Spinosaurus News ~

[DinoFan83]

Quote:I think the limitation with the crocodile comparison is the discrepancy in the neck. The crocodile has a much shorter and less mobile neck than Spinosaurus looking at the anatomy. With its long and seemingly flexible neck, I wonder if the body of Spinosaurus was underwater while it kept its head up to breathe as needed.

You make a fair enough point. I do think the using the neck alone as the point of flotation would be useful for breathing assuming there were airsacs.

Quote:Whatever animal those cervical vertabrae are from, is it correct to infer they would be surrounded by some type of air sac based on this study?

I believe so, yes. However, the airsacs in question on those cervicals wouldn't have been very numerous in the first place given the relative paucity of attachment spots for them compared to animals like Aerosteon (in the study you linked).

Quote:If Spinosaurus was rather thin in the chest (please correct me if not, but I recall thin vertebra on Spinosaurus, which I am inferring to mean a lack of chest girth) and the thoracic vertebrae lacked pneumatization, it does not seem it had (space for) much lung/air sacs without sacrificing diving capability. 

I don't think it's necessarily just the width of the animal we should be looking at, but also the overall shape. While Spinosaurus wasn't exactly thin in its chest (as you may remember reading about in the discussion on the Henderson et al. model a few pages back), it does not seem to me as though it would have been able to have a lot of lung or airsac space without having to worry about its buoyancy given the shape of its thoracic region.
The reason for this being that birds as well as non-avian theropods with a lot of pneumatization (for example, tyrannosauroids like Aerosteon) have a very different thorax shape. As we can see in, for example, GetAwayTrike's skeletals, the highly pneumatic Aerosteon has a short and deep torso for its size compared to Spinosaurus, and so do all modern birds. 
And that makes sense - a sausage-like Spinosaurus is going to greatly inconvenience itself when it tries to inflate/deflate airsacs throughout that stretched out torso because it would take quite a while to get air sufficiently in and out of the airsacs given that the air must literally go on the longest route possible to get in and out of all those airsacs. Not to mention if it can't empty them out sufficiently, it faces buoyancy problems.
TL.DR: The thorax in Spinosaurus is not at all what we see in animals with many airsacs and having them in such a thorax shape would be generally detrimental given how the airsacs work, so I think you are correct that there does not seem to be sufficient space for airsacs without it having to worry about how well it could dive.

Quote:I've never really delved into avian/theropod anatomy so please make all the corrections needed.

No problem. Any inquiries you may have, I will answer to the best of my ability. Reply