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RE: sauropod breeding



> I'd like to ask the other people on the list how likely some of my
ideas about sauropod breeding

I'm all for it ;-)


Kenneth Carpenter, Ph.D.
Curator of Lower Vertebrate Paleontology/
Chief Preparator
Department of Earth Sciences
Denver Museum of Nature & Science
2001 Colorado Blvd.
Denver, CO 80205
 
Phone: 303-370-6392
Fax: 303-331-6492

for PDFs of some of my publications, as well as information of the Cedar
Mountain Project: 
https://scientists.dmns.org/sites/kencarpenter/default.aspx
++++++++++++++++++

-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu] On Behalf
Of Brian Lauret
Sent: Sunday, March 12, 2006 11:45 AM
To: dinosaur@usc.edu
Subject: sauropod breeding

Dear all,

I'd like to ask the other people on the list how likely some of my ideas
about sauropod breeding are to be true or at least realistic. For
purpose of illustration the example I'm using is the Morrison fauna.

I used to think WWD was off when they proposed Diplodocus females laid
their eggs and left them after that. Undoubtedly inspired by the
assumptions about parental care in dinosaurs, I felt Diplodocus would
have practised at least some parental care. Thinking the whole matter
over however, made me reconsider that belief. It would have been
impossible for an adult Diplodocus to look after its eggs or offspring.
I've come to think the whole WWD dinosaurs might have been quite
feasible,though the youngsters might not have taken as long to grow as
the WWD Diplodocus did.

As shown in WWD, infant mortality would have been extremely high. In
reality, the number of predators would have been even higher. Not only
would Ornitholestes and Allosaurus have been present, but we also have
Coelurus,'Beleemosaurus' (sic?),Tanycolagreus, Koparion, Stokesosaurus,
Avetyrannus, Ceratosaurus, ?Elaphrosaurus, Marshosaurus,Torvosaurus and
Saurophaganax as potential predators, as well as
crocodiles,lizards,rhynchocephalians and perhaps mammals and the
occasional avialean. Add to that all kinds of other hazards and it seems
surprising any of the little ones ever became adult. Especially
considering the fact we seem to be dealing with (comparitively) small
creatures without spikes,clubs,speed or any other obvious weapons or
defenses.

The fact that infant mortality must have been very high makes me think
that not only numerous nests were laid by female sauropods at once, but
also that this must have occured very regularly, if only to replenish
numbers. 
Considering the fact sauropod eggs were very small compared to female
body size and that after being laid,neither eggs nor youngsters require
any help from the adult, or at least don't receive it, i think it would
have been possible or even neccesary for a female to lay often, perhaps
even every year.

This would have meant there was a presence of reasonable to large
numbers of young Diplodoci of various stages of development at any given
time. Perhaps the presence of so many theropods at once can be partially
attributed to this fact. In fact, I've been considering Ornitholestes as
a possible young sauropod specialist. After all, we seem to be dealing
with a small but robust theropod that does not seem to have been much of
a cursor. (Or at least,that's what I've read about the beastie.) Young
sauropods would have been small and probably not very fast. Could it be
possible Ornitholestes' 
main prey consisted of very small sauropods, or that they at least
constituted an important part of its diet? Its robust build would seem
to indicate it was used to killing prey too large to be consumed whole
and required some more power to tackle.

I'd suspect the few Diplodocus to survive to sexual maturity and
reasonable size would have joined the others at the moment they did. Or
perhaps infant groups stayed together as a herd for all their life. To
prevent inbreeding or for other reasons males might have been ousted
from the group at that point and might have had to lead a solitary life
or in small groups with related males. It would seem realistic to me if
male sauropods were only allowed close to the herd in the breeding
season.

Are any of these thoughts reasonable or are there reasons why they are
unlikely to be true?

Thanks in advance,

Brian