Re: Viviparous dinosaurs?

[Crpntr@ix.netcom.com (Kenneth Carpenter)]

Skip Dahlgren wrote:

>I've heard some speculation that certain dinosaurs may have been 
>viviparous.  
>What is the current thinking on egg-laying versus live-bearing 
>dinosaurs, 
>both as a simple matter of means of giving birth and in context of 
>maternal 
>care and family structure?  

There is no proof that any dinosaurs had live birth (ovovipiraous), 
Bakker not withstanding.  The idea was first proposed by OC Marsh in 
1883 for some very small sauropod bones found with the holotype of
Camarasaurus grandis.  However, these bones and those referred by Bakker 
as embryonic Apatosaurus are too large to be embryonic. In addition, the 
bones are better developed than known embryonic dinosaurs.  Bakker's 
arguement that sauropods have wide pelvic canals as "proof" of live 
birth is bogus because no one has yet sexed sauropods, and all sauropods 
know have wide pelvic canals (taphonomic bias towards females? :(>  
These baby sauropods, and those from Oklahoma, are estimated to be about
1.5-2 meters long.



>The latter would certainly be advantageous to a large 
>carnivore, whether social or solitary, whether it gave maternal care 
>or not, since such young most likely would not require a nest or 
>shelter for any significant period of time after birth, and would be 
>better able to travel and feed themselves (or keep up with their 
>mother/family group).  Is there 
>any evidence to support such a hypothesis, and regarding which species? 
> Any info would be appreciated.  :)

Why would it be advantageous for the female to carry around additional 
weight while engaged in a fight with
a prey?  At present, there is no evidence of either larger eggs than the 
16" long ones, or that any dinosaur
gave live birth.  In fact, the continued increase in eggshell diversity 
would agrue otherwise.