Armored Little Sauropods

31 07 2007

Update: Julia, at my request, has written up her own take on the poster. We’re both looking forward to when the research comes out in full.

When I think of sauropod dinosaurs, the first images to come to mind are of the “classic” sort; relatively smooth-skinned, elephantine beasts whose tails are so long that they almost appear to be out of sight, moving in a small group through near a woodland (Mark Hallett’s “The Long March” being one of my favorites). Indeed, sometimes it’s easy to forget that all those behemoths started out as surprisingly small babies, and some of those babies may have had an armor coating. It’s been known for some time now that some sauropod dinosaurs had bony osteoderms covering their bodies, although the bony fixtures seem to be far too small and too far apart to have acted as an effective defense against predators. Saltasaurus is one of the better known titanosaurs to posses scutes, and although it is sometimes depicted as having a turtle-like shell, there doesn’t seem to be anything to corroborate this. Nevertheless, the osteoderms may have provided some protection for the dinosaur, not when fully grown, but as a baby.

Although it appears in a journal that does not require peer review (Nature Precedings), a new paper (although it’s really more of an abstract) entitled “Functional aspects of titanosaur osteoderms” by Thiago da Silva Marinho suggests that the growth patterns of titanosaurs might have something to do with the function of the osteoderms. Given that some titanosaur embryos seem to show “tuberosities” on the skin in a row along the back and “rossettes” of a larger tuberosity with smaller ones surrounding it. While these are not the actual osteoderms, they seem to be the place where the osteoderms would be developing (the stage of development in which the embryo was fossilized probably makes a difference here), and if this trend continued it would seem that some newborn titanosaurs would have a set of bony scutes along their back. As they grew up, the scutes would move further and further apart, having little function. If given enough evolutionary time, I wonder if such patterns could have led to more armored sauropods, although there is obviously no way to prove such a pattern now.

In any case, it seems that Marinho has recognized a real pattern, but what use the scutes were is still open to hypothesis. The paper states that such armor would have been of use against small predators, but the neck and underside of the young would still seem to be relatively vulnerable to attack. Perhaps the osteoderm pattern was a response to insects or parasites, discouraging pests from attacking/attaching themselves to the young dinosaurs (when pest, parasites, and biting insects could have possibly been more of a danger). Regardless of the cause, something seems to have selected to protect the dorsal surface of these young dinosaurs, and hopefully more careful study on the subject will be undertaken.

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2 responses

1 08 2007
Thiago da Silva Marinho

Thanks for your interest in my work (in progress as you noted; I should finish the manuscript until the end of the year).
If you would like any information about this work and others by myself and the group I am into, just let me know.
My best regards,

Thiago

29 03 2010
jeehaan

Hi, I was wondering where can I find the article/book “functional aspects of titanosaur osteoderms” I googled it and all I found was a one page slide.

Thanks in advance
Jeehaan

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