Tetrapod Zoology

The world’s most amazing sauropod

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By now you might have heard the thrilling news that Britain has a brand-new sauropod dinosaur: it’s an animal that I’ve obliquely alluded to many times here at Tet Zoo (since February 2006 in fact), and its study and publication have been many months – in fact years – in the making. Yes, it’s (arguably) the world’s most amazing sauropod… Xenoposeidon proneneukos Taylor & Naish, 2007, an enigmatic and morphologically bizarre Lower Cretaceous neosauropod from the Wealden Supergroup rocks of East Sussex, described in the new issue of Palaeontology (Taylor & Naish 2007). At last, readers with good memories will understand why I’ve been making all those veiled references to the inherent coolness of names that start with ‘xeno’. The story behind Xenoposeidon‘s massive awesomeness is a long one, and the implications of its discovery are immense (sort of)…..

Let’s get one thing out of the way to begin with: Xenoposeidon proneneukos is known only from a single bone – a posterior dorsal vertebra – and not a particularly big one at that (it has a preserved height of 30 cm and is about 20 cm long). We’ll get to the ‘naming new taxa on single bones’ issue in a moment, and – yes – I’m being somewhat tongue-in-cheek hyperbolic when I refer to this taxon as ‘the world’s most amazing sauropod’. And, despite the fact that Xenoposeidon is a ‘new’ dinosaur, it most certainly isn’t a recently discovered fossil. Like so many recently named taxa, it’s actually been sitting in a museum collection (that of the Natural History Museum in London) for a loooong time; since the 1890s in fact.

Discovered by Philip James Rufford (best known for the good collection of fossil plants he amassed), it was later sent to the museum and then briefly described by Richard Lydekker. Palaeontologists generally know Lydekker as a prolific describer of Jurassic and Cretaceous fossil reptiles, whereas other zoologists better associate him with taxonomic work on living elephants, lions, deer and dolphins, and on biogeography (it ain’t called Lydekker’s Line for nothin’). Lydekker (1893) provided a very nice figure of the specimen (later given the catalogue number BMNH R2095) and suggested that it might be referable to the Wealden sauropod species that he referred to as Morosaurus brevis (must… avoid… discussion… of… hideous… taxonomic… mess) [the excellent figure from Lydekker (1893) is shown below. BMNH R2095 is on the left; the specimen on the right is an Isle of Wight brachiosaur vertebra]. Opinions on BMNH R2095 were then provided by Harry Seeley, John Hulke and Edwin Newton: all of them distinguished and experienced veterans of British dinosaur research. Furthermore, over the years just about everyone who’s ever worked on sauropods has visited the excellent collection in the NHM and thus might well have seen, or examined, BMNH R2095 (though admittedly only a few of them have spent special time with the Wealden material). But despite all this, there are (so far as we know) no post-Lydekker (1893) comments on BMNH R2095 anywhere in the literature (well, it’s alluded to in Naish & Martill (2007, p. 499), but that doesn’t count).

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Enter Mike P. Taylor, computer programmer by day and sauropod vertebra specialist by night [Mike is shown in the image at the top of the article, posing romantically with BMNH R2095]. Mike is either the best, or worst, sort of palaeontologist: the sort that is essentially devoted to a single, highly arcane, very restricted field of interest… in this case the study of sauropod presacral vertebrae*. Mike’s particularly into brachiosaurs, and as well as studying the taxa from the Morrison Formation and Tendaguru deposits of Tanzania he’s also been looking at the members of this group that come from the Lower Cretaceous Wealden Supergroup of southern England. But not all Wealden sauropods are brachiosaurs – there’s a lot of other stuff there, and among the bits and pieces sat in the NHM collection, Mike stumbled upon, and became intrigued by, the probably non-brachiosaurian BMNH R2095. I’d never looked at R2095 (though given my work on Wealden sauropods (Naish 2005, Naish & Martill 2001, 2007, Naish et al. 2004) maybe I should have), but I did know of it from Lydekker’s description and thought that it looked sort of odd. After Mike and I got corresponding on it we ended up co-authoring a description. The big deal is that BMNH R2095 isn’t just some random vertebra that might have belonged to any old sauropod: it’s a radically new, highly divergent specimen, representing a quite novel suite of anatomical features, and apparently indicating the presence of a hitherto undocumented sauropod lineage.

* Although that’s not entirely accurate, as he’s also published on phylogenetic definitions and on dinosaur diversity patterns over time, and he does sometimes look at limb bones and girdles. His published articles are available here.

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Several features make BMNH R2095 morphologically distinctive: in fact the specimen is unusually well-endowed, if you will, with unique characters (or autapomorphies as they’re properly known) [in adjacent image of BMNH R2095, anterior is to the left]. The neural arch extends for the entire length of the centrum (weird), the neural arch slopes forward relative to the vertebra’s vertical axis (very weird), bony laminae form a sort of vaulted arch over the anterior part of the neural canal (highly weird), and the neural canal itself is asymmetrical, being small and circular posteriorly but tall and tear drop-shaped anteriorly (really weird)… there are other autapomorphies too, mostly involving the arrangement of laminae on the neural arch. If you aren’t familiar with these anatomical terms and need some explanation, the good news is that you now have the awesome guide that is SV-POW! to help you.

These features aren’t seen in any of the other sauropods of the Wealden Supergroup, nor indeed in any other sauropod from anywhere else in the world: accordingly, BMNH R2095 is a diagnosable taxonomic entity, and as such the right thing to do is to name it as a new taxon. We chose the name Xenoposeidon proneneukos (we’re even good enough to provide a pronunciation guide in the paper: ZEE-no-puh-SYE-d’n pro-nen-YOO-koss). Since Matt Wedel and colleagues named the North American brachiosaur Sauroposeidon in 2000 (Wedel et al. 2000), Mike has been flirting with the idea of using ‘poseidon’ as the root of further sauropod names* – Poseidon wasn’t just the god of the sea, he was also in charge of earthquakes, and associating the name with sauropods does seem apt (although it has to be said that it endorses the popular misconception that sauropods made the ground shake every time they walked). ‘Xeno’ means strange or alien (hence xenomorph, Xenopus, Xenosyneunitanura…) and was used to reflect the genuinely weird, unique morphology of BMNH R2095. ‘Proneneukos’ means something like ‘forward sloping’ and of course refers to one of the neural arch’s most distinctive anatomical features.

* We informally refer to MIWG.7306 as ‘Angloposeidon’ [ver 1 articles on it start here]; would it ruin the surprise if I said that other ‘poseidon’ names are in the system?

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With its complex system of bony neural arch laminae, large and invasive pneumatic foramina, and large size, Xenoposeidon is undoubtedly a sauropod dinosaur – there just aren’t any other animals with vertebrae like this [adjacent image shows Xenoposeidon in multiple views. Clockwise from top left: left lateral, right lateral, posterior, anterior]. Furthermore, because the pneumatic foraminae are particularly deep, and the vertebra’s interior consists of multiple large chambers, Xenoposeidon surely belongs to the ‘higher sauropod’ clade called Neosauropoda. Beyond that, however, its affinities are unclear. Xenoposeidon lacks the features that would allow it to be allied with any of the major neosauropod clades (the diplodocoids, camarasaurs, brachiosaurs or titanosaurs) and looks very different from all of them. So it seems to be out there on its own: a neosauropod doing something quite weird, apparently representing a distinct lineage that, if we still used Linnaean ranks in taxonomy, would be given its own Family and Superfamily. While we arrived at this conclusion by way of traditional comparison, we also coded Xenoposeidon for phylogenetic analysis and threw it into a large sauropod data set (the one produced by Harris (2006) in his work on the diplodocoid Suuwassea). The best conclusion that can be drawn from our results is that, again, Xenoposeidon is a neosauropod that can’t be convincingly referred to any of the other major neosauropod clades.

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So we seem to have an entirely new sort of sauropod. That’s pretty cool. The possibility does exist, of course, that Xenoposeidon is in fact a strongly divergent member of one of those long-recognised groups, and it’s also possible that this one specimen is a freak of some sort: a member of a less bizarre taxon that did some weird embryological hocus-pocus when growing its bones, or an individual that was afflicted with some unidentified Cretaceous disease. Both of these hypotheses however are far, far more radical than the conclusion that this is a new taxon representing a new group. It’s also just about possible that Xenoposeidon might turn out to be the same thing as other sauropods known from contemporaneous rocks, like ‘Pelorosaurus’ becklesii. This sauropod, named for forelimb bones and famous for having skin impressions preserved, is a titanosaur (Upchurch 1995, Upchurch et al. 2004, Naish & Martill 2007). Then again, Xenoposeidon doesn’t resemble titanosaur vertebrae in the least, so this is also not a favourable hypothesis.

Of course, there’s always the fact that Xenoposeidon is based on but a single bone. Should we have been so bold as to go as far as naming a new taxon on the basis of such meagre evidence? Here we come to something that experts disagree on. Some workers argue, on principle alone, that the naming of new species on single elements is bad practise. This sounds good and sensible, but – in the case of diagnostic specimens like BMNH R2095 – naming it really is the right thing to do. As one of our reviewers noted, Xenoposeidon is diagnosed by more autapomorphies than are certain other sauropods known from near-complete skeletons! Furthermore, as Naish & Martill (2007) argued, naming taxa – even those based on poor material – is a useful exercise simply because people remember the taxa that get named, but tend to forget or ignore things like ‘new taxon c’ when it comes to tallying diversity. I discussed this subject before in an article on British dinosaurs (here).

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As a specialist on Wealden dinosaurs I find the discovery of a new Wealden sauropod particularly exciting. But what might be missed by many people is that Xenoposeidon is not contemporaneous with all those Isle of Wight dinosaurs that the Wealden is best known for. Contrary to the idea that the Wealden represents one brief span of Lower Cretaceous time inhabited by one assemblage of creatures, the term ‘Wealden’ in fact applies to a unit of rocks (properly called the Wealden Supergroup) that were deposited over about 25 million years, from Berriasian times (right down at the start of the Early Cretaceous) to early Aptian times (close to the ‘middle’ of the Cretaceous). The Wealden Supergroup is divided into three groups: the Hastings Beds Group and Weald Clay Group (both of the Weald sub-basin of the English mainland) and the Wealden Group of the Wessex sub-basin of the Isle of Wight (this might be familiar if you read the Valdoraptor and Becklespinax article) [adjacent image shows what a partial series of Xenoposeidon dorsal vertebrae might look like... sigh, if only we had more].

Based on its locality data and on the origin of the other Wealden fossils collected by Rufford, we think that Xenoposeidon comes from the Ashdown Beds Formation, and this is part of the Hastings Beds Group. Furthermore, the part of the Ashdown Beds Formation exposed at Ecclesbourne Glen (the probable site of origin of Xenoposeidon) is Berriasian in age. So Xenoposeidon is a really, really old Wealden dinosaur – removed by about 20 million years from Isle of Wight Wealden dinosaurs like Eotyrannus and Hypsilophodon. Worth noting here is that the Hastings Beds Group includes a pretty rich and diverse dinosaur assemblage, and that the dinosaurs from Hastings and the surrounding region might now equal or exceed the Isle of Wight in terms of taxonomic diversity. That’s a subject for another time.

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In fact, everything else is now going to be a subject for another time, as this article is too long and I have to stop there. As you’ll know if you’ve visited SV-POW! today, that site will be hosting a whole week of Xenoposeidon-based goodness, so Mike, Matt and I will all have much more to say about it there. You can obtain a pdf of the Taylor & Naish (2007) paper by emailing Mike or myself. Mike has prepared two webpages that provide supplementary information on Xenoposeidon: the Introducing Xenoposeidon page was written for journalists, while the supplementary information page provides other researchers with additional figures, maps and the data used in our cladistic analysis. There is now a reasonable amount of newsy coverage of Xenoposeidon on the web: highlights include Dr Vector’s take on it here [the adjacent image is only half-serious and meant to show the relative position of the Xenoposeidon holotype within its owner. Note that Xenoposeidon was not a particularly big sauropod].

We hope very much that additional specimens of Xenoposeidon might be discovered or recognised in future, now that the whole world knows…

PS – by now, the new news on the African rebbachisaurid Nigersaurus is also out (in PLoS ONE here). This sauropod is known from slightly more complete remains than Xenoposeidon, but would still not be able to beat it in a fight :) And I’d like to say more, but can’t do so right now. As those of you who saw the version of this Xenoposeidon article on Tet Zoo ver 1 will know (it’s now been removed), I’ve been having extreme problems in getting this article published; something to do with cookies apparently. Still, got there in the end.

Refs – –

Harris, J. D. 2006. The significance of Suuwassea emilieae (Dinosauria, Sauropoda) for flagellicaudatan intrarelationships and evolution. Journal of Systematic Palaeontology 4, 185-198.

Lydekker, R. 1893. On a sauropodous dinosaurian vertebra from the Wealden of Hastings. Quarterly Journal of the Geological Society, London 49, 276-280.

Naish, D. 2005. The sauropod dinosaurs of the Wealden succession (Lower Cretaceous) of southern England. The Quarterly Journal of the Dinosaur Society 4 (3), 8-11.

– . & Martill, D. M. 2001. Saurischian dinosaurs 1: Sauropods. In Martill, D. M. & Naish, D. (eds) Dinosaurs of the Isle of Wight. The Palaeontological Association (London), pp. 185-241.

– . & Martill, D. M. 2007. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia. Journal of the Geological Society, London 164, 493-510.

– ., Martill, D. M., Cooper, D. & Stevens, K. A. 2004. Europe’s largest dinosaur? A giant brachiosaurid cervical vertebra from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 25, 787-795.

Taylor, M. P. & Naish, D. 2007. An unusual new neosauropod dinosaur from the Lower Cretaceous Hastings Beds Group of East Sussex, England. Palaeontology 50, 1547-1564.

Upchurch, P. 1995. The evolutionary history of sauropod dinosaurs. Philosophical Transactions of the Royal Society, London 349, 365-390.

Upchurch, P., Barrett, P. M. & Dodson, P. 2004. Sauropoda. In: Weishampel, D. B., Dodson, P. & Osmlska, H. (eds) The Dinosauria, Second Edition. University of California Press, Berkeley, pp. 259-322.

Comments

  1. #1 John H
    November 15, 2007

    I love the silhouette pic with the 1 vertebra in white; I saw that and chuckled before I read the explanatory text. But you shoulda added some giant bat wings or something (in dotted lines of course). :)

    I can see why you didn’t name it Xenusaurus; lawsuits and dinos don’t mix well…

    Seriously though, congrats on the paper!

  2. #2 Adam
    November 15, 2007

    I heard somewhere that some cool sauropod news was coming this week, and this certainly qualifies. That’s definitely a weird one. Are the Hastings Beds prolific enough to hold out hope for anything more, from either Xenoposeidon or the other mysterious critters they have produced?
    Bring on the Poseidon-names!

  3. #3 Mike from Ottawa
    November 15, 2007

    That is weird. Especially the neural canal. I can’t even begin to imagine what’s with that.

    Thanks for posting this.

    I had a look at Mike’s supplementary pics and they are wonderful. Especially the colour ones at the bottom of the page. I don’t know that I’ve ever seen pics of dino bones that look so, well, so much like actual bones. It must be awesome to actually touch something like that.

  4. #4 rajita
    November 15, 2007

    I thought your were to announce Nigersaurus’s ungainly posture. But it looks as though this was much more of a sauropod week.

  5. #5 Michael P. Taylor
    November 16, 2007

    Needless to say, John, the “skeletal reconstruction” was done as a joke. But as we were preparing the publicity for the release of the paper, lots of people seemed to really like it, so I included it on the media-friendly Xeno page, and sure enough it’s been used in more places than any of the other graphics :-) Since it’s now out there and all over the popular press, i ought to say that the silhouette is from Matt Wedel’s Brachiosaurus reconstruction.

    Thanks, Mike-from-Ottawa, for your kinds words regarding the supplementary photos. I wish everyone did this with their descriptions … I especially wish that Sereno did! Another high-profile Nigersaurus paper and we still only have any real idea what about four of the bones look like. *sigh*

  6. #6 Nick
    November 17, 2007

    ‘Proneneukos’ means something like ‘forward sloping’ and of course refers to one of the neural arch’s most distinctive anatomical features.

    Specifically, proneneukos is the perfect active participle of the Greek verb proneuein, which means ‘to stoop or bend forward’, like a rower in a boat or a rider on a horse.

  7. #7 David Marjanovi?
    November 18, 2007

    So “having bent forward”?

  8. #8 Mark Witton
    November 18, 2007

    Darren and Mike,

    Belated congratulations on the new taxon, the success of the paper and all the fame, money and women it will inevitably send flocking to your doors (there are, after all, no other reasons why palaeontology exists than these last three perks). Of course, I’m especially excited because I’ve been able to tell all the people I’ve overheard buzzing about Xenoposeidon (you know, passers-by on the street, folk in the queues at the post office) that I’m part of the same research group. Good times for our humble department, indeed.

    Oh, and a big pat on the back for the ‘unofficial’ supplementary data. Uploading your Nexus file, high-resolution figures and a plethora of good quality photographs of the specimen is a truly excellent, excellent idea. The amount of data you’ve made available is fantastic, really the next best thing to visiting the NHM and seeing the specimen firsthand. In these digital times there’s little reason why this sort of thing shouldn’t be commonplace: if other people put as much time and effort into disseminating their data as this, the jobs of palaeontologists across the world be so much easier. Gentlemen, my hat is tipped in your direction.

  9. #9 Nick
    November 18, 2007

    David wrote:

    So “having bent forward”?

    Literally, yes.

  10. #10 Michael P. Taylor
    November 19, 2007

    Thanks for your kind words, Mark. Yes, I think that the “unofficial supplementary information” is really important, and I do hope that other authors will increasingly do the same thing. If I had a pound for every time I wished I had good, high-resolution images of some published fossil, then, well, I could afford a good curry and a pint anyway. So I suppose that the three reactions I’ve most hoped for to the Xeno paper are (1) “Ooooh, cool!”, (2) “Sauropods certainly are a lot more diverse and weird and interesting than I gave them credit for”, and (3) “I must remember to post high resolution photos of the next thing I describe”.

  11. #11 Georgios Georgalis
    November 19, 2007

    My Compliments and from me on our new friend Xenoposeidon with just a little comment on the pronunciation, as a Greek speaker :
    it’s pronounced ”Xenoposedon” (in Greek ????????????)
    There is no ‘z’ or ‘y’

  12. #12 David Marjanovi?
    November 19, 2007

    There is no ‘z’ or ‘y’

    English speakers pronounce everything as if it were English.

    And most of them have never got the idea that a word in any language might begin with “ks” (or “ps” or “ts” for that matter).

    And while I am at it, in reality ? is pronounced wng (the accent indicates that the syllable has an inbuilt question mark). ;-) (ScienceBlogs has an interesting font by default…)

  13. #13 Michael P. Taylor
    November 20, 2007

    Hi, Georgios. Thanks for the pronunciation tip, but I didn’t understand how you were saying it should be different from what the paper specifies: “ZEE-no-puh-SYE-d’n”. Could you spell it out phonetically?

    (Just for interest, of course: since it’s published, the pronunciation in the paper is now definitive, whether or not it’s properly transferred from the Greek.)

  14. #14 Nick
    November 20, 2007

    Georgios wrote:

    it’s pronounced ”Xenoposedon” (in Greek ΞΕΝΟΠΟΣΕΙΔΩΝ)
    There is no ‘z’ or ‘y’

    Wouldn’t it be something like [ksenoposiðon] in modern Greek?

    I’m assuming the pronunciation guide is only intended to incicate pronunciation in English, where the pronunciation of word-initial x as [z] is standard.

    The ye in the SYE syllable in the pronunciation guide is intended to represent the diphthong [ai].

  15. #15 Georgios Georgalis
    November 20, 2007

    I just saw the pronunciation in the official paper, that’s why I made this friendly comment!I know it was refering to the english pronunciation,but as it is a Greek name, I thought it would be interesting for you to have a look in the original language!in Greek ”X” is ”?” so it’s spelled ”ks”
    ”ei” is like ‘i’ but not ”ai”!also note that the firt o (xenOposeidon) is omikron so it is short and the second (xenoposeidOn) is ?(omega) so it is long!That’s from me!I hope i didnt make you bored with all this pronunciation and Greek lesson!

  16. #16 Cunzy1 1
    November 22, 2007

    Actually, you clearly have it all wrong. This is the world’s most unremarkable sauropod and all the rest are in the sister group amazing sauropods. Don’t worry I’ll let you publish that reclassification.

    But does it’s unremarkableness make it amazing? Perhaps. You might have grounds for that.

  17. #17 Nick
    November 22, 2007

    also note that the firt o (xenOposeidon) is omikron so it is short and the second (xenoposeidOn) is Ω(omega) so it is long!That’s from me!I hope i didnt make you bored with all this pronunciation and Greek lesson!

    The second o in proneneukOs is also an omega. Note that this -os is not the same as the nominative singular ending -os (which has an omicron).

  18. #18 Harry W. McCormack
    December 13, 2007

    To begin, let me mention that I discovered a race of beings that inhabited the earth, probably before humans were ever contemplated, and that they were sub-miniture in stature. These beings always had to find ways to camoflauge themselves (I don’t know what they were protecting themselves from unless from larger beings or animals that inhabited the earth at the same time) and used all kinds of ingenious ways of doing this. They most always used a netting of some kind…apparently to protect themselves from being seen from above. They had developed a kind of aluminum sheeting they used for roofing and formed it into a “Tee-Pee” type building….the one I have is about 3-4 inches tall, but was stepped on by another larger being that crushed it…this is in the form of a fossil. They had nails and hammers, which was what I saw first and led to this discovery. As I reasearched these beings, I began to see gold nails and have a gold needle with the thread still in it and pushed through a ball of a thread that looks like monifilament fishing line. It can only be viewed through magnification. From these fossils, a 3mm long item dropped and looks like a flying dinosaur, but has a head shaped like a horse. To keep from losing it, it is scotch-taped to a card.

    Now, my comment about the vertebrae of a dinosaur found and discussed in great detail in this article. After much studying of the photos accompanying this article, I find that this is not a vertebrae. It is one of the many ways the beings discussed above had of making articles for their protection. This is why they keep saying they don’t know how to determine what it is. This “vertebrae” was made from various creatures and can be seen when studying it closely. Close examination will show the way it was sewn together and the thread can readily be seen, although they look like veins at first glance. Some of the creatures features can be determined.

    Along these same lines, I have already reported that the “Hand” that was found, severed at the wrist, and had never been able to identify. I reported that it was an abode of some sort for these beings. The little finger that had supposedly been severed, had nails driven around it and were readily visible in the photo.

    I hope my article will give some insight that may lead to your identification of the item you have. It would be great to discuss some of my discoveries with you and maybe with your knowledge we could find out what these beings were and what catastrophic event led to their demise. They all perished in the position they where in as if frozen in time. My photos would help show what these beings are and help show what I’ve been saying about your vertebrae. Let me know if you would like them E-mailed to you at a later time.

    Keep up the good work. Articles like yours are always refreshing. Thanks…

  19. #19 David Marjanovi?
    December 13, 2007

    They all perished in the position they where in as if frozen in time.

    Er… wrong.

    And the singular of vertebrae is vertebra.

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