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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