An important paper is out today: Carpenter (2018) names Maraapunisaurus, a new genus to contain the species Amphicoelias fragillimus, on the basis that it’s actually a rebbachisaurid rather than being closely related to the type species Amphicoelias altus.

Carpenter 2018: Figure 5. Comparison of the neural spine of Maraapunisaurus fragillimus restored as a rebbachisaurid (A), and the dorsal vertebrae of Rebbachisaurus garasbae (B), and Histriasaurus boscarollii (C). Increments on scale bars = 10 cm.

And it’s a compelling idea, as the illustration above shows. The specimen (AMNH FR 5777) has the distinctive dorsolaterally inclined lateral processes of a rebbachisaur, as implied by the inclined laminae meeting at the base of the SPOLs, and famously has the very excavated and highly laminar structure found in rebbachisaurs — hence the species name fragillimus.

Ken’s paper gives us more historical detail than we’ve ever had before on this enigmatic and controversial specimen, including extensive background to the excavations. The basics of that history will be familiar to long-time readers, but in a nutshell, E. D. Cope excavated the partial neural arch of single stupendous dorsal vertebra, very briefly described it and illustrated it (Cope 1878), and then … somehow lost it. No-one knows how or where it went missing, though Carpenter offers some informed speculation. Most likely, given the primitive stabilisation methods of the day, it simply crumbled to dust on the journey east.

Carpenter 2018: Frontispiece. E. D. Cope, the discoverer of AMNH FR 5777, drawn to scale with the specimen itself.

Cope himself referred the vertebra to his own existing sauropod genus Amphicoelias — basically because that was the only diplodocoid he’d named — and there it has stayed, more or less unchallenged ever since. Because everyone knows Amphicoelias (based on the type species A. altus) is sort of like Diplodocus(*), everyone who’s tried to reconstruct the size of the AMNH FR 5777 animal has done so by analogy with Diplodocus — including Carpenter himself in 2006, Woodruff and Foster (2014) and of course my own blog-post (Taylor 2010).

(*) Actually, it’s not; but that’s been conventional wisdom.

Ken argues, convincingly to my mind, that Woodruff and Foster (2014) were mistaken in attributing the great size of the specimen to a typo in Cope’s description, and that it really was as big as described. And he argues for a rebbachisaurid identity based on the fragility of the construction, the lamination of the neural spine, the extensive pneumaticity, the sheetlike SDL, the height of the postzygapophyses above the centrum, the dorsolateral orientation of the transverse processes, and other features of the laminae. Again, I find this persuasive (and said so in my peer-review of the manuscript).

Carpenter 2018: Figure 3. Drawing made by E.D. Cope of the holotype of Maraapunisaurus fragillimus (Cope, 1878f) with parts labeled. “Pneumatic chambers*” indicate the pneumatic cavities dorsolateral of the neural canal, a feature also seen in several rebbachisaurids. Terminology from Wilson (1999, 2011) and Wilson and others (2011).

If AMNH FR 5777 is indeed a rebbachisaur, then it can’t be a species of Amphicoelias, whose type species is not part of that clade. Accordingly, Ken gives it a new generic name in this paper, Maraapunisaurus, meaning “huge reptile” based on Maraapuni, the Southern Ute for “huge” — a name arrived at in consultation with the Southern Ute Cultural Department, Ignacio, Colorado.

How surprising is this?

On one level, not very: Amphicoelias is generally thought to be a basal diplodocoid, and Rebbachisauridae was the first major clade to diverge within Diplodocoidae. In fact, if Maraapunisaurus is basal within Rebbachisauridae, it may be only a few nodes away from where everyone previously assumed it sat.

On the other hand, a Morrison Formation rebbachisaurid would be a big deal for two reasons. First, because it would be the only known North American rebbachisaur — all the others we know are from South America, Africa and Europe. And second, because it would be, by some ten million years, the oldest known rebbachisaur — irritatingly, knocking out my own baby Xenoposeidon (Taylor 2018), but that can’t be helped.

Finally, what would this new identity mean for AMNH FR 5777’s size?

Carpenter 2018: Figure 7. Body comparisons of Maraapunisaurus as a 30.3-m-long rebbachisaurid (green) compared with previous version as a 58-m-long diplodocid (black). Lines within the silhouettes approximate the distal end of the diapophyses (i.e., top of the ribcage). Rebbachisaurid version based on Limaysaurus by Paul (2016), with outline of dorsal based on Rebbachisaurus; diplodocid version modified from Carpenter (2006).

Because dorsal vertebrae in rebbachisaurids are proportionally taller than in diplodocids, the length reconstructed from a given dorsal height is much less for rebbachisaurs: so much so that Ken brings in the new version, based on the well-represented rebbachisaur Limaysaurus tessonei, at a mere 30.3 m, only a little over half of the 58 m he previously calculated for a diplodocine version. That’s disappointing for those of us who like our sauropods stupidly huge. But the good news is, it makes virtually no difference to the height of the animal, which remains prodigious — 8 m at the hips, twice the height of a giraffe’s raised head. So not wholly contemptible.

Exciting times!

References

 

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I’m delighted to announce the publication today of my new paperXenoposeidon is the earliest known rebbachisaurid sauropod dinosaur”. This is the peer-reviewed version, in my favourite journal PeerJ, of the manuscript that became available as a preprint eight months ago — which was in turn a formalisation of a blog-post from 2015.

Taylor (2018: Figure 3). Autapomorphies of Xenoposeidon proneneukos NHMUK PV R2095, mid-posterior dorsal vertebra, highlighted in red. A. anterior view. B. left lateral view. Numbers pertain to the numbering of autapomorphies in the text. 1a, neural arch covers whole of centrum, and 1b is contiguous with posterior articular facet. 2, neural arch is inclined forward by 30–35 degrees relative to the vertical. 3a, inclined ridge-like lamina marks ventral margin of 3b broad featureless area of bone. 4, large teardrop-shaped anterior fossa. 5a, vaulted laminae bound this fossa, but are not the medial CPRLs (5b, drawn in finer lines), which continue up to the presumed location of the prezygapophyses.

In a sense, then, this paper is old news. It doesn’t contain any startling new insights that readers of this blog wouldn’t already have been aware of. But it’s become more rigorous, better argued and justified, better illustrated (the image above is one of two new figures), and generally toughened in the forge of peer-review. It’s also now, of course, officially part of the scientific record.

I’m delighted about this paper for several reasons. First, of course, because Xenoposeidon is a beautiful specimen and now turns out to be rather more important than I’d previously realised. Second, because I hope this paper’s inclusion of the high-resolution full-colour 3D model as a supplementary file will help to establish this as common practice. But also third, because it’s my first paper in ages.

In fact, if you were being harsh, you could say it’s my first real paper since the annus mirabilis of 2013 when Matt and I had four good, solid papers come out in a single year. My CV lists five papers between then and now, but a case can be made that none of them really count:

  • Taylor 2014 is essentially an addendum to my and Matt’s PLOS ONE paper the year before.
  • Upchurch et al. 2105 is a significant and substantial piece of work, but almost all the credit on that one is due to Paul and Phil.
  • Taylor 2016 is more of an advocacy piece than a scholarly paper.
  • Ansolabehere et al. 2016 is merely a report summarising a multi-day discussion, and I am in any case only one of nine(!) co-authors.
  • Taylor 2017 is just a short comment on someone else’s ICZN petition. (In fact that one is so feeble I should just remove it from my CV.)

Putting it all together, it’s been the best part of five years since I made a significant contribution to the scientific record, and to be honest I was starting to wonder whether I could still do it. (My deep thanks go to Paul Upchurch and Phil Mannion for keeping my publication record on life-support with that Haestasaurus paper!)

The challenge for me now is, having got back on the horse, to ride it hard. In particular:

That’s not even mentioning other long-in-the-works projects like the descriptions of Apatosaurusminimus and “Biconcavoposeidon”. Sheesh. I’m so lazy. Nearly as bad as Darren.

References

 

There’s just time before midnight strikes to wish Xenoposeidon a very happy tenth birthday. It came along just a month and a half after SV-POW! itself — in fact, I can’t even remember now, a decade on, whether part of the reason we started SV-POW! in the first place was so we’d have somewhere to talk about it when the paper (Taylor and Naish 2007) came out.

Taylor 2017: Figure 4. NHMUK R2095, the holotype and only vertebra of Xenoposeidon proneneukos, in left lateral view, interpreted as a rebbachisaurid. This interpretation is modelled primarily on MNHN MRS 1958, a posterior dorsal vertebra from the holotype specimen of Rebbachisaurus garasbae. The CPOL passes through a sheetlike PCDL, as in Rebbachisaurus; but the lateral CPRL forms a cross-shaped junction with the ACPL, each of these laminae equally interrupting the trajectory of the other. Abbreviations as used in the text. Scale bar = 200 mm.

For the last few days, I have been working away like a trojan, trying to ready a new manuscript for launching on this day. I’ve taken two days off from my day-job to get it done before this arbitrary deadline, and here I am writing about it with just 15 minutes to go!

The title of this new manuscript (Taylor 2017) is “Xenoposeidon is the earliest known rebbachisaurid sauropod dinosaur”, and it explains in detail the argument that I made informally sixteen months ago when I first saw the rotating video of the Rebbachisaurus garasbae that Jeff Wilson and co put out with their then-new redescription of that species. I got it submitted (to PeerJ, natch) a bit more than an hour ago, and at the same time I clicked the “Make this available as a preprint” button. So as I write this, I am periodically checking back in the other window to see whether it’s made it through the basic editorial checks yet.

The thing is, I really love Xenoposeidon. I admit that a surprising number of people (my wife, Matt, his wife, Heinrich Mallison, his wife) seem to think it looks like a turd. But I honestly think it’s the most beautiful single bone I’ve ever seen. It’s a privilege to work on it.

Taylor 2017: Figure 5. NHMUK R2095, the holotype and only vertebra of Xenoposeidon proneneukos, in left anteroventrolateral view, highlighting the three sets of laminae related to the prezygapophyses. The trajectories of the medial CPRLs (which emerge from the neural arch pedicels) and the lateral CPRLs (which intersect with the APCLs) indicate the approximate position of the prezygapophyses. The additional arched laminae form the margins of the large, teardrop-shaped CPRF, but meet at a position some way below and posterior to the presumed location of the prezygapophyseal facets. Breakage of both medial CPRLs and the left ACPL and PCDL is indicated by cross-hatching. Note that, from this perspective, the lateral CPRL appears to turn a corner where it intersects with the ACPL, such that the posteroventral portion of the lateral CPRL appears contiguous with the dorsal portion of the ACPL. This is an illusion brought about by the eminence at the point of intersection. As always, this is much easier to see in three dimensions. Abbreviations as used in the text.

Anyway, I’ll link to the preprint as soon as it’s up. In the mean time, I’m just going to bask in the beauty that is Xenoposeidon.

Immediate update

Four minutes after posting this, and just three minutes before midnight, I got the notification from PeerJ that the preprint is up! So you are welcome to leave comments about the science on that page if you wish: I will take them into account when I revise the manuscript in light of the formal peer-reviews that will be coming along in due time.

References

 

Just got the APP new issue alert and there are three papers that I think readers of this blog will find particularly interesting:

That’s all for now, just popping in to let people know about these things.

Now that the new Wilson and Allain (2015) paper has redescribed Rebbachisaurus, we can use it to start thinking about some other specimens. Particularly helpful is this beautiful rotating animation of the best dorsal vertebra (here captured at the point of the rotation where we’ve viewing it in right anterolateral):

rebbachisaur-dorsal-rotation

As I briefly discussed on Twitter, seeing this made me think of my baby, Xenoposeidon. Now that specimen, beautiful though it is, preserves only the lower one third of the vertebra. But there are some clear commonalities, and they’re clearer if you look at the animation.

Xenoposeidon-TNF

Most obviously, there are laminae running up and down the anterior and posterior margins of the lateral face of Xeno’s neural arch, and those same laminae seem to exist in Rebbachisaurus. We didn’t name these laminae in the Xeno paper, but if they’re the same thing as in Rebbachisaurus, then they’re ACPLs and PCDL — anterior centroparapophyseal and posterior centodiapophyseal laminae.

If that’s right, then we misinterpreted the site of the parapophysis in Xenoposeidon. We (Taylor and Naish 2007) thought it was at the cross-shaped junction of laminae near the anterodorsalmost preserved part of the vertebra. In Rebbachisaurus, this cross exists, but it’s merely where the CPRL (centroprezygapophyseal lamina) intersects the ACPL.

But there’s more. In Xenoposeidon, the base of the CPRL (if that’s what it is) forms a “V” shape with an accessory lamina that proceeds posterodorsally from the same origin. (This is one of the features that’s apparent on the more damaged right side of Xeno as well as the nicer left side.) That lamina also seems to exist in Rebbachisaurus — but with the whole vertebra to consider, we can see that it’s not an accessory lamina, but a perfectly well-behaved CPOL (centropostzygapophseal lamina).

So if Xeno is indeed a rebbachisaurid, then the two branches of the “V” go to support the pre- and postzygs, and the laminae running up the anterior and posterior margins of the centrum support the parapophyses and diapophyses respectively. There are actually two crosses on each side of the neural arch: one at the intersection of CPRL and ACPL, the other at the intersection of CPOL and PCDL; but in the Xeno specimen, the posterior cross is lost, having been just above where the break occurs at the top of the neural arch.

Here’s what I mean:

reconstructed-as-rebbachisaur

In case it’s not clear, the grey lines are an (extremely crude) reconstruction, the blue lines label the important laminae, and the red circles highlight the two crosses.

Hmm. The more I look at this, the more convincing I find it.

But there’s more! The anterior aspect of the Rebbachisaurus vertebra also bears a notable resemblance to what we see in Xeno, with a pair or arched laminae forming a vaulted roof to the neural canal.

 

rebbachisaur-dorsal-rotation2

Jeff Wilson spotted the same thing in a sequence of comments on my tweets, saying:

That’s not a bad call—the infrazygapophyseal region of that vert is elongate, and there is a nice CPRF and those closely positioned TPRLs could mean that prz’s are close to one another or even conjoined. It’s tantalizing, but not much to go on. Would be nice to prep out CPRF & work out laminae on lat sfc.

Jeff is right that more preparation would help to figure this out.

Not that everything about the Rebbachisaurus dorsal is Xeno-ish. Most notably, the lateral foramen is nothing like that of Xeno, being an uninspiringly dull and simple oval rather than the much more elegant foramen-within-a-fossa arrangement that we see in Xeno. But there are other points of commonality, too, such as the flat stretch of bone above the fossa and the way the posterior margin of the neural arch reaches the posterior margin of the centrum.

All in all — while there is plenty of work yet to do — I am increasingly inclined to think that the evidence we currently have suggests Xenoposeidon is a rebbachisaurid. If that’s right, it would be quite an exciting result. It would be the earliest known rebbachisaur, and the only named one from the UK. (Mannion 2009 described, but did not name, a rebbachisaurid scapula from Wessex formation of the Wealden). Could Mannion’s scapula be Xenoposeidon? Unlikely, as it’s 10 million years more recent. But it could be a close relative.

Exciting times!

References

 

Sauropod guru Jeff Wilson is on Twitter, as of a couple of weeks ago. In one of his earliest tweets, he showed the world this gorgeous photo of a Rebbachisaurus dorsal:

Jeff Wilson (left) and Ronan Allain (right), with dorsal vertebra of Rebbachisaurus.

Jeff Wilson (left) and Ronan Allain (right), with dorsal vertebra of Rebbachisaurus. Photograph by MNHN photographer, Copyright © Muséum National d’Histoire Natural.

I’m pretty certain this is the dorsal vertebra that’s been on exhibition in Paris for some time, and which is part of the holotype of Rebbachisaurus garasbae, which is in turn the type specimen of Rebbachisaurus and so of Rebbachisauridae as a whole. In which case it’s pretty darned important as defining a major group of sauropods.

This specimen was initially described, very briefly and without illustrations, by Lavocat (1954). The species (though a different specimen) was given a slightly better treatment by Russell (1996), as part of a larger work on isolated dinosaur bones. Russell included some line-drawings of the material (his figures 29-31), of which the pick is definitely this one of the bottom part of a dorsal vertebra:

xx

Rebbachisaurus garasbae, NMC 50844, anterior dorsal vertebra in (a) right lateral, (b) anterior, (c) left lateral and (d) posterior aspect. From Russell (1996:figure 30).

As noted by Russell (p388), this vertebra is similar, but not identical, to the one in Wilson’s photo. Russell says of his specimen that “the greater length of the centrum relative to the height and width of the intercentral articulations and less steeply projecting transverse processes imply that the vertebra occupied a more anterior position in the column.”

Will Rebbachisaurus ever get the detailed treatment that such gorgeous material deserves? Yes! here’s another tweet from Jeff:

Fantastic to think that Rebbachisaurus is in the works, and Nigersaurus to follow! Happy days!

References

  • Lavocat, R. 1954. Sur les Dinosauriens du continental intercalaire des Kem-Kem de la Daoura. [On the dinosaurs of the Continental Intercalaire of the Kem Kem of the Daoura].Comptes Rendus 19th Intenational Geological Congress 1952 (1):65-68. [English translation]
  • Russell, D.A. (1996). Isolated dinosaur bones from the Middle Cretaceous of the Tafilalt, Morocco. Museum Natl. d’Histoire Nat. (Paris) Bull. Ser. 4 18 (Section C, Nos. 2-3), 349-402.

Here is Tataouinea, named by Fanti et al. (2013) last week — the first sauropod to be named after a locality from Star Wars (though, sadly, that is accidental — the etymology refers to the Tataouine Governatorate of Tunisia).

FantiEtAl2013-tataouinea-fig3

Fanti et al. (2013: figure 3) T. hannibalis selected elements and reconstruction. (a) Sacral neural arches 1-3, right lateral view; (b) sacral neural spine 4, right lateral view; (c) sacral neural spine 5, right lateral view; (d) caudal vertebra 2 and fragment of caudal 1 postzygapophyses, left lateral view; (e) caudal vertebra 1, left lateral view; (f) sacral centrum 1, ventral view; (g) sacral centra 2-5, ventral view; (hj) caudal vertebra 3, anterior (h), left lateral (i), posterior (j) views; (k) left ilium, lateral view; (l) right ischium, medial view; and (m) skeletal reconstruction of T. hannibalis. Missing elements based on other nigersaurines. Scale bar: 10 cm (a-l), 1 m (m). a, acetabulum; f, fossa; hr, hyposphenal ridge; ip, ischial peduncle; ll, lateral lamina; pf, pneumatic foramen; pl, pleurocoel; poz, postzygapophysis; pp, pubic peduncle; psdf, prezygospinodiapophyseal foramen; sdl, spinodiapophyseal lamina; spol, spinopostzygapophyseal lamina; spzl, spinoprezygapophyseal lamina; sr, sacral rib; tp, transverse process. The asterisk indicates the fossa bounded by the spzl and the sdl.

No doubt Matt willl have much more to say about this animal, and especially its pneumatic features. I just thought it was time for a picture-of-the-week post.

UPDATE: Matt here, just a few quick thoughts (I’m in the middle of my summer anatomy lectures so they will be less extensive than this animal deserves). First, it’s awesome to see so much pneumaticity, and in elements that have not previously been reported as pneumatic in sauropods. The authors make a good case that we’re looking at actual pneumaticity here, for example in the pelvic elements, and not something else. So that’s cool.

What’s even cooler is that we’re seeing this in a diplodocoid:  Tataouinea is a rebbachisaurid. We’ve seen extreme pneumaticity in saltasaurines, and now we’ve got a parallel evolution of this character complex in diplodocoids. That’s cool by itself, and it’s further evidence that the underlying generating mechanism–the air sacs and their diverticula–were all in place long before they started leaving traces on the skeleton. The case for a birdlike lung-air sac system in sauropods, in saurischians, and in ornithodirans generally only keeps getting stronger. That is, we’re seeing more evidence not just that air sacs were there, but that they were bird-like in their layout, e.g., pneumatization of the pectoral girdle by clavicular air sacs, in both saltasaurines and theropods (avian and otherwise), and now extensive pelvic pneumatization (i.e., going beyond what we’ve seen previously in saltasaurines) by abdominal air sacs in rebbachisaurids and theropods (and pterosaurs, can’t forget about them). Happy times.

Reference

Fanti, Federico, Andrea Cau, Mohsen Hassine and Michela Contessi. 9 July 2013. A new sauropod dinosaur from the Early Cretaceous of Tunisia with extreme avian-like pneumatization. Nature Communications 4:2080. doi:10.1038/ncomms3080