I was lucky enough to have Phil Mannion as one of the peer-reviewers for my recent paper (Taylor 2018) showing that Xenoposeidon is a rebbachisaurid. During that process, we got into a collegial disagreement about one of the autapomorphies that I proposed in the revised diagnosis: “Neural arch slopes anteriorly 30°–35° relative to the vertical”. (This same character was also in the original Xenoposeidon paper (Taylor and Naish 2007), in the slightly more assertive form “neural arch slopes anteriorly 35 degrees relative to the vertical”: the softening to “30°–35°” in the newer paper was one of the outcomes of the peer-review.)

The reason this is interesting is because the slope of the neural arch is measured relative to the vertical, which of course is 90˚ from the horizontal — but Phil’s comments (Mannion 2018) pushed me to ask myself for the first time: what actually is “horizontal”? We all assume we know horizontality when we see it, but what precisely do we mean by it?

Three notions of “horizontal”

The idiosyncratic best-preserved caudal vertebra of the Snowmass Haplocanthosaurus MWC 8028, illustrating three different versions of “horizontal”. A. horizontality defined by vertical orientation of the posterior articular surface. B. horizontality defined by horizontal orientation of the roof of the neural canal (in this case, rotated 24˚ clockwise relative to A). C. horizontality defined by optimal articulation of two instances of the vertebra, oriented such the a line joining the same point of both instances is horizontal (in this case, rotated 17˚ clockwise relative to A). Red lines indicate exact orthogonality according to the specified criteria. Green line indicate similar but diverging orientations: that of the not-quite-vertical anterior articular surface (A) and of the not-quite-horizontal base of the neural canal (B).

There are at least three candidate definitions, which we can see yield noticeably different orientations in the case of the Snowmass Haplocanthosaurus vertebra that Matt’s been playing with so much recently.

Definition A: articular surfaces vertical

In part A, I show maybe the simplest — or, at least, the one that is easiest to establish for most vertebrae. So long as you have a reasonably intact articular surface, just rotate the vertebra until that surface is vertical. If, as is often the case, the surface is not flat but concave or convex, then ensure the top and bottom of the surface are vertically aligned. This has the advantage of being easy to do — it’s what I did with Xenoposeidon — but it conceals complexities. Most obviously, what to do when the anterior and posterior articular surfaces are not parallel, in the 7th cervical vertebra of a giraffe?

Cervical vertebra 7 of Giraffa camelopardalis FMNH 34426, in left lateral view. Note that the centrum is heavily “keystoned” so that the anterior and posterior articular surfaces are 15-20˚ away from being parallel.

Another difficulty with this interpretation of horizontality is that it can make the neural canal jagged. Consider a sequence of vertebrae oriented as in part A, all at the same height: the neural canal would rise upwards along the length of each vertebra, before plunging down again on transitioning from the front of one to the back of the next. This is not something we would expect to see in a living animal: see for example the straight line of the neural canal in our hemisected horse head(*).

Definition B: neural canal horizontal

Which leads us to the second part of the illustration above. This time, the vertebra is oriented so that the roof of the neural canal is horizontal, which gives us a straight neural canal. Nice and simple, except …

Well, how do we define what’s horizontal for the neural canal? As the Haplocanthosaurus vertebra shows nicely, the canal is not always a nice, neat tube. In this vertebra, the floor is nowhere near straight, but dishes down deeply — which is why I used to the roof, rather than the floor of the canal. Rather arbitrary, I admit — especially as it’s often easier to locate the floor of the canal, as the anterior margin is often confluent with fossae anteriorly, posteriorly or both.

And as we can see, it makes a difference which we choose. The green line in Part B of the illustration above shows the closest thing to “horizontal” as it would be defined by the ventral margin of the neural canal — a straight line ignoring the depression and joining the anteriormost and posteriormost parts of the base of the canal. As you can see, it’s at a significantly different angle from the red line — about 6.5˚ out.

And then you have human vertebrae, where the dorsal margin of the neural canal is so convex in lateral view that you really can’t say where the anteriormost or posteriormost point is.

Left sides of hemisected human thoracic vertebrae, medial view. Note how ill-defined the dorsal margin of the neural canal is.

So can we do better? Can we find a definition of “horizontal” that’s not dependent of over-interpreting a single part of the vertebra?

Definition C: same points at same height in consecutive vertebrae

I’ve come to prefer a definition of horizontal that uses the whole vertebra — partly in the hope that it’s less vulnerable to yielding a distorted result when the vertebra is damaged. With this approach, shown in part C of the illustration above, we use two identical instances of the vertebrae, articulate them together as well as we can, then so orient them that the two vertebrae are level — that a line drawn between any point on one vertebra and its corresponding point on the other is horizontal. We can define that attitude of the vertebra as being horizontal.

Note that, while we use two “copies” of the vertebra in this method, we are nevertheless determining the horizontality of a single vertebra in isolation: we don’t need a sequence of consecutive vertebrae to have been preserved, in fact it doesn’t help if we do have them.

One practical advantage of this definition is that its unambiguous as regards what part of the vertebra is used: all of it; or any point on it, at the measurement stage. By contrast, method A requires us to choose whether to use the anterior or posterior articular surface, and method B requires a choice of the roof or floor of the neural canal.

Discussion

I have three questions, and would welcome any thoughts:

  1. Which of these definitions do you prefer, and why?
  2. Can you think of any other definitions that I missed?
  3. Does anyone know of any previous attempts to formalise this? Is it a solved problem, and Matt and I somehow missed it?

Answers in the comments, please!

References

(*) Yes, of course we have a hemisected horse head. What do you think we are, savages?

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I got an email a couple of days ago from Maija Karala, asking me a question I’d not come across before (among several other questions): how much poop did Argentinosaurus produce in a day?

I don’t recall this question having been addressed in the literature, though if anyone knows different please shout. Having thought about it a little, I sent the following really really vague and hand-wavy response.

Suppose Argentinosaurus massed 73 tonnes (Mazzetta et al. 2004). In cattle, food intake varies roughly with body mass to the power 0.7 (Taylor et al. 1986), so let’s assume that the same is true of sauropods.

Let’s also assume that sauropods are like scaled-up elephants, in that both would have subsisted on low-quality forage. Wikipedia says elephants “can consume as much as 150 kg (330 lb) of food and 40 L (11 US gal) of water in a day.” Let’s assume that the “as much as” suggests we’re talking about a big elephant here, maybe 6 tonnes. So Argentinosaurus is 73/6 = 12 times as heavy, which means its food intake would be 12 ^ 0.7 = 5.7 times as much. That’s 850 kg per day.

Hummel et al. (2008, table 1) show that for a range of foods, the indigestible “neutral detergent fibre” makes up something around half of the mass, so let’s assume that’s the bulk of what gets pooped out, and halve the input to get about 400 kg of poop per day.

References

  • Hummel, Jürgen, Carole T. Gee, Karl-Heinz Südekum, P. Martin Sander, Gunther Nogge and Marcus Clauss. 2008. In vitro digestibility of fern and gymnosperm foliage: implications for sauropod feeding ecology and diet selection. Proceedings of the Royal Society B, 275:1015-1021. doi:10.1098/rspb.2007.1728
  • Mazzetta, Gerardo V., Per Christiansen and Richard A. Farina. 2004. Giants and Bizarres: Body Size of Some Southern South American Cretaceous Dinosaurs. Historical Biology 2004:1-13.
  • Taylor, C. S., A. J. Moore and R. B. Thiessen. 1986. Voluntary food intake in relation to body weight among British breeds of cattle. Animal Science 42(1):11-18.

You could drive several trucks through the holes in that reasoning, but it’s a start. Can anyone help to refine the reasoning, improve the references, and get a better estimate?

I have before me the reviews for a submission of mine, and the handling editor has provided an additional stipulation:

Authority and date should be provided for each species-level taxon at first mention. Please ensure that the nominal authority is also included in the reference list.

In other words, the first time I mention Diplodocus, I should say “Diplodocus Marsh 1878″; and I should add the corresponding reference to my bibliography.

Marsh (1878: plate VIII in part). The only illustration of Diplodocus material in the paper that named the genus.

Marsh (1878: plate VIII in part). The only illustration of Diplodocus material in the paper that named the genus.

What do we think about this?

I used to do this religiously in my early papers, just because it was the done thing. But then I started to think about it. To my mind, it used to make a certain amount of sense 30 years ago. But surely in 2016, if anyone wants to know about the taxonomic history of Diplodocus, they’re going to go straight to Wikipedia?

I’m also not sure what the value is in providing the minimal taxonomic-authority information rather then, say, morphological information. Anyone who wants to know what Diplodocus is would be much better to go to Hatcher 1901, so wouldn’t we serve readers better if we referred to “Diplodocus (Hatcher 1901)”

Now that I come to think of it, I included “Giving the taxonomic authority after first use of each formal name” in my list of
Idiot things that we we do in our papers out of sheer habit three and a half years ago.

Should I just shrug and do this pointless busywork to satisfy the handling editor? Or should I simply refuse to waste my time adding information that will be of no use to anyone?

References

  • Hatcher, Jonathan B. 1901. Diplodocus (Marsh): its osteology, taxonomy and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63 and plates I-XIII.
  • Marsh, O. C. 1878. Principal characters of American Jurassic dinosaurs, Part I. American Journal of Science, series 3 16:411-416.

 

I’ve been lucky enough to acquire another beautiful specimen. It arrived in a box (though not from Amazon, despite what the box itself might suggest):

2016-03-17 15.45.01

What’s inside?

2016-03-17 15.45.48

Can it be? It is!

2016-03-17 15.46.14

Now I’ve wanted a tortoise for a long time, because they are (Darren will back me up here) the freakiest of all tetrapods. Their scapulae and coracoids have somehow migrated inside their rib-cages (which bear the shell), and their dorsal vertebrae are fused to the shell all along its upper midline. Just ridiculous. Look, this is what I’m talking about. Compare with the much saner approach that armadillos use to having a shell.

Here’s my baby in left anterodorsolateral view:

2016-03-17 15.46.27

And in right posteodorsolateral:

2016-03-17 15.46.39

Can anyone tell me what species I have here?

Here he is (or she?) upside down, in left posteroventolateral view.

2016-03-17 15.46.54

Come to think of it, can anyone tell me the sex of my specimen?

Here he or she is in anterior view, looking very stern.

2016-03-17 15.47.25

The problem is — and I can’t quite believe this never occurred to me until I had a tortoise of my own — how on earth do you deflesh such a creature? I have no idea (and obviously no experience). Any hints?

Folks,

For a forthcoming minor paper, I need a good-quality scan of Hatcher’s 1901 monograph on Diplodocus carnegii — specifically, plate VI, the photographs of the cervicals in posterior view.

Here is the best scan I have of it:

CERIVICAL SERIES POSTERIOR

(Click through for full resolution.)

If anyone has something better, please leave a comment or email me on dino@miketaylor.org.uk

Thanks!

A couple of times now, I’ve pitched in an abstract for a Masters project looking at neck cartilage, hoping someone at Bristol will work on it with me co-supervising, but so far no-one’s bitten. Here’s how I’ve been describing it:

Understanding posture and motion in the necks of sauropods: the crucial role of cartilage in intervertebral joints

The sauropod dinosaurs were an order of magnitude bigger than any other terrestrial animal. Much sauropod research has concentrated on their long necks, which were crucial to their success (e.g. Sander et al. 2010). One approach to understanding neck function tries to determine neutral posture and range of motion by modelling the cervical vertebrae as a mechanical system (e.g. Stevens and Parrish 1999).

The raw material of such studies is fossilised vertebrae, but these are problematic for several reasons. The invariable incompleteness and distortion of sauropod neck fossils causes fundamental difficulties; but even given perfect fossils, the lack of preserved cartilage means that the bones are not shaped or sized as they were in life.

Ignoring cartilage has dramatic consequences for neutral posture, range of motion and even length of necks: pilot studies (Cobley 2011, Taylor 2011) found that intact bird necks are 8–12% longer than articulated sequences of their dry bones, and that figure is as high as 24% for a juvenile giraffe neck. A turkey neck postzygapophysis was 26% longer when cartilage was included than after being stripped down to naked bone.

We do not yet know how much articular cartilage sauropods had in their necks, nor even what kind of intervertebral joints they had: crocodilians have fibrocartilaginous discs like those of mammals, while birds have synovial joints, so the extant phylogenetic bracket is uninformative.

The project will involve dissection and measurement of bird and crocodilian necks, documenting the extent and shape of articular cartilage, identifying osteological correlates of fibrocartilaginous and synovial joints, and applying this data to sauropods to determine the nature of their neck joints and length of their necks, to reconstruct the lost cartilage, and to determine its effect on neutral pose and range of motion.

Following completion, we anticipate publication of the project.

References

Cobley, Matthew J. 2011. The flexibility and musculature of the ostrich neck: implications for the feeding ecology and reconstruction of the Sauropoda (Dinosauria: Saurischia). MSc Thesis, Department of Earth Sciences, University of Bristol. vi+64 pages.

Sander, P. Martin, Andreas Christian, Marcus Clauss, Regina Fechner, Carole T. Gee, Eva-Maria Griebeler, Hanns-Christian Gunga, Jürgen Hummel, Heinrich Mallison, Steven F. Perry, Holger Preuschoft, Oliver W. M. Rauhut, Kristian Remes, Thomas Tütken, Oliver Wings and Ulrich Witzel. 2010. Biology of the sauropod dinosaurs: the evolution of gigantism. Biological Reviews 86:117–155. doi:10.1111/j.1469-185X.2010.00137.x

Stevens, Kent A., and J. Michael Parrish. 1999. Neck Posture and Feeding Habits of Two Jurassic Sauropod Dinosaurs. Science 284:798–800. doi:10.1126/science.284.5415.798

Taylor, Michael P., and Mathew J. Wedel. 2011. Sauropod necks: how much do we really know?. p. 20 in Richard Forrest (ed.), Abstracts of Presentations, 59th Annual Symposium of Vertebrae Palaeontology and Comparative Anatomy, Lyme Regis, Dorset, UK, September 12th–17th 2011. 37 pp. http://www.miketaylor.org.uk/dino/pubs/svpca2011/TaylorWedel2011-what-do-we-really-know.ppt

(Obviously some part of this have since been covered by my and Matt’s first cartilage paper, but plenty has not.)

I now think there are two reasons no-one’s taken up this project: first, because I wrote it as very focussed only on the question of what type of joint was present, whereas there are plenty of related issues to be investigated along the way; and second, because I wrote it as a quest to discover a specific treasure (an osteological correlate), with the implication that if there’s no treasure to be found then the project will have been a failure.

But I do think there is still plenty of important work to be done in this area, and that there’s lots of important information to be got out of comparative dissection of extant critters.

If anyone out there fancies working in this area, I’d be delighted. I’d also be happy to offer whatever advice and help I could.

Update (18 October 2014)

Somehow I’d forgotten, when I wrote this post, that I’d previously written a more detailed post about the discs-in-sauropod-necks problem. If you’re interested in the problem, you should read that.

Recently, I published an old manuscript of mine as a PeerJ Preprint.

I wrote this paper in 2003-4, and it was rejected without review when I submitted it back then. (For, I think, specious reasons, but that’s a whole nother discussion. Forget I mentioned it.)

I haven’t touched the manuscript since then (except to single-space it for submission as a preprint). It’s ten years old. That’s a problem because it’s an analysis of a database of dinosaur diversity, and as everyone knows, the rate of recognising new dinosaurs has gone through the roof. That’s the reason I never made any attempt to update and resubmit it: dinosaur diversity is a fast-moving target, and each time through the submit-reject cycle takes long enough for the data to be outdated.

So much for the history. Now the question: how should I cite this paper? Specifically, what date should I give it? If I cite it as from 2004, it will give the misleading impression that the paper has been available for ten years; but if I cite it as from 2014, it will imply that it’s been worked on at some point in the last ten years. Both approaches seem misleading to me.

At the moment, I am citing it as “Taylor (2014 for 2004)”, which seems to more or less capture what’s meant, but I don’t know whether it’s an established convention. Is there an established convention?

Releated: where in mv publications list should it appear? At present I am sorting it under 2014, since that’s when it came out; but should it be under  2004, when it was written? I guess publication date is the one to go far — after all, it’s not unusual even now for papers to spend a year or more in press, and it’s the later (publication) date that’s cited.

Help me out. How should this be done?

References