  A  1 ft. hatchling
and a 40 foot-long mother must be one of the greatest ontogenetic ranges in
the animal kingdom.  If mother T. rex's did care for their young, they would
have had toe nails larger than their children.  If the T. rex hatchlings
were "planted" in one spot shortly after hatching, then one of the parents
_had_ to bring meat back to the infants.  But without a nest-structure to
keep the chicks in place, there may not be any babies around to feed after
the hunting parent returns with the food.  Maybe the chicks just wandered
off after hatching and ate snakes, insects and warm-fuzzies until they got
bigger?