I’m just back from SVPCA 2010 (the Symposium of Vertebrate Palaeontology and Comparative Anatomy), and what an amazing meeting it was.  I think it was the best I’ve been to.  That’s partly because I understand more of the talks these days — it’s the first time I’ve ever listened to every single talk, even all the mammal-tooth and fish-skull talks — and I learned something interesting and new from almost every one of them.

But as is so often the case, the best thing about the meeting was, well, meeting.  I met with Matt and Darren for the first time in a year, which is always excellent.  And for the first time, I met horizontal-sauropod-neck advocate Kent Stevens.  Kent was there to present one of two talks on horizontal necks, and UK sauropod jockey John Martin presented the other.  Their talks were part of a block of seven sauropod talks — it would have been eight had Michael Pitman not changed his scheduled sauropod-tail talk to a theropod-tail talk.  Matt and I both made presentations, although Darren wasn’t able to because he didn’t know that he’d be able to come to the meeting until the last moment.

After that block of talks, Matt, Darren and I went off to lunch with Kent and Martin.  Despite the lighthearted attempts of session moderator John Hutchinson to build the session up as a two-way fight, it was all rather peaceful and enjoyable.  After lunch we all went to have our photos taken together in front of the Zoology Museum‘s giraffe skeleton:

Sauropod Neck Posture Working Group, 2010 meeting.  From left to right: Darren Naish, Matt Wedel, John Martin, Mike Taylor, Kent Stevens.

As you can see, we were all very civilised and well behaved.

The Sauropod Neck Posture Working Group carefully considers all points of view in a detached, professional and mature manner.

In all seriousness, it’s no secret that we SV-POW!sketeers are very much advocates of a raised habitual posture, and so that we strongly disagree with Kent and John.  We had a lot of fun talking together, but we didn’t find that they presented any compelling new evidence in their talks.  (You can read the abstracts of their talks, and indeed of mine and Matt’s, in the SVPCA abstracts book.)

The case for horizontal or near-horizontal habitual pose rests on two assumptions.  First, that osteological neutral pose (ONP) was habitually adopted; and second, that we can know what ONP was.  We still feel that both of these assumptions are false.  We can’t know ONP because there is not a single sauropod neck skeleton anywhere in the world consisting of undistorted cervicals — and even if we knew what ONP was, it wouldn’t tell us much about what I am suddenly going to call mechanical neutral pose (MNP)[*], because we don’t know anything about the intervertebral cartilage.  And we know that extant animals do not habitually adopt ONP because we have X-rays that show us how they habitually rest, and we know that they don’t match what you get by articulating bones.

[* either John or Kent made the point that ONP != MNP in his talk.  I think they probably used a different name for MNP, but it eludes me for now.  If anyone can remind me, I will switch to their terminology.]


So, anyway, it was a bit frustrating watching John’s talk, and seeing him show many photographs of live animals and claiming that their necks were in ONP, when we knew perfectly well that they were not — because necks lie.  We fear he may have been tricked by the misleading soft-tissue outlines that mask the postures adopted by the neck skeleton in nearly all tetrapods.  As an example, I give you the hoatzin, which happily was on display at the Zoology Museum as both a stuffed specimen and a skeleton:

Hoatzin (Opisthocomus cristatus), stuffed specimen and skeleton.  Note the extraordinarily long cervical skeleton, almost entirely unreflected in the live animal.

Here’s another photograph from the astounding collection of the Zoology Museum (and some day I really ought to blog about the museum itself).  I took this photograph of the neck of a camel with no specific agenda, but when I looked at it again today, one aspect leapt out at me:

Head and neck of dromedary camel (Camelus dromedarius) UMZC H.14191, in right lateral view, with disarticulated C3/C4 and C4/C5 joints.

Notice how very dramatically the third and fourth cervical central fail to contact, and the fourth and fifth.  How uncomfortable this must be for the poor camel — its neck extended (or “dorsiflexed”) far, far out of ONP, to the point where the vertebrae drastically disarticulate.  And yet we all know perfectly well that habitual pose for camels is much more extended than this, and many of us have seen photos of camels leaning their necks right back so that their heads are upside down, and they can rub the top of their head against their back.  Just imagine what that does to the cervical articulations.

More on this subject another time.  For now, I leave you with more from the Sauropod Neck Posture Working Group summit.

Hey!  That hurt!

In case you haven’t heard, Taylor et al. (2009) recently argued that sauropods naturally held their cervico-dorsal junctions in extension, and their cranio-cervical joints in flexion… at least, when they weren’t foraging, feeding or engaged in other such activities [if you need help with those terms please see the Tet Zoo article here].

neck-posture_montage

Given that we here at SV-POW! are predominantly interested in sauropods, and given that the amazing necks of these animals have long been such a source of debate, it stands to reason that sauropods might get used as the ‘poster children’ or exemplars for any particular argument about neck pose in fossil tetrapods. However, as we’ve said here and there – I certainly mentioned it in my Tet Zoo article on the subject – the contention (that cervico-dorsal junctions are maintained in extension, and that cranio-cervical joints are maintained in flexion) holds true for all terrestrial amniotes and, to a degree, all crown-group tetrapods. In this article we’re going to do something a little odd for SV-POW! – we’re going to look at other fossil amniotes to see if and how this affects them. Have any of them also been reconstructed in poses that are not compliant with the data from living animals?

The short answer is yes, yes they have.

First off, fossil mammals mostly get by ok, which is what you’d expect given that they are generally very similar to their extant relatives. Likewise, there aren’t any fossil birds that have been reconstructed incorrectly, and again you’d hope not given that they’re generally highly similar to extant forms. The extinct moa from New Zealand (that’s moa in the plural sense) are sometimes shown standing at rest with non-extended cervico-dorsal junctions, but with extremely strong extension in the anterior part of the neck that makes up for this (Worthy & Holdaway 2002). While extension at the cervico-dorsal junction may be subtle or absent in living ratites when they are feeding or foraging, in relaxed individuals extension at the neck base is indeed present.

Stegosaurs really need a makeover

What about other dinosaurs? Here’s where we do find quite a few reconstructions that contradict our contention. For a start, basal sauropodomorphs – the animals conventionally lumped together as prosauropods – have often been shown with non-extended cervico-dorsal junctions and fully extended cranio-cervical junctions: that is, with necks that emerge in a straight line from the body, and heads that have their long axis parallel to that of the neck. Classic examples include Kermack’s reconstruction of the animal formerly known as Thecodontosaurus and Weishampel & Westphal’s Plateosaurus. There are many others.

Historically, non-avian theropods have been depicted with elevated necks, flexed cranio-cervical junctions and all that. So far so good. One specific exception does come to mind however: Tarsitano (1983) produced a truly awful theropod reconstruction in which the neck was shown as straight and with a non-extended cervico-dorsal junction. The latter is a no-no, and so is straightening the neck this much, as the shapes of the centra and neural arches show that the cervical vertebrae of theropods were held elevated and in a gentle S-curve (see Molnar & Farlow 1990). A few artistic reconstructions of non-avian theropods have given them non-elevated necks (Neave Parker’s megalosaur picture from the 1970s comes to mind), and if you look at the allosaurs that featured in Walking With Dinosaurs you’ll note that their cranio-cervical junctions are extended, not flexed as they should be.

Tarsitano_1983_theropod_posture

Theropod posture as reconstructed by Tarsitano (1983). Tarsitano mostly argued that non-avian theropods were more like crocodilians than birds in musculature and some aspects of posture.

On to ornithischians. It was difficult to keep a tight lip back in February 2009 when the long-necked stegosaur Miragaia longicollum was published. Like the WWD diplodocoids, Miragaia was given a non-extended cervico-dorsal junction and extended cranio-cervical junction: in other words, its neck and head were illustrated projecting forwards in a straight line, as a continuation of the animal’s dorsal column (Mateus et al. 2009). Based on what we know about living animals, it’s more likely that the cervico-dorsal junction was extended, and that the cranio-cervical junction was flexed: in other words, that the neck was strongly elevated relative to the dorsal vertebrae, and that the head was held at an angle to the neck. Given the remarkable length of its neck, this at least makes it possible that Miragaia was a high-browser. I look forward to seeing artistic reconstructions that show this animal with its head held up above its back, rather than extending forwards and parallel to it (actually, I’ve already seen two, but you know what I mean).

In fact, like sauropods, stegosaurs have been flat out abused by palaeontologists, with non-extended cervico-dorsal junctions and fully extended cranio-cervical junctions being the norm across more than 100 years of description and reconstruction. And don’t use the excuse that these reconstructions are all meant to show the animals engaged in feeding or foraging: they’re not. Many of them clearly depict the animals standing, in relaxed poses, and doing nothing. Marsh started it in 1891: he showed the skull of Stegosaurus armatus (then S. stenops) fully extended, rather than flexed, on the neck, and showed the neck continuing in (approximately) a straight line from the dorsals. This reconstruction was hugely influential, of course, and even today the popular conception of the stegosaur – with its horrible over-arched back and down-sloping tail – is based on Marsh’s drawing. Later stegosaur reconstructions by Lull and Gilmore perpetuated the idea of non-extended cervico-dorsal junctions and fully extended cranio-cervical junctions in Stegosaurus (see Czerkas 1987 for a review of stegosaur life reconstructions), and the same posture was later reconstructed for Huayangosaurus, Kentrosaurus, Tuojiangosaurus and others (see Galton & Upchurch 2004).

Tuojiangosaurus_skeleton_NHM

Tuojiangosaurus, as displayed in the Natural History Museum, London. (c) NHM (image from wikipedia). Note the lack of extension at the cervico-dorsal junction and the slight hyper-extension at the cranio-cervical junction.

Those stegosaur reconstructions you can see in some museums – some of which show the cranio-cervical junction in slight hyper-extension (look at the Tuojiangosaurus shown here) – are flat-out horrible and totally contradict the data we have from neck and head posture in extant amniotes (Taylor et al. 2009). In recent decades, reconstructions by artists like Stephan Czerkas and Greg Paul have given stegosaurs raised necks where the cervico-dorsal junction is extended in proper fashion (as per the data from living amniotes). I get the impression, however, that such reconstructions have not been taken seriously by ‘mainstream’ palaeontologists, at least some of whom still seem to think that stegosaurs walked around with their heads two inches off the ground.

Similar mistakes have been made with ankylosaurs: most classic reconstructions show non-extended cervico-dorsal junctions where the neck emerges in a straight line or even slopes downwards, and cranio-cervical junctions that are in full extension. This goes for Ken Carpenter’s Euoplocephalus [shown in composite above] and Sauropelta, Richard Lull’s Nodosaurus, and others (Lull 1921, Carpenter 1982, 1984). Again, the reconstructions that show these neck and head postures do not definitely show the animals in feeding, foraging or searching postures: they are meant to depict the ‘normal’ (viz, relaxed) pose for the animal. A gently elevated neck with an extended cervico-dorsal junction and a flexed cranio-cervical junction is, again, what we should expect given what living animals do, and this has been correctly portrayed by some.

Other ornithischians have generally been reconstructed accurately (at least as goes neck and head posture), but there are, however, a few ceratopsian reconstructions showing non-extended cervico-dorsal junctions and fully extended cranio-cervical junctions. Granger & Gregory (1923) reconstructed Protoceratops in this manner, for example, and ceratopsids have sometimes been shown this way too (Lull 1933). Again, the reconstructions I’m referring to are meant to show normal, relaxed poses, rather than feeding or foraging poses, so criticism is justified. Putting extension into the ceratopsian cervico-dorsal junction raises the head somewhat, such that the top of the frill is now higher than the top of the back rather than lower than it. Notably, some articulated skeletons are displayed this way: the Centrosaurus panel-mount AMNH 5351, shown here, is one of the best examples. Lull thought that the neck had been elevated too much and that the neck posture ‘is that of death rather than that of life’! Peter Galton’s Hypsilophodon (which has mostly been superseded by Greg Paul’s reconstruction these days anyway) should also be considered suspect in view of the strongly extended cranio-cervical junction (Galton 1971, 1974), but the animal was clearly meant to be running at speed, so you could argue that it was shown holding its head and neck in a decidedly un-relaxed pose.

AMNH_Centrosaurus_oblique_June-2009

The excellent Centrosaurus specimen AMNH 5351. Photo borrowed from Traumador the Tyrannosaur. Thanks, Traumador :)

I should point out again at this point that our contention (that cervico-dorsal junctions should be shown in extension in a relaxed animal, and cranio-cervical junctions should be shown in flexion in a relaxed animal) is a hypothesis. It’s possible (unlikely perhaps, but possible) that some stegosaurs, or ankylosaurs, or therapsids, or whatever, did some funky stuff with their occipital condyles or vertebrae and evolved a relaxed head and neck posture different from that of living amniotes, and indeed (as we’ll see in a moment) there surely are at least some exceptions within Amniota. However, if you think a given animal represents a special case, you’re gonna have to demonstrate it.

Shock horror, marine reptiles on SV-POW!

Elsewhere among Reptilia, the data from living lizards and crocodilians indicates that, generally speaking, we should expect fossil forms to hold their necks elevated at moderate angles of between 20-40° relative to the dorsal column when in normal, relaxed pose. Many fossil, non-dinosaurian archosaurs (like rauisuchians and aetosaurs) have been reconstructed this way (mostly because people have looked at living crocodilians when reconstructing these animals), as have fossil squamates and many others.

large_Nicholson_plesiosaur_June-2009

A very old reconstruction of the Jurassic plesiosaur Plesiosaurus.

We do, however, have a contradiction of sorts when we come to sauropterygians (the plesiosaurs and their relatives). Reconstructions of plesiosaurs have evolved in similar fashion to those depicting sauropods: some old reconstructions (some, not all) depict them with extended cervico-dorsal junctions and flexed cranio-cervical junctions (such reconstructions typically show the animals sticking their necks well up out of the water and peering around) (e.g., Williston 1914), but many others show them with non-extended cervico-dorsal junctions and fully extended cranio-cervical junctions. In other words, with the neck and head continuing in a straight line from the dorsal column.

Denver_elasmosaur_June-2009

The elasmosaurid Thalassomedon haningtoni, as displayed at the Denver Museum of Nature and Science. Check out the big neural spines.

Contradicting the idea that plesiosaurs looked down on their prey from above is the fact that their orbits often face slightly or strongly upwards, and there are also indications from their narial and ear anatomy that they were specialised for detecting sensory cues in water, not in air (Cruickshank et al. 1991, Storrs & Taylor 1996). Furthermore, their high-density, often pachyostotic skeletons indicate that they were negatively buoyant animals that were trying their hardest to stay submerged and beneath the surface. All of this indicates that plesiosaurs were subaqueous predators that mostly kept their necks and heads beneath the surface of the water (except when breathing). This makes it very unlikely that their necks were elevated, and indeed – in strong contrast to sauropods and other dinosaurs – there are indications from their vertebral anatomy that neck elevation was not possible in the group (in elasmosaurs, for example, the neural spines on both the cervicals and dorsals are tall and sub-rectangular and it’s difficult to imagine how this would have allowed anything more than extremely subtle extension at the cervico-dorsal junction). So I am going to go out on a limb here (or, more accurately, I’m going to agree with everyone who works on plesiosaurs) and say that plesiosaurs did not hold their necks in the same manner as the extant amniotes that we looked at (Taylor et al. 2009). Is this because they were aquatic, and hence not under the same gravitational constraints as terrestrial amniotes? That looks likely, but we really need to thrash this out once and for all: further work on this is obviously needed, and perhaps it will appear soon. I know from many discussions that plesiosaur researchers talk as much about long necks as sauropod researchers do.

Finally – dicynodonts and other synapsids

Moving now well away from dinosaurs and archosaurs and even reptiles, I’ve had non-mammalian synapsids on my mind an awful lot during all of this. While many of them have relatively short necks, members of some groups have still been shown in downright unlikely postures. Dinocephalians have consistently been shown (correctly) with extended cervico-dorsal junctions and flexed cranio-cervical junctions, so those reconstructions of such things as Titanophoneus and Moschops with their necks held high and their heads at an angle are correct based on the data from living amniotes. However, some reconstructions of some caseids (Stovall’s Cotylorhynchus), dicynodonts (I’m looking at you, Watson’s rendition of Lystrosaurus [shown at top of composite image used above] and Cluver’s Cistecephalus) and gorgonopsids (Colbert’s Lycaenops, for example; shown below) have the cranio-cervical junction in extended or even hyper-extended pose, which again is a total no-no unless there is evidence to the contrary. While some of these animals have been reconstructed in walking or running poses (and hence might be holding their necks and heads in special searching or foraging poses), plenty of others are shown standing on all fours, in relaxed, ‘normal’ poses, so their unusual neck and head poses are, we can assume, meant to be the relaxed, ‘normal’ poses (further examples include King’s Dicynodon and Dinodontosaurus).

Lycaenops_ornatus_AMNM_June-2009

The relatively short necks of these animals mean that, even with the cervico-dorsal junction in full extension, the neck is only elevated by a slight and thoroughly believable 20-40° relative to the dorsal column. Similarly, showing the cranio-cervical junction in flexion is no big deal, as all it does is rotate the skull such that its long axis is at an angle to the neck, rather than acting as a straight-line continuation of it. It seems that more extreme cervico-dorsal extension and cranio-cervical flexion evolved within Mammalia, and hence that non-mammalian synapsids were more like other ‘average’ amniotes in head and neck posture. Nevertheless – again – reconstructions that show the neck and head as straight-line extensions of the back should be considered inconsistent with what we know of neck and neck posture in living amniotes.

Final thoughts

We really hope that our paper will inspire some much-needed debate, and instigate some new work. As you’ll know if you’ve been following the comments on blogs and such, and the media coverage we’ve been getting, there’s every indication that this is exactly what will happen. But what makes this work of particular interest to people in general – and not just to specialists who spend their time worrying about cervical rib morphology and its correlation with functional morphology, or whether the bifurcate neural spines of some sauropods are homologous with the single neural spines of others, and so on – is that it has a real and obvious effect on the life appearance of a fossil animal. And, as I’ve tried to show here, our hypothesis extends beyond the limits of Sauropoda. Stegosaurs and dicynodonts need never look the same way again.

References

  • Carpenter, K. 1982. Skeletal and dermal armor reconstruction of Euoplocephalus tutus (Ornithischia: Ankylosauridae) from the Late Cretaceous Oldman Formation of Alberta. Canadian Journal of Earth Sciences 19, 689-697.
  • Carpenter, K. 1984. Skeletal reconstruction and life restoration of Sauropelta (Ankylosauria: Nodosauridae) from the Cretaceous of North America. Canadian Journal of Earth Sciences 21, 1491-1498.
  • Cruickshank, A. R. I., Small, P. G. & Taylor, M. A. 1991. Dorsal nostrils and hydrodynamically driven underwater olfaction in plesiosaurs. Nature 352, 62-64.
  • Czerkas, S. A. 1987. A reevaluation of the plate arrangement on Stegosaurus stenops. In Czerkas, S. J. & Olson, E. C. (eds) Dinosaurs Past and Present, Volume II. Natural History Museum of Los Angeles County/University of Washington Press (Seattle and Washington), pp. 82-99.
  • Galton, P. M. 1971. Hypsilophodon, the cursorial non-arboreal dinosaur. Nature 231, 159-161.
  • Galton, P. M. 1974. The ornithischian dinosaur Hypsilophodon from the Wealden of the Isle of Wight. Bulletin of the British Museum (Natural History) 25, 1-152.
  • Galton, P. M. & Upchurch, P. 2004. Stegosauria. In Weishampel, D. B., Dodson, P. & Osmólska, H. (eds) The Dinosauria, Second Edition. University of California Press (Berkeley), pp. 343-362.
  • Granger, W. & Gregory, W. K. 1923. Protoceratops andrewsi, a pre-ceratopsian dinosaur from Mongolia. American Museum Novitates 72, 1-9.
  • Lull, R. S. 1921. The Cretaceous armored dinosaur, Nodosaurus textilis Marsh. American Journal of Science 1, 97-126.
  • Lull, R. S. 1933. A revision of the Ceratopsia or horned dinosaurs. Memoirs of the Peabody Museum of Natural History 3, 1-175.
  • Mateus, O., Maidment, S. C. R. & Christiansen, N. A. 2009. A new long-necked ‘sauropod mimic’ stegosaur and the evolution of the plated dinosaurs. Proceedings of the Royal Society of London, Series B (doi:10.1098/rspb.2008.1909)
  • Molnar, R. E & Farlow, J. O. 1992. Carnosaur paleobiology. In Weishampel, D. B., Dodson, P. & Osmólska, H. (eds) The Dinosauria. University of California Press (Berkeley), pp. 210-224.
  • Storrs, G. W. & Taylor, M. A. 1996. Cranial anatomy of a new plesiosaur genus from the lowermost Lias (Rhaetian/Hettangian) of Street, Somerset, England. Journal of Vertebrate Paleontology 16, 403-420.
  • Tarsitano, S. F. 1983. Stance and gait in theropod dinosaurs. Acta Palaeontologica Polonica 28, 251-264.
  • Taylor, M. P., Wedel, M. J. & Naish, D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54, 213-220.
  • Williston, S. W. 1914. Water Reptiles of the Past and Present. University of Chicago Press, Chicago.
  • Worthy, T. H., Holdaway, R. N. 2002. The Lost World of the Moa. Indiana University Press, Bloomington, Indiana.

Welcome, one and all, to Taylor, Wedel and Naish (2009), Head and neck posture in sauropod dinosaurs inferred from extant animals.  It’s the first published paper by the SV-POW! team working as a team, published in Acta Palaeontologica Polonica, and freely available for download here.

Far, far back in the uncharted depths of history, silly people like Osborn and Mook (1921:pl. 84), Janensch (1950b: pl. 8) and Paul (1988:fig. 1), who didn’t know any better, used to depict sauropods with their necks held strongly elevated.

The classic reconstruction of Brachiosaurus brancai, from Janensch (1950b: plate VIII)

The classic reconstruction of Brachiosaurus brancai, from Janensch (1950b: plate VIII. (For some reason, WordPress doesn't allow italics in these captions, hence the roman-font taxonomic names.)

All that began to change with Martin’s (1987) short paper in the Mesozoic Terrestrial Ecosystems volume, and was then turned upside-down by Stevens and Parrish’s (1999) seminal paper in Science: two and a half pages that transformed the way the world looked at sauropods.

xxx

The subhorizontally mounted neck of the Rutland Cetiosaurus skeleton at the Leicester City Museum, in right posterolateral view.

Median part of the subhorizontally mounted neck of the Rutland Cetiosaurus skeleton at the Leicester City Museum, left lateral view.  Mike Taylor for scale.

The median part of the subhorizontally mounted neck of the Rutland Cetiosaurus skeleton at the Leicester City Museum, in left lateral view. Mike Taylor for scale.

John Martin looked at the cervical vertebrae of the Rutland specimen of Cetiosaurus oxoniensis, and concluded that the joints between them couldn’t be as flexible as people thought.  He reconstructed that animal’s neck in a low, near-horizontal pose, and with a very narrow range of movement that didn’t allow it to raise its head far above shoulder level.  Stevens and Parrish brought more rigour to this approach by modelling the cervical articulations of two sauropods (Diplodocus carnegii and Apatosaurus lousiae) using a computer program of their own devising, DinoMorph.  And as most SV-POW! regulars will probably know, they got results similar to Martin’s, showing neutral positions for both animals that were well below horizontal, and finding restricted ranges of motion.  (“neutral pose” here means that the vertebra are aligned such that the zygapophyses overlap as much as possible.)

Diplodocus carnegii, DinoMorph computer model , showing neutral neck posture, and limits of flexibility.  From Stevens (2002:fig. 6a).  [Note that Stevens's more recent models show a slightly higher neck due to its leaving the torso at a less steep angle.]

Diplodocus carnegii, DinoMorph computer model , showing neutral neck posture, and limits of dorsal and ventral flexibility. From Stevens (2002:fig. 6a). (Note that Stevens's more recent models show a slightly higher neck due to its leaving the torso at a less steep angle.)

The DinoMorph posture was quickly adopted as orthodox, and got a lot of exposure in the BBC’s classic CGIumentary, Walking With Dinosaurs: episode 2, Time of the Titans, was primarily about Diplodocus, and under Stevens’s consultancy showed them as having obligate low posture throughout the show.

A still from the BBC Walking With Dinosaurs, episode 2, Time of the Titans, showing Diplodocus in a DinoMorph-compliant posture with a low, horizontal neck.  Image copyright the BBC.

A still from Walking With Dinosaurs, episode 2, Time of the Titans, showing Diplodocus in a DinoMorph-compliant posture with a low, horizontal neck. Image copyright the BBC.

The new horizontal-neck orthodoxy was also reinforced by an exhibition at the American Museum of Natural History featuring a physical metal sculpture of a DinoMorph model:

Physical DinoMorph model at the AMNH, with horizontal-neck advocate Kent Stevens.  Photograph by Rick Edwards, AMNH

Physical DinoMorph model at the AMNH, with horizontal-neck advocate Kent Stevens. Photograph by Rick Edwards, AMNH

This brings us pretty much up to date: there’s been very little in the way of published dissent between 1999 and now, and a couple more Stevens and Parrish papers have reinforced their contention.  Upchurch (2000) published a half-page response to the DinoMorph paper, and Andreas Christian has put out a sequence of papers arguing for an erect neck posture in Brachiosaurus brancai on the basis that this best equalises stress along the intervertebral joints (e.g. Christian and Dzemski 2007), but otherwise all dissent from the DinoMorph posture has been limited to unpublished venues: for example, Greg Paul has posted several messages on the Dinosaur Mailing List disputing the low-necked posture, but has yet to put any of his arguments in print.

But enough of this dinosaury stuff.  Let’s look at a nice, cuddly bunny:

wild-rabbit-41946-480px

Now here’s the thing: you wouldn’t guess by looking at it, but that rabbit has a vertical neck.  In fact, it’s more than vertical: it’s so upright that it bends back on itself.  Don’t believe me?  Then take a look at this X-ray of an unrestrained awake rabbit:

Unrestrained awake rabbit, left lateral view, in X-ray, showing vertical neck. From Vidal et al. (1986:fig. 4B)

Unrestrained awake rabbit, left lateral view, in X-ray, showing vertical neck. From Vidal et al. (1986:fig. 4B)

Amazing.

Can it be that rabbits have unusual cervical vertebrae, such that when you articulate them in neutral pose they curve strongly upwards?  No: and to prove it, here is (ahem) Taylor, Wedel and Naish (2009: fig. 1):

Taylor et al. (2009: fig. 1), reverse for easy comparison with the previous two images: skull and cervical skeleton of the Cape hare (Lepus capensis) in neutral pose and in maximal extension

Taylor et al. (2009: fig. 1), reversed for easy comparison with the previous two images: skull and cervical skeleton of the Cape hare (Lepus capensis) in neutral pose and in maximal extension

(Yes, this is a hare rather than a rabbit, but it’s close enough for government work.)  What we found was that it was only possible to get the cervical skeleton anywhere near the habitual life posture by cranking all the proximal cervical joints up as far as they could physically go.  In fact, it seems that some of the joints in the live animal flex more than the dry bones can — presumably due to intervertebral cartilage moving the centra further apart.

And this is fully in accord with the findings of Vidal et al. (1986), who X-rayed a selection of live animals (human, monkey, cat, rabbit, rat, guinea pig, chicken, monitor lizard, frog) and found that the neck is inclined in all but the frog.  Furthermore, in all the mammals and reptiles, they found that:

  • the cervical column is elevated nearly to the vertical during normal functioning;
  • the middle part of the neck is habitually held relatively rigid;
  • the neck is maximally extended at the cervico-dorsal junction and maximally flexed at the cranio-cervical junction; and
  • it is the cranio-cervical and cervico-dorsal junctions that are primarily involved in raising and lowering the head and neck.

(In life, these facts are obscured from view by soft tissue.)

We also looked at unpublished live-alligator X-rays (thanks to Leon Claessens for access to these) and found that even in these ectothermic sprawlers, the neck is habitually elevated above neutral pose.  Published X-rays of turtles and even (slightly) salamanders also showed the same tendency.

So what does this mean for sauropods?  Simply, unless they were different from all extant terrestrial amniotes, they did not habitually hold their necks in neutral position, but raised well above horizontal.  And if they resembled their closest relatives, the birds — and the only other homeothermic and erect-legged group, the mammals — then their necks were strongly inclined.  As in, all the proximal cervicals were habitually cranked into the most erect positions they could attain.  Kind of like this:

Diplodocus carnegii head, neck and anterior torso, right lateral view, articulated in habitual posture as hypothesised by Taylor et al. (2009).  Skull and vertebrae from Hatcher (1901).

Diplodocus carnegii head, neck and anterior torso, right lateral view, articulated in habitual posture as hypothesised by Taylor et al. (2009). Skull and vertebrae from Hatcher (1901).

Which is a looong way form the DinoMorph posture that we were all getting used to but couldn’t learn to love.  What do you know?  Turns out that Osborn and Mook, and Janensch, were right after all.

So that, in a nutshell, is the contention of the first SV-POW! paper: that sauropods held their heads up high.  That’s not to say that they couldn’t bring them lower when they wanted to — of course they could, otherwise they’d have been unable to drink — but we believe the evidence from extant animals says that they spent the bulk of their time with their heads held high.

I leave you with this rather beautiful piece that noted pterosaurophile Mark Witton drew to illustrate our favoured posture.  Enjoy!

Diplodocus herd -- mostly with necks in habitual raised posture, with one individual drinking.  By Mark Witton.

Diplodocus herd -- mostly with necks in habitual raised posture, with one individual drinking. By Mark Witton.

Stay tuned for more on neck posture …

Update

For more cool stuff about the paper, including blog and media coverage and the chance to hear Mike on BBC Radio(!), see our page about the paper on the sidebar.

References

  • Christian, A. and Dzemski, G. 2007. Reconstruction of the cervical skeleton posture of Brachiosaurus brancai Janensch, 1914 by an analysis of the intervertebral stress along the neck and a comparison with the results of different approaches. Fossil Record 10: 38-­49.
  • Janensch, W. 1950b. Die Skelettrekonstruktion von Brachiosaurus brancai. Palaeontographica (Supplement 7): 97-­103.
  • Martin, J. 1987. Mobility and feeding of Cetiosaurus (Saurischia, Sauropoda) ­ why the long neck? In: P.J. Currie and E.H. Koster (eds.), Fourth Sympo- sium on Mesozoic Terrestrial Ecosystems, Short Papers, 154­-159. Box- tree Books, Drumheller, Alberta.
  • Osborn, H.F. and Mook, C.C. 1921. Camarasaurus, Amphicoelias, and other sauropods of Cope. Memoirs of the American Museum of Natural History, new series 3: 246­-387.
  • Paul, G.S. 1988. The brachiosaur giants of the Morrison and Tendaguru with a description of a new subgenus, Giraffatitan, and a comparison of the world’s largest dinosaurs. Hunteria 2 (3): 1­-14.
  • Stevens, K.A. and Parrish, J.M. 1999. Neck posture and feeding habits of two Jurassic sauropod dinosaurs. Science 284: 798­-800. [Free subscription required]
  • Taylor, M.P., Wedel, M.J. and Naish, D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54(2): 213-220.
  • Upchurch, P. 2000. Neck posture of sauropod dinosaurs. Science 287: 547b.
  • Vidal, P.P., Graf, W., and Berthoz, A. 1986. The orientation of the cervical vertebral column in unrestrained awake animals. Experimental Brain Research 61: 549­-559.

Citation and link to the paper

Woodruff, D. Cary, Wolff, Ewan D.S., Wedel, Mathew J., Dennison, Sophie, and Witmer, Lawrence M. 2022. The first occurrence of an avian-style respiratory infection in a non-avian dinosaur. Scientific Reports 12, 1954. https://doi.org/10.1038/s41598-022-05761-3

YouTube video

SV-POW! posts

Media coverage

I’ll probably give up on tracking all of this myself sooner than I have in the past, given that Altmetric will track most of it for me. Here’s the Altmetric page for this paper (link).

Web

Video

Last time, we looked briefly at my new paper Almost all known sauropod necks are incomplete and distorted (Taylor 2022). As hinted at in that post, this paper had a difficult and protracted genesis. I thought it might be interesting to watch the story of a published paper through its various stages of prehistory and history. Strap in, this is a long one — but hopefully of interest, especially to people who are just coming into academia and wonder how this stuff works in practice.

Taylor (2022: Figure 9). Sequences of cervical vertebrae of extant animals, showing that articular facet shape remains similar along the column. Top. Cervical vertebrae 3–7 of a mature savannah monitor lizard, Varanus exanthematicus, in anterior view. (The cervicals of monitor lizards, unlike those of sauropods and most mammals, are procoelous, with the anterior facet being concave and the posterior convex.) Bottom. cervical vertebrae 2–5 of a mature house-cat, Felis catus, in posterior view.

It’s never easy to identify when a thing started, but I suppose the first seeds of this paper were sown back in 2004, when Matt was planning a visit to London (to meet me in person for the first time, as it happens) and we were planning out what things we might do during the museum time we had booked. The Rutland cetiosaur was on our itinerary, and I wrote to Matt:

I also wondered about trying to measure the radius of curvature of any well-preserved condyles and cotyles. Are there any established procedures for doing this? (And is the material up to it?)

The answer, of course, is “no”. But that wasn’t apparent until I saw the material. That got me started thinking about all the kinds of mechanical analyses we’d like to do with fossil necks, and about how good we would need the material to be for the results to mean anything.

Those ideas percolated for some years.

May 19, 2011: I wrote How long was the neck of Diplodocus?, in which I considered some of the ways that the neck of the Carnegie Diplodocus is not quite so well established as we tend to assume, and went on to make similar observations about the Humboldt brachiosaur Giraffatitan “S II”.

September 18, 2011: I gave a talk (co-authored with Matt) at the Lyme Regis SVPCA, entitled Sauropod necks: how much do we really know?, the first half of which had grown out of the observations in that initial blog-post. (The second half was about the problems caused by the lack of preserved intervertebral cartilage in fossilised vertebrae, and that half became our 2013 PLOS ONE paper.)

September 20, 2013: I wrote Measuring the elongation of vertebrae, in which I discussed a problem with Elongation Index (EI): that crushing of cotyles makes both their vertical height and horizontal width unreliable to use in ratio with vertebral length.

June 4, 2014: I wrote The Field Museum’s photo-archives tumblr, featuring: airbrushing dorsals. Among other photos, I noted one of presacral 6 (probably D7) of the Brachiosaurus altithorax holotype, showing that before it was “restored” into its present state, it was a mosaic of bone fragments.

October 6, 2015: I submitted to PeerJ a manuscript based on these observations and others. At the same time, I published a preprint of the submitted manuscript, and briefly blogged about it under the title My most depressing paper. I expected that the paper would quickly be published in essentially its submitted form.

In the following days, the preprint and blogpost both quickly attracted many comments pointing out complete or near-complete sauropod necks that I had missed in the manuscript’s catalogue of such necks.

October 27, 2015 (only three weeks later!): I got back three reviews which were the very definition of “tough but fair”. They were written by three researchers whose sauropod work I hugely respect and admire — Paul Barrett, Paul Upchurch and Jeff Wilson — and they graciously acknowledged the strengths of the submission as well as bringing numerous justified criticisms. It’s traditional in acknowledgements sections to say nice things about the reviewers, but really these were everything one could hope for.

(I disagreed with only two of the many critical points made: one by Paul Upchurch, which we will come to later; and Paul Barrett’s recommendation that the illustrations should use only specimens in credentialled museums. For fossils, of course, that’s right. But the paper also contains numerous photos of extant-animal vertebrae from my own collection, and that’s OK — common — even, in the extant-animal literature. A house-cat is a house-cat, and the cervicals of one are not going to be meaningfully different from those of another.)

Because it had taken the journals and the reviewers only three weeks to get detailed, helpful, constructive reviews back to me, I was now in a position to make this paper a big success story: to turn the revisions around quickly, and maybe even get an acceptance within a month of submission. The time was right: the material was still fresh in my mind so soon after the initial submission, so it should have been the work of a few evenings to revise according to the reviewers’ requests and get this thing on the road.

That’s not what happened.

Instead, for reasons I can’t begin to fathom, I became downhearted at the prospect of going back to this manuscript and dealing with all the criticisms. I want to emphasize again that this is not in any way a complaint about the reviews, which were not unduly negative. I just looked at them and felt … weary. So I let it slide for a while.

The problem is, “a while” quickly became multiple months. And by then, the material was no longer fresh in my mind, so that doing the work I should have done half a year earlier would now have been a much bigger job. I would have had to load lots of stuff back into mental RAM before I could even get started. And there was always something more appealing to do. So I left it for a full year.

The problem is, “a year” quickly became multiple years. I have no excuse for this.

And for six years, this unconsummated project has been hanging over me, draining my motivation, whispering to me every time I try to work on something else. It’s been a drag on everything I’ve tried to do in palaeo, all because I didn’t summon the energy to drive a stake through its heart back in 2015.

Learn from my mistake, folks: don’t do this.

When you get the reviews back from a submission, give yourself a week to mourn that the reviewers didn’t recognise the pristine perfection of your initial submission, then get back on the horse and do the work. Just like I didn’t.

Seriously: be better than me. (That’s certainly what I plan to do.)

Anyway …

Early 2021: I finally got my act together, and got started on the big revision. And by this point it was a big revision because not only did I have to handle all those long-postponed reviews, and all the comments on the preprint and the blog-posts from 2015. I also had to handle five more years of developments. The biggest effect this had was that I needed to completely rewrite the woefully inadequate catalogue of complete necks, which in the original preprint listed only six species. The new version lists specimens rather than species, and very many more of them. To make the list as comprehensive as possible this time …

January 27, 2021: I created my initial draft of the new list as a Google Doc, and posted Towards a catalogue of complete sauropods necks asking readers on this blog to offer corrections and additions. They did. That resulted in a lot more work as I chased down details of candidate necks in published sources and sought personal communications about others. As a result …

March 24, 2021: I posted the draft list as The catalogue of complete sauropods necks nears completion. A few more comments came in as a result, but the list was apparently approaching a steady state.

March 27, 2021: Matt dropped me a line breaking down the listed necks across a basic phylogeny of sauropods, and counting the occurrences. I thought this was interesting enough to make up a new illustration, which I posted on the blog as Analysing the distribution of complete sauropod necks and added to the in progress revised manuscript.

May 11, 2021: I was working on finding a way to measure the variation of cotyle aspect ratios along preserved necks, so I could show qualitatively that they vary more in sauropod fossils than in bones of extant amniotes. I came up with a way of calculating this, but wondered if it already existed. In my post Help me, stats people! I asked if anyone knew of it, but it seemed no-one did. (In the end, the resubmitted paper offered two versions of this metric: one additive, the other multiplicative. To the best of my knowledge, these are novel, if simple, contributions.)

June 6, 2021: In one of the original reviews, Paul Upchurch had commented that a further confounding factor in understanding neck lengths is identifying the cervicodorsal junction. I started to put together a new manuscript section on that issue, and posted my initial thoughts as What’s the difference between a cervical and dorsal vertebra?. This post, too, generated some useful feedback that made its way into the version of the section that landed up in the revised paper.

At this point, I had put together much of the new material I needed for the resubmission. So I went back to the revised draft, integrated all the new and modified material, and …

July 12 2021: I submitted the new manuscript. Because it was the best part of six years since the old version had been touched, I asked PeerJ to handle it as a new submission, and invited the handling editor to solicit reviews either from the same people who’d done the first round or from different people, as they saw fit. This time I did not also post a pre-print — I really didn’t need yet more comments coming in at this point, I just needed to get the wretched thing over the line.

September 3 2021: the editorial decision was in, based on three reviews: major revisions. sigh. Again, though, the reviewers’ criticisms were mostly legitimate, and I could sympathise with the editor’s decision. One of the reviewers of the new version — Paul Upchurch — had previously reviewed to 2015 version, but the other two were new.

Needless to say, more work was required in response to these new reviews, but it was much more tractable than the big revision had been. I added a brief discussion of retrodeformation. I wrote about how we can use phylogenetic bracketing to estimate cervical counts, and three reasons why this doesn’t work as well as we’d like. I discussed how explicit documentation of articulation and damage mitigates their misleading effects. I removed a sideswipe at the journal Science, which I have to admit was out of place. I added a discussion of different definitions of the elongation index. I clarified the prose to make it clearer that my goal was not to criticise how others had done things, but to lay out for new researchers what pitfalls they will have to deal with.

But the most fundamental issue that arose in this round of review was whether the paper should be published at all. I will quote from Paul Upchurch’s review (since it is freely available, along with all the other reviews and my responses):

I have [a] fundamental, and I fear fatal, [problem] with this paper. First, and most importantly, I think it attempts to address a problem that does not really exist. It sets up a strawman with regard to the need to tell researchers that sauropod necks are less complete than we previously thought. However, I would argue that we are well aware of these issues and that the current paper does not provide convincing evidence that there is a problem with the way we are doing things now. To be clear, I am not saying that the incompleteness of sauropod necks is not a problem – it definitely is. What I’m saying is that there is little value in a paper whose main message is to tell us what we already know and take into account.

(Let me emphasize again that this criticism came in the context of a review that was careful, detailed and in many ways positive. There was absolutely nothing malicious about it — it was just Paul’s honest opinion.)

The interesting thing about this criticism is that there was absolutely nothing I could do to remedy it. A paper criticised for lacking a phylogenetic analysis can be made acceptable to the reviewers by adding a phylogenetic analysis. But a paper criticised for not needing to exist can only stand or fall by the handling editor’s agreement with either the author or the reviewer. So all I could do was write a response in the letter than accompanied my revision:

We now come to Paul’s fundamental issue with this paper: he does not believe it is necessary. He writes “The scientific community working on these issues does not need to be reminded of the general importance of understanding the limitations on the data we use”. Here I suggest he is misled by his own unique perspective as the person who quite possibly knows more about sauropods than anyone else alive. Labouring under “The curse of knowledge”, he charitably assumes other palaeontologists are as well-read and experienced as he is — but almost no-one is. I know that I, for one, desperately needed a paper along these lines when I was new to the field.

Happily, the handling editor agreed with me — as did the other two reviewers, which surely helped: “in a time of ever more sophisticated methods, it is good to be made aware of the general imperfections of the fossil record […] I thus recommend the article for publication”. So:

November 11 2021: I submitted the revised revision, along with the response letter quoted in part above.

December 15 2021: The editor requested some more minor changes. I made some of them and pushed back on a few others, then:

December 20 2021: I submitted a third version of this second attempt at the paper.

December 28 2021 (a welcome belated Christmas present): the paper was finally accepted. From here on, it was just a matter of turning handles.

January 4 2022: The proof PDF arrived, looking lovely but riven with mistakes — some of them my own, having survived multiple rounds of revision; others introduced by the typesetting process, including some unwelcome “corrections” that created new errors.

January 13 2022: I sent back a list of 56 errors that needed correcting.

January 24 2022: The paper was published at PeerJ!

Being of a pedantic turn of mind, I went through the final typeset version to check that all the proofing errors had been fixed. Most had, of course. But one in being fixed had introduced another; another was partially corrected but is still missing an apostrophe in the final version. Small stuff.

And then I went through the “things to do when a paper comes out” checklist: posting an SV-POW! article that I had prepared in the days leading up to publication; updating the SV-POW! sidebar page for this paper; adding the new paper to my publications list (and removing the separate entry for the 2015 preprint); adding it to my univeristy’s IR; adding it to my ORCiD page (though if you omit this, it seems to figure it out on its own after a while — kudos!); and skipping LinkedIn, Mendeley, ResearchGate, Academia.edu and Facebook, none of which I do.

And with that, the quest really is at an end, barring this post and any others that might occur to me to write (I have nothing more planned at this point).

Now it’s time to get that vertebral orientation paper revised and resubmitted!

References

Back in 2017, I showed the world 83.33% of my collection of sauropod-themed mugs. Time passes, and I have lost some of them and gained some more. The tally now stands at eight, and here they are:

My missing Brontomerus mug never did turn up. In the mean time, I have also lost or maybe broken the Sauroposeidon mug, the old black-and-white Archbishop mug, and the single-view Xenoposeidon mug. The dissertation mug still survives, but has faded into total illegibility, so I don’t count it any more.

On the more positive side, the sexual selection mug — second from the right in the old photo, and bottom left in the new one — survives, in fact the only one to have done so. All the others are new acquisitions. Let’s take a look:

Back row, left to right:

  1. The new, improved Archbishop dorsals A and B mug. Unlike the original, this is in glorious colour, and rearranges the elements to show anterior view on the front, and left and right lateral on the sides.
  2. The new, improved Xenoposeidon mug. It’s laid out the same way with the anterior view on the front and left and right lateral views on the sides.
  3. One that Fiona made for my birthday, showing one of the publicity photos from the original Xenoposeidon description: the one of which a newspaper columnist wrote “I wish my husband looked at me the way he looks at this bone”.
  4. A mug made by Mark Witton, which I saw at TetZooCon 2019 and made him an offer for. It shows his own Diplodocus artwork, an update of an earlier piece that he did for Matt, Darren and me to publicise our 2009 paper on sauropod neck posture. (Details here.)

Front row, left to right:

  1. The sole survivor, showing the introductory here’s-what-sauropod-necks-are-like illustration from our 2011 paper on why those necks were not sexually selected.
  2. The sauropod neck gallery used as Figure 3 in my and Matt’s 2013 PeerJ paper “why giraffes have short necks”.
  3. One of the world’s few caudal pneumaticity mugs, using all the illustrations from Matt’s and my 2013 paper, and inspired by the freakily consistent colour palette of those illustrations.
  4. This one needs a bit of explaining. See below.

For reasons that no-one — least of all he — understands, my youngest son bought a pair of Dawn French mugs as a birthday or Christmas present for Fiona. (No-one in our family is particularly a fan, it was one of those random things.) Since then, he has given her five or six more identical mugs.

Because I do not like these, I insist that they hang on one mug tree, and the sauropod mugs on another. It was to break down this mug apartheid that our eldest made for us this final mug, which shows both Dawn French and a reconstruction of the Xenoposeidon vertebra (from my 2018 paper). Where does it live? Usually, it sits on the shelf between the two mug trees.

So this is how things stand. (I drink a lot of tea, so these mugs all see plenty of action.) I really should make myself a new Brontomerus mug, and perhaps a pneumatic variation one.

On 22nd December 2020, I gave this talk (via Zoom) to Martin Sander’s palaeontology research group at the University of Bonn, Germany. And now I am giving it to you, dear reader, the greatest Christmas present anyone could ever wish for:

It’s based on a 2013 paper written with Matt Wedel, which itself goes back through many years slow gestation, originating in a discussion on a car journey in 2008. I must tell the full story some time; but not this time.

In this talk, I start by showing in a hopefully vivid way how very much longer sauropods’ necks were than those of any other animal. Then I explain six of the features that made those very long necks possible: no constraint on vertebral count; small, light heads that did not process food; absolutely large bodies with a quadrepedal bauplan; an avian-style respiratory system; air-filled cervical vertebrae; and elongated neck ribs.

If you want to know more, see that Wedel and Taylor (2013) paper!

Finally, my thanks to René Dederichs, a Student of Paleontology in Martin Sander’s work group at the University of Bonn. He organized this event, and recorded the talk for me.

References

 

Daniel Vidal et al.’s new paper in Scientific Reports (Vidal et al. 2020) has been out for a couple of days now. Dealing as it does with sauropod neck posture, it’s obviously of interest to me, and to Matt. (See our earlier relevant papers Taylor et al. 2009, Taylor and Wedel 2013 and Taylor 2014.)

Overview

To brutally over-summarise Vidal et al.’s paper, it comes down to this: they digitized the beautifully preserved and nearly complete skeleton of Spinophorosaurus, and digitally articulated the scans of the bones to make a virtual skeletal mount. In doing this, they were careful to consider the neutral pose of consecutive vertebrae in isolation, looking at only one pair at a time, so as to avoid any unconscious biases as to how the articulated column “should” look.

Then they took the resulting pose, objectively arrived at — shown above in their figure 1 — and looked to see what it told them. And as you can well see, it showed a dramatically different pose from that of the original reconstruction.

Original skeletal reconstruction of Spinophorosaurus nigerensis (Remes et al. 2009:figure 5, reversed for ease of comparison). Dimensions are based on GCP-CV-4229/NMB-1699-R, elements that are not represented are shaded. Scale bar = 1 m.

In particular, they found that as the sacrum is distinctly “wedged” (i.e. its anteroposterior length is greater ventrally than it is dorsally, giving it a functionally trapezoidal shape, shown in their figure 1A), so that the column of the torso is inclined 20 degrees dorsally relative to that of the tail. They also found lesser but still significant wedging in the last two dorsal vertebrae (figure 1B) and apparently some slight wedging in the first dorsal (figure 1C) and last cervical (figure 1D).

The upshot of all this is that their new reconstruction of Spinophorosaurus has a strongly inclined dorsal column, and consequently a strongly inclined cervical column in neutral pose.

Vidal et al. also note that all eusauropods have wedged sacra to a greater or lesser extent, and conclude that to varying degrees all eusauropods had a more inclined torso and neck than we have been used to reconstructing them with.

Response

I have to be careful about this paper, because its results flatter my preconceptions. I have always been a raised-neck advocate, and there is a temptation to leap onto any paper that reaches the same conclusion and see it as corroboration of my position.

The first thing to say is that the core observation is absolutely right, — and it’s one of those things that once it’s pointed out it’s so obvious that you wonder why you never made anything of it yourself. Yes, it’s true that sauropod sacra are wedged. It’s often difficult to see in lateral view because the ilia are usually fused to the sacral ribs, but when you see them in three dimensions it’s obvious. Occasionally you find a sacrum without its ilium, and then the wedging can hardly be missed … yet somehow, we’ve all been missing its implications for a century and a half.

Sacrum of Diplodocus AMNH 516 in left lateral and (for our purposes irrelevant) ventral views. (Osborn 1904 figure 3)

Of course this means that, other thing being equal, the tail and torso will not be parallel with each other, but will project in such a way that the angle between them, measured dorsally, is less than 180 degrees. And to be fair, Greg Paul has long been illustrating diplodocids with an upward kink to the tail, and some other palaeoartists have picked up on this — notably Scott Hartman with his very uncomfortable-looking Mamenchisaurus.

But I do have three important caveats that mean I can’t just take the conclusions of the Vidal et al. paper at face value.

1. Intervertebral cartilage

I know that we have rather banged on about this (Taylor and Wedel 2013, Taylor 2014) but it remains true that bones alone can tell us almost nothing about how vertebrae articulated. Unless we incorporate intervertebral cartilage into our models, they can only mislead us. To their credit, Vidal et al. are aware of this — though you wouldn’t know it from the actual paper, whose single mention of cartilage is in respect of a hypothesised cartilaginous suprascapula. But buried away the supplementary information is this rather despairing paragraph:

Cartilaginous Neutral Pose (CNP): the term was coined by Taylor for “the pose found when intervertebral cartilage [that separates the centra of adjacent vertebrae] is included”. Since the amount of inter-vertebral space cannot be certainly known for most fossil vertebrate taxa, true CNP will likely remain unknown for most taxa or always based on estimates.

Now this is true, so far as it goes: it’s usually impossible to know how much cartilage there was, and what shape it took, as only very unusual preservational conditions give us this information. But I don’t think that lets us out from the duty of recognising how crucial that cartilage is. It’s not enough just to say “It’s too hard to measure” and assume it didn’t exist. We need to be saying “Here are the results if we assume zero-thickness cartilage, here’s what we get if we assume cartilage thickness equal to 5% centrum length, and here’s what we get if we assume 10%”.

I really don’t think it’s good enough in 2020 to say “We know there was some intervertebral cartilage, but since we don’t know exactly how much we’re going to assume there was none at all”.

The thing about incorporating cartilage into articulating models is that we would, quite possibly, get crazy results. I refer you to the disturbing figure 4 in my 2014 paper:

Figure 4. Effect of adding cartilage to the neutral pose of the neck of Diplodocus carnegii CM 84. Images of vertebra from Hatcher (1901:plate III). At the bottom, the vertebrae are composed in a horizontal posture. Superimposed, the same vertebrae are shown inclined by the additional extension angles indicated in Table 2.

I imagine that taking cartilage into account for the Spinophorosaurus reconstruction might have given rise to equally crazy “neutral” postures. I can see why Vidal et al. might have been reluctant to open that can of worms; but the thing is, it’s a can that really needs opening.

2. Sacrum orientation

As Vidal et al.’s figure 1A clearly shows, the sacrum of Spinophorosaurus is indeed wedge-shaped, with the anterior articular surface of the first sacral forming an angle of 20 degrees relative to the posterior articular surface of the last:

But I don’t see why it follows that “the coalesced sacrum is situated so that the posterior face of the last sacral centrum is sub-vertical. This makes the presacral series slope dorsally and allows the tail to be subhorizontal (Figs. 1 and 4S)”. Vidal et al. justify this by saying:

Since a subhorizontal tail has been known to be present in the majority of known sauropods[27, 28, 29], the [osteologically induced curvature] of the tail of Spinophorosaurus is therefore compatible with this condition.

But those three numbered references are to Gilmore 1932, Coombs 1975 and Bakker 1968 — three venerable papers, all over fifty years old, dating from a period long before the current understanding of sauropod posture. What’s more, each of those three was about disproving the previously widespread assumption of tail-dragging in sauropods, but the wedged sacrum of Spinophorosaurus if anything suggests the opposite posture.

So my question is, given that the dorsal and caudal portions of the vertebral column are at some specific angle to each other, how do we decide which (if either) is horizontal, and which is inclined?

Three interpretations of the wedged sacrum of Spinophorosaurus, in right lateral view. In all three, the green line represents the trajectory of the dorsal column in the torso, and the red line that of the caudal column. At the top, the tail is horizontal (as favoured by Vidal et al. 2020) resulting in an inclined torso; at the bottom, the torso is horizontal, resulting in a dorsally inclined tail; in the middle, an intermediate posture shows both the torso and the tail slightly inclined.

I am not convinced that the evidence presented by Vidal et al. persuasively favours any of these possibilities over the others. (They restore the forequarters of Spinophorosaurus with a very vertical and ventrally positioned scapula in order to enable the forefeet to reach the ground; this may be correct or it may not, but it’s by no means certain — especially as the humeri are cross-scaled from a referred specimen and the radius, ulna and manus completely unknown.)

3. Distortion

Finally, we should mention the problem of distortion. This is not really a criticism of the paper, just a warning that sacra as preserved should not be taken as gospel. I have no statistics or even systematic observations to back up this assertion, but the impression I have, from having looked closely at quite a lot of sauropod vertebra, is the sacra are perhaps more prone to distortion than most vertebrae. So, for example, the very extreme almost 30-degree wedging that Vidal et al. observed in the sacrum of the Brachiosaurus altithorax holotype FMNH PR 25107 should perhaps not be taken at face value.

Now what?

Vidal el al. are obviously onto something. Sauropod sacra are screwy, and I’m glad they have drawn attention in a systematic way to something that had only been alluded to in passing previously, and often in a way that made it seems as though the wedging they describe was unique to a few special specimens. So it’s good that this paper is out there.

But we really do need to see it as only a beginning. Some of the things I want to see:

  • Taking cartilage into account. If this results in silly postures, we need to understand why that is the case, not just pretend the problem doesn’t exist.
  • Comparison of sauropod sacra with those of other animals — most important, extant animals whose actual posture we can observe. This might be able to tell us whether wedging really has the implications for posture that we’re assuming.
  • Better justification of the claim that the torso rather than the tail was inclined.
  • An emerging consensus on sauropod shoulder articulation, since this also bears on torso orientation. (I don’t really have a position on this, but I think Matt does.)
  • The digital Spinophorosaurus model used in this study. (The paper says “The digital fossils used to build the virtual skeleton are deposited and accessioned at the Museo Paleontológico de Elche” but there is no link, I can’t easily find them on the website and they really should be published alongside the paper.)

Anyway, this is a good beginning. Onward and upward!

References

  • Bakker, Robert T. 1968. The Superiority of Dinosaurs. Discovery 3:11–22.
  • Coombs, Walter P. 1975. Sauropod habits and habitats. Palaeogeography, Palaeoclimatology, Palaeoecology 17:1-33.
  • Gilmore, Charles W. 1932. On a newly mounted skeleton of Diplodocus in the United States National Museum. Proceedings of the United States National Museum 81:1-21.
  • Hatcher, John Bell. 1901. Diplodocus (Marsh): its osteology, taxonomy, and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63.
  • Osborn, Henry F. 1904. Manus, sacrum and caudals of Sauropoda. Bulletin of the American Museum of Natural History 20:181-190.
  • Taylor, Michael P. 2014. Quantifying the effect of intervertebral cartilage on neutral posture in the necks of sauropod dinosaurs. PeerJ 2:e712. doi:10.7717/peerj.712
  • Taylor, Michael P., and Mathew J. Wedel. 2013c. The effect of intervertebral cartilage on neutral posture and range of motion in the necks of sauropod dinosaurs. PLOS ONE 8(10):e78214. 17 pages. doi:10.1371/journal.pone.0078214
  • Taylor, Michael P., Mathew J. Wedel and Darren Naish. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54(2):213-230.
  • Vidal, Daniel, P Mocho, A. Aberasturi, J. L. Sanz and F. Ortega. 2020. High browsing skeletal adaptations in Spinophorosaurus reveal an evolutionary innovation in sauropod dinosaurs. Scientific Reports 10(6638). Indispensible supplementary information at https://static-content.springer.com/esm/art%3A10.1038%2Fs41598-020-63439-0/MediaObjects/41598_2020_63439_MOESM1_ESM.pdf
    doi:10.1038/s41598-020-63439-0

Here at SV-POW! we’re big fans of the way that animals’ neck skeletons are much more extended, and often much longer, than you would guess by looking at the complete animal, with its misleading envelope of flesh.

Here’s another fine example, from John Hutchinson’s new post A Museum Evolves:

Solitaire (flightless bird), skeleton and taxidermy at University Museum of Zoology at Cambridge (UMZC). Photo by John Hutchinson.

Looking at the stuffed bird, it seems that it could get by perfectly well with half as many cervical vertebra, if only it didn’t carry them in such a strange posture.

Well — I say strange. It seems inefficient, yet it must be doing something useful, because it’s essentially ubiquitous among birds and many mammals … including rabbits, as long-time readers will remember.

This post started out as a comment on this thread, kicked off by Dale McInnes, in which Mike Habib got into a discussion with Mike Taylor about the max size of sauropods. Stand by for some arm-waving. All the photos of outdoor models were taken at Dino-Park Münchehagen back in late 2008.

I think it’s all too easy to confuse how big things do get from how big they could get, assuming different selection pressures and ecological opportunities. I’m sure someone could write a very compelling paper about how elephants are as big as they could possibly be, or Komodo dragons, if we didn’t have indricotheres and Megalania to show that the upper limit is elsewhere. This is basically what Economos (1981) did for indricotheres, either forgetting about sauropods or assuming they were all aquatic.

Truly, a mammal of excellence and distinction. With Mike and some dumb rhino for scale.

In fact, I’ll go further: a lot of pop discussions of sauropod size assume that sauropods got big because of external factors (oxygen levels, etc.) but were ultimately limited by internal factors, like bone and cartilage strength or cardiovascular issues. I think the opposite is more likely: sauropods got big because of a happy, never-repeated confluence of internal factors (the Sander/et al. [2008, 2011, 2013] hypothesis, which I think is extremely robust), and their size was limited by external, ecological factors.

Take a full-size Argentinosaurus or Bruhathkayosaurus – even modest estimates put them at around 10x the mass of the largest contemporary predators. Full-grown adults were probably truly predator-immune, barring disease or senescence. So any resources devoted to pushing the size disparity higher, instead of invested in making more eggs, would basically be wasted.

If there was reproductive competition among the super-giants, could the 100-tonners have been out-reproduced by the 70-tonners, which put those extra 30 tonnes into making babies? Or would the 100-tonners make so many more eggs than the 70-tonners (over some span of years) that they’d still come out on top? I admit, I don’t know enough reproductive biology to answer that. (If you do, speak up in the comments!) But if – if – 70-tonners could out-reproduce 100-tonners, that by itself might have been enough to put a cap on the size of the largest sauropods.

Another possibility is that max-size adult sauropods were neither common nor the target of selection. In most populations most of the time, the largest individuals might have been reproductively active but skeletally-immature and still-growing subadults (keep in mind that category would encompass most mounted sauropod skeletons, including the mounted brachiosaurs in Chicago and Berlin). If such individuals were the primary targets of selection, and they were selected for a balance of reproductive output and growth, then the few max-size adults might represent the relatively rare instances in which the developmental program “overshot” the selection target.

Dave Hone and Andy Farke and I mentioned this briefly in our 2016 paper, and it’s come up here on the blog several times before, but I still have a hard time wrapping my head around what that would mean. Maybe the max-size adults don’t represent the selective optimum, but rather beneficial traits carried to extreme ends by runaway development. It seems at least conceivable that the bodies of such animals might have been heavily loaded with morphological excrescences – like 15- to 17-meter necks – that were well past the selective optimum. As long as those features weren’t inherently fatal, they could possibly have been pretty darned inefficient, riding around on big predator-immune platforms that could walk for hundreds of kilometers and survive on garbage.

What does that swerve into weird-but-by-now-well-trod ground have to do with the limits on sauropod size? This: if max-size adults were not heavy selection targets, either because the focus of selection was on younger, reproductively-active subadults, or because they’d gotten so big that the only selection pressure that could really affect them was a continent-wide famine – or both – then they might not have gotten as big as they could have (i.e., never hit any internally-imposed, anatomical or biomechanical limits) because nothing external was pushing them to get any bigger than they already were.

Or maybe that’s just a big pile of arm-wavy BS. Let’s try tearing it down, and find out. The comment thread is open.

References