Posts Tagged 'sauropods'



Sauropod necks – what were they for?

Long time readers might well recall that for a few years I was a volunteer at London Zoo where I worked on what was the Cotton Terraces (now sadly rebranded as the “Africa Zone”) with various hoofstock and ungulates. It was, generally, an absolute joy and I learned a great deal about animal management and animals in general. Among my occasional charges were the giraffe and I have a long and abiding affection for them from my time there. This has in part manifested itself by my keeping up with giraffe research in the literature and when an opportunity arose to write about giraffes and dinosaurs, well, I could hardly resist.

So what do giraffes and dinosaurs have in common? Well not much to be honest, but perhaps inevitably the long necks of giraffe have been brought up a number of times in the past as analogues for the long necks of sauropods. It’s not unreasonable really as good analogues are important for inferring the functions and behaviours of extinct taxa and there are very few terrestrial long-necked herbivores out there, and even less that look even vaguely like sauropods. So the high reach of giraffes has been used to suggest sauropods reached high into the trees to feed.

Male giraffe sparring at Beijing zoo.

Set against this background has more recently been the controversy over sauropod neck postures and quite how much (or even if) they could raise their heads and necks. But it gets more complicated still (yay!). Back in the mid 1990s it was suggested that actually giraffe necks hadn’t evolved for feeding high in trees, but instead were sexually selected structures. Perhaps not surprisingly, the same hypothesis was then extended onto sauropods too! If they couldn’t raise their necks up, and the only obvious living example (in giraffes) was only an opportunistically high browser, then maybe sauropod necks were the result of sexual selection too? (Mike Taylor has a preview of these ideas here).

In a new paper out today myself and the SV-POW! boys (Messers [or rather, Doctors] Taylor, Wedel and Naish) take on this idea. The detail is of course in the paper but there are several interlinked threads to this paper that affect different lines of sauropod research and ecology. Perhaps most interestingly for me is the work on giraffes though, since actually the idea of sexual selection in these beautiful artiodactyls is far weaker than originally proposed and actually high browsing does seem to be the primary function of the neck.

Sauropod neck lengths. From Taylor et al. in press

Thus the original analogy can be restored and the analogy for sauropods having sexually selected necks rather falls by the wayside. Couple that with the existing work by my colleagues on the potential vertical reach of sauropods and another barrier falls by the wayside. Even if sauropods couldn’t reach high into trees though, that’s not necessarily a barrier to their long necks being adapted for feeding efficiency. Anyone who as seen a grazing goose will recognise their feeding pattern with the body of the bird only plodding along slowly but the long neck sweeping from side to side so that for every step forward (a big deal of effort for a 50 ton sauropod say) a fair area of new grass can be covered by the head. In short, a long neck can be efficient whether you are reaching up or not.

All together (and there is obviously more to this than I’m covering briefly here) we find no convincing evidence of sexual selection going on in sauropod necks and are satisfied that the long necks would have provided a significant horizontal and vertical reach and thus did afford a significant part of their feeding ecology. There’s no good evidence (at the moment, at least) that any sauropod necks were under sexual selection or indeed, that those of giraffes were. That doesn’t mean it wasn’t happening, but there is nothing to suggest it was.

This must, of course be hedged with a couple of most important and basic caveats to these kinds of papers. Critically is that of multifunctionality – that structures can have more than one function, so there could be some cryptic sexual selection ongoing alongside feeding advantages. Though as it happens in this case, it’s this very issue that helps us deal with some of the evidence for sexual selection. Secondly of course this paper is a review – we talk about general patterns and trends and evidence. We do not look at all sauropods in great detail and while we have great confidence in the findings of our paper we are talking about generalities – there is of course a reasonable chance that something was an exception.

Taylor, M.T., Hone, D.W.E., Wedel, M.J. & Naish, D. The long necks of sauropods did not evolve primarily through sexual selection. Journal of Zoology, in press.

Mamenchisaurus ungual

Having mentioned the other day the sheer size of some sauropod claws, it seemed long overdue that I drag out this photo from about five years ago. It’s an ungual of that great long-necked beast Mamenchisaurus. Unfortunately I don’t have with me any of the shots that would put this close-up in context so I’m not sure if it’s a manual or pes one, though memory tells me it’s in the hand. Regardless the two key issues are relate to it’s dimensions.

First of all, it’s big. Really quite big. OK, so this is a very large animal (this individual was around 15 m as I recall) but even so, that claw is getting on for some 20 cm in length. That’s pretty huge, even in context. Secondly, it’s also big compared to the phalanx it articulates with. Given how sauropod hands and feet are built, you can’t imagine that this ever really had to swing around on that joint but instead poked out of a fleshy foot. Yet it’s nearly twice the height of it’s articulating phalanx so it’s hard to imagine that the claw is just big as some kind of evolutionary hangover, but was actively being selected or maintained at this big size, despite its discrepancy with the rest of the foot. In short, yeah, that’s pretty huge.

Spiky sauropods

Today’s image comes courtesy of Phil Mannion and something he sent me for his guest post a while back on sauropod diversity. It never got used and has been sat in my files till I cam across it of late and decided to drag it out and give it an airing. It shows off the bizarre South American sauropod Amargasaurus.

This is, justifiably, famous for its groovy spines that extend as a pair of rows along the neck. This calls to mind, if on a smaller scale and rather different form, other ‘crested’ dinosaurs like Ouranosaurus. Much as I do like these, it’s also well worth talking about the fact that this is also one of a rather rare group of sauropods called dicraeosaurids. These are rather few and far between with Amargasaurus and Brachytrachelopan from South America and the eponymous Dicraeosaurus from Tanzania. All three have rather tall and oddly shaped necked vertebrae though obviously this one takes the crown, but more interestingly, they all have very short necks and are relatively small taxa.

Short (or at least relatively short) necked sauropods are turning up in increasing numbers though they’re still somewhat rare and the classic body plan of sauropods of a big body with a long neck and tail is hardly in danger, even if the dicraeosaurs are doing their best to challenge this. Long necks have an especially important place in sauropod evolution of course, and I’ll be writing more about that in the next couple of weeks. Stay tuned!

Guest post: Grazing giants – sauropod feeding

In today’s guest post, John Whitlock takes us through his recent PLoS One paper on the wear facets of sauropod teeth and what this might mean for their feeding habits. I’ve long had a general curiosity about this and was delighted to see renewed interest in this area, not least from someone who takes their sci-comms seriously enough to have signed up for AAB! Take it away please John:

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Introducing Brontomerus

This is really just a quick post because all the action is of course going down at SV-POW. Yes there is a new sauropod on the block and the SV-POW boys, or at least Mike Taylor and Matt Wedel, are in part responsible. So inevitably you can get all the real details there and I am in this case, little more than the messenger.

Still, it’s always nice to talk about a new taxon and I’m sure this guy, named Brontomerus, will be in the news and blogosphere if only for the name. It shares a large part, rather obviously, with the defunct ‘Brontosaurus’ and that I’m sure will go down well. But this is not a thunder-lizard, but a thunder-thighs. Yes, them named it for having, for want of a better phrase, fat legs. It has more going for it than that of course but for the real skinny, hop on over there and take a gander at the first of what could be quite a long series of posts. And watch out for the inevitable avalanche of inaccurate references to Brontosaurus in the media.

Brontomerus life reconstruction. Courtesy of F. Gascó.

All at sea

Sauropod fans will probably be regular readers of SV-POW! and might have spotted the recent posts here and here on the sort-of-but-not-quite paper by a group working on some privately collected material. There are all kinds of issues about the rights and wrongs of collecting material like this and producing papers on material that is privately held and indeed a paper that is privately published and apparently un-reviewed. All of this aside (and not that it is not important) for me the real issue is the proposal in the manuscript that pretty much every sauropod in the Morrison (thinks like Amphicoelias, Diplodocus, Apatosaurus and many others) are ALL just a single species.

Now this is perhaps silly at best, and what it does (if this paper gets published) is create as huge problem that simply should not exist. As I have said repeatedly on here, publishing a paper is about style and attitude, not qualifications. However, inevitably, those people without formal training (or a limited amount) in academia and palaeontology are more likely to make bigger mistakes.

Issues of all kinds, but especially taxonomic ones, can be a massive headache for mainstream research. Such problems are incredibly easy to create and very hard to fix. One solution (often adopted by those wishing to skirt around such papers) is to simply ignore it. Don’t refer to the work or cite it (or at least the problematic issues). I don’t like this as it is, I think, intellectually dishonest to ignore the work when you know it exists (however bad, or complex). The alternative is though, I admit, little better. To fix these problems can involve the creation of a long and difficult paper which will take a huge amount of time but achieve little other than restoring the status quo. Whichever person ends up taking on the responsibility will lose quality research time to get back to the status quo and produce something that few people will read or cite.

Take the example here, assuming it is published with the ideas as stated. One would have to establish that the new taxon is not synonymous with every other sauropod in the Morrison and  reestablish all the existing genera and demonstrate that these are genuine and not just the result of variation or sexual dimorphism or ontogeny. Obviously much of this has gone before, but restating it the context of a new taxon makes it awkward and it’s all utterly unnecessary.

This is not to pick on the paper in question (enough people are doing that) but to make a point. Science is there to make progress and create understanding. There are ways of doing this from dabbling in the shallows to diving deep where far from land. However, one should work from one to the other. Picking your spot and hurling yourself out into the unknown without the requisite experience or training means those that have it have to come and rescue you and one should not be surprised if they find the job onerous, unnecessary, tedious and annoying. They want to explore the depths of understanding, not try and drag your embarrassing mess back shore and throw it up on the beach so it can’t bother the others. It’s not their job, but they’ll do it. But you are wasting their time if they do save you, and cluttering the view with your rubbish if they just let it sink to the bottom.

The obvious solution? Don’t do it. Just because it looks fun and easy doesn’t mean that it is and learning that will make it better for everyone. Sadly I can cite a few examples of people whose only response to this kind of this is to jump back in even further out than last time but hopefully a few might learn the lessons of others and take the steps to get it right having seen this one flounder.

Guest post: dishing the dirt on dwarfing in dinosaurs

A couple of weeks ago a new paper came out of sauropod bone microstructure in sauropods, the latest in a series from the Bonn lab of Martin Sander. The lead author, Koen Stein is yet another ex-Bristolian who is now pursuing a PhD and here takes time out of the traditional student panic to write a bit about the growth of the dwarf dinosaur Magyrosaurus.

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Guest post: sauropod diversity over time

Phil Mannion and his pet dino.

PhD student Phil Mannion guests this time out on the Musings. Phil works on sauropods and has just had a new paper published looking at their fossil record and diversity over time. Do they really reach a peak of diversity in the Jurassic, or is this just a bias from how complete the specimens are from that time? Read onto find out more:

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Diplodocus skull

This time out, it’s a rather nice cast of a Diplodocus skull at the IVPP. However, it’s mounted on the end of a Mamenchisaurus skeleton which rather reduced the impact.

Still, that’s not as bad as it sounds, for a very long time there was confusion and disagreement about what sort of sauropods were and although there were quite a few specimens known, no Mamenchisaurus had been recovered with anything like a decent skull. Thus not only did we not know what kind of skull they had, it was hard to guess what kind of skull they might have had since their immediate relatives were not known. As a result, you can see a Diplodocus, Shunosaurus or even Apatosaurus skull attached onto a Mamenchisaurus skeleton in various Chinese museums. Since they don’t always have the money to replace them, these things tend to hang around (and replacing a skull on the end of a 10+ m neck is no mean feat either) it’s perhaps no surprise, though can look a bit odd to those who know better.

Those who aren’t in the know will be pleased to find out that in 2002 a very complete and well preserved Mamenchisaurus was described complete with an intact skull. This looks, superficially at least, like those of brachiosaurs with a nice big internarial bar that arches off the top of the skull.

Guest post: A brand new brachiosaur

L-R Jeff Wilson, Dan Chure & Brooks Britt. Image courtesy of BYU.

One of the few sauropods I am in anyway familiar with is Giraffatitan (formerly Brachiosaurus) and as a result I have developed more of an interest in the brachiosaurs than other sauropods. I was excited to learn that a new taxon had recently been unearthed and described and, against the odds, there’s good skull material. Lead author on the study, Dan Chure, was gracious enough to put together a guest blog post on the subject and here is it:

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Bellusaurus

Continuing the quite long series of short posts covering all manner of IVPP material we have the very little studied and perhaps even more rarely seen Bellusaurus. Pictured is one of two mounts at the IVPP, though neither are great and the bones are largely obscured.

Bellusaurus is known from the Middle Jurassic and comes from western China in the area that I have so far yet to visit as part of my field seasons in China due to various permit problems. There are apparently quite a few specimens known, though I’ve not come across any in our main collections (not that I have gone looking) though at least there are bits of two on display which is more than I can say for the amount of information available in the literature which seems conspicuous by its absence.

The animals are clearly small (about 4m in total length) and have been suggested to be juveniles by people who a) know sauropods much better than me and b) have seen the material. Still, I couldn’t spot any obvious indicators of them being youngsters on the admittedly poor mounts, so I’d suggest that it’s at least possible that this is, if not an adult size, close to it. There are other sauropods out there that are closer to this is size so it’d be a surprise, but not a shock.

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Sauropod tails: up or down?

By now even the media (well most of it) has cottoned onto the fact that sauropods did not drag their tails along the ground like giant lizards, but instead held them off the ground behind them. Except, well, not quite always.

While sauropod footprints are common, there are the occasional set of tracks that also show a mark that is interpreted as (and can only really be) that left by a tail dragging on the ground behind. So what’s going on, is the tail up or down?
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