In a comment on the initial Shunosaurus tail-club post, Jaime Headden pointed out the passage in the Spinophorosaurus paper (Remes et al. 2009) that discusses the club of Shunosaurus (as justification for positioning the Spinophorosaurus osteoderms on the end of its tail):
With the holotypic skeleton, two closely associated dermal ossifications were found originating from contralateral sides (Fig. 4A–C). These elements have a subcircular base that is rugose and concave on its medial side, and bear a caudodorsally projecting bony spike with a rounded tip laterally. Although these elements were found in the pelvic region under the dislocated scapula, we regard it as most probable that they were placed on the distal tail in the living animal for the following reasons: First, the close association of the contralateral elements indicates they were originally placed near the (dorsal) midline of the body. Second, the stiffening of the distal tail by specialized chevrons is also found in other groups of dinosaurs that exhibit tail armor [42,43]. Third, osteoderms of similar shape are known from the closely related basal eusauropod Shunosaurus . In the latter form, these elements cover the middle part of a tail club formed by coalesced distal vertebrae; however, the decreasing size of the distal-most caudal vertebrae of Spinophorosaurus indicate that such a club was not present in this genus. The right osteoderm is slightly larger and differs in proportions from the left element, indicating that, as in Shunosaurus , originally two pairs of tail spines were present (Fig. 5).
– Remes et al. (2009:6-8)
And this gives the reference that I needed for the Shunosaurus tail-spikes (as opposed to the club) — reference 26 is Zhang (1988), which, embarrassingly, we’ve featured here on SV-POW! in our first Shunosaurus post. Evidently I was so focussed on preparapophyses when I looked at that monograph that I completely failed to register the tail-club spikes — but then, which of us can truly say he has not made that mistake?
Anyway, here’s what Zhang has to show us:
And here’s that tail again, this time from the poorly reproduced photographic plate 12, part 1, and in right lateral view:
It’s apparent that this really is the other side of the distal tail (rather than a reversed image of the same side) because the osteoderms are in front of the club vertebrae in the left-lateral figure, but behind them in the right-lateral plate.
It would be great to say more about these, but the English language summary of Zhang’s monograph is understandably brief, constituting six pages of the 90. What’s not quite so understandable is that neither the diagnosis of the genus Shunosaurus nor that of the species S. lii mentions the tail-club or spikes, which are arguably the most distinctive features. The “revised diagnosis” on pp. 78-79 does, however — just:
Posterior caudals platycoelous, with small cylindrical centra; neural spines low, rod-like. In several last caudals swollen ralidly [sic] and forming “tail-mace”; in addition there are two pairs of little caudal spines, being analogous to that of stegosaurs.
Not much to go on, but something. That’s all, though — there is no further description, and crucially, no indication of whether the tail elements were found articulated or whether the spikes were found isolated and subsequently moved to the end of the tail. It may be that Remes at al. know something I don’t, of course — they might have a translation of Zhang (1988) — but if not, then it’s amusing to consider that the spikes on the tail of Shunosaurus may or may not be supported by evidence, and that the inference of tail-spikes on Spinophorosaurus might be based on dodgy premises.
The other thing that struck me forcibly, as I looked at the figure and plate above, is that the caudal vertebrae remain fairly complex all the way to the end: they retain distinct and prominent neural spines, unlike the distal caudal vertebrae of diplodocids and brachiosaurs. I notice that the distal caudals of Spinophorosaurus also seem to be complex, based on fig. 3H-I and also on the skeletal reconstruction that is fig. 5 — both of which we’ve reproduced before, in our old Spinophorosaurus article.
So what’s going on here? Are Shunosaurus and Spinophorosaurus unusual in having distal caudals that retain complex neural spines? If so, is this property correlated with the possession of a tail-club and/or spines? Is it causally related? Or could it be that this is normal for basal eusauropods, and my ideas of sauropod tails have been too coloured by extreme neosauropodocentricity? Clearly I ought to go and look at a lot more basal sauropods’ distal tails before publishing this post. And prosauropods’, theropods’, ornithischians’, pterosaurs’, crocadilians’ and lizards’ distal tails.
As it happens, the one non-neosauropod group of reptiles whose distal tails I do know something about is monitor lizards, thanks to my adventures with the corpse of “Charlie”. And those caudals do maintain astonishingly detailed structure right to the end of the tail, with even absolutely tiny caudals having distinct processes. Here are some photographs that show this.
First, one showing all 56 caudal vertebrae (the 1st is half in frame at top right, next to the sacrum; the rest read from left to right on successive rows, like words on a page).
Now here are five representative caudals from different regions on the tail — the last ones from each row in the picture above, as it happens: caudals 1, 10, 21, 30, 42 and 56. They are in more or less dorsal view, though caudal 1 has fallen forward onto its anterior face. In this and subsequent pictures, caudal 10 (the second shown) is for some reason back to front.
Now here are the same vertebrae, in the same order and orientation, but now in left dorsolateral aspect (except caudal 10 which is of course in right dorsolateral):
Finally, here are the three smallest of these vertebrae (numbers 30, 42 and 56) in close-up, again in left dorsolateral view, so you can more easily see how much structure even the distalmost caudal has:
That last caudal is about 2.5 mm long.
(It’s interesting that caudals 30 and 42 have those cute fused chevrons.)
So anyway: we know that caudal vertebrae retain distinct structure all the way down to the tip of the tail in monitor lizards at least some basal eusauropods: could it be that this is the primitive state, and that degenerate caudals are found only in neosauropods and mammals? Gotta prep out some more animals’ skeletons and find out!
- Remes, Kristian, Francisco Ortega, Ignacio Fierro, Ulrich Joger, Ralf Kosma, Jose Manuel Marin Ferrer, for the Project PALDES, for the Niger Project SNHM, Oumarou Amadou Ide, and Abdoulaye Maga. 2009. A new basal sauropod dinosaur from the Middle Jurassic of Niger and the early evolution of Sauropoda. PLoS ONE 4(9):e6924. doi:10.1371/journal.pone.0006924
- Zhang Yihong. 1988. The Middle Jurassic dinosaur fauna from Dashanpu, Zigong, Sichuam, vol. 1: sauropod dinosaur (I): Shunosaurus. Sichuan Publishing House of Science and Technology, Chengdu, China.
A comment by Charles Epting on the recent article about self-publication led me to check the relevant section of the draft Phylocode, which I’ve read once or twice before but not recently enough for this to have hit me with the force it ought:
From Chapter II. Publication, and specifically Article 4. Publication Requirements:
4.2. Publication, under this code, is defined as distribution of text (but not sound), with or without images. To qualify as published, works must be peer-reviewed, consist of numerous (at least 50 copies), simultaneously obtainable, identical, durable, and unalterable copies, some of which are distributed to major institutional libraries (in at least five countries on three continents) so that the work is generally accessible as a permanent public record to the scientific community, be it through sale or exchange or gift, and subject to the restrictions and qualifications in the present article.
4.3. The following do not qualify as publication: (a) dissemination of text or images solely through electronic communication networks (such as the Internet) or through storage media (such as CDs, diskettes, film, microfilm and microfiche) that require a special device to read.
I am … flabbergasted, if that’s the word I want. (I always want to spell that with an “h” after the “g”.) This language is obviously derived from what’s in the ICZN — for example, “must have been produced in an edition containing simultaneously obtainable copies by a method that assures numerous identical and durable copies” becomes “must consist of numerous (at least 50 copies), simultaneously obtainable, identical, durable, and unalterable copies”.
And the result is that, just like the ICZN, the draft Phylocode does not recognise electronic publication.
Just think about that. It means that if you define a clade in most of the PLoS journals, it won’t count (unless the journal does one of its inkjet-and-staples special print runs for you). It also means that any clades you define in Proceedings of the Royal Society of London will not count when the initial online article is published, but only when the later printed edition comes out. In other words, it means that both the science journals that are growing most quickly in influence and prestige and the oldest science journal in the world will both be useless for phylogenetic nomenclature.
I am sure that’s not what the Phylocode authors want.
That’s particularly true in light of the code’s further requirement that in order to be valid, clade definitions need to be registered. Really, once a name is officially registered in the Phylocode database and its definition is in a paper published by a reputable publisher and existing in thousands of bit-for-bit-identicial copies in every country in the world, what else is needed for stability? Fifty stapled inkjet copies?
It seems particularly startling in light of the fact that even the notoriously slow-moving ICZN seems now to be recognising that electronic publishing is inevitable; it would be pretty horrible if by the time the Phylocode is finally implemented, the ICZN has accepted its electronic publishing amendment and the Phylocode is seen to be trailing behind the ICZN in recognising the reality of the world we live in. (For anyone who is not yet convinced of that reality, I recommend *cough* Taylor 2009, which is a pleasantly easy read.)
Is it too late? Can the Phylocode be fixed before it’s implemented? Can it just be done, or will it need lengthy discussion first? If this doesn’t get fixed, will anyone take the Phylocode seriously? Is there even a serious argument for keeping the Article 4.2 language as it is now?
I don’t know the answers to any of these questions. Does anyone else out there?
In other news …
I am astounded at the lack of response to University of California vs. Nature, which seems to me just about the most significant thing that’s happened in the world of academic literature since, well, forever. Can it really be that everyone else’s response is, and I quote, “meh”?
- Curry Rogers, K. 2009. The postcranial osteology of Rapetosaurus krausei (Sauropoda: Titanosauria) from the Late Cretaceous of Madagascar. Journal of Vertebrate Paleontology 29(4):1046-1086.
- Taylor, Michael P. 2009. Electronic publication of nomenclatural acts is inevitable, and will be accepted by the taxonomic community with or without the endorsement of the Code. Bulletin of Zoological Nomenclature 66(3):205-214.
June 11, 2010
What’s the deal with most Shunosaur “life restorations” showing spikes on the tail club? I can’t find a picture anywhere of a skeleton with any indication of spikes, and yet almost every fleshed-out illustration of Shunosaurs has spikes on it’s tail. Anybody know what that’s about?
It seems we’ve never actually featured the famous Shunosaurus tail-club here before — an amazing oversight, and one that I’m going to remedy right now, thanks to Dong et al. (1989). This short paper is written in Chinese, so I can’t tell you anything beyond what’s in the figures, captions and English-language abstract.
First up, though, here is his illustration of the famed tail-club:
I can’t help noticing, though, that although the fused clump of enlarged distal caudal vertebrae constitutes a nice club, it’s noticably devoid of spikes. So it remains a mystery why so many restorations show a spiked club. Anyone out know why?
Dong et al. (1989) also obligingly includes a figure of the tail-club of Omeisaurus:
And also a photographic plate showing both clubs (though, as is so often the case, the scan has lost a lot of details):
Now, the big question is: why do Shunosaurus and Omeisaurus — and Mamenchisaurus, for that matter — have tail-clubs when they are not closely related, according to modern phylogenies such as those of Wilson (2002) and Upchurch et al. (2004)? [To be precise, Wilson (2002:fig. 13) had Omeisaurus and Mamenchisaurus clading together, but that clade well separated from Shunosaurus; and Upchurch et al. (2004:fig. 13.18) had all three separate, though with the former two as consecutive branches on the paraphyletic sequence leading to Neosauropoda.]
One possibility is just sheer coincidence: but it’s asking a lot to believe that of the 150 or so known sauropods, the only three for which tail-clubs are known just happened to live more or less at the same time and in the same place.
Another option is some oddity in the environment that strongly encouraged the evolution of tail clubs. Yes, this is wildly hand-wavy, but you can sort of imagine that maybe all the local theropods thought it was cool to hunt sauropods by biting their tails, and the clubs evolved in response to that. Or something. There’s a similar, but even more mystifying, situtation in the late Early Cretaceous Sahara, where the theropod Spinosaurus, the ornithopod Ouranosaurus and arguably even the sauropod Rebbachisaurus all evolved sails. Why then? When there? No-one knows and no-one’s even advanced a hypothesis so far as I know.
Getting back to Jurassic Chinese sauropod tail-clubs, though, there is a third option: could it possibly be that Shunosaurus, Omeisaurus and Mamenchisaurus all form a clade together after all, as proposed back in the day by Upchurch (1998:fig. 19)? Upchurch’s pioneering (1995, 1998) analyses both recovered a monophyletic “Euhelopodidae” — a clade of Chinese sauropods that included the three genera above plus the early Cretaceous Euhelopus, also from China. The existence of this clade was one of the two major points of disagreement between Upchurch’s and Wilson’s phylogenies (the other being the position of the nemegtosaurids, Nemegtosaurus and Quaesitosaurus, which Upchurch placed basally within Diplodocoidea but Wilson recovered as titanosaurs).
Upchurch himself has abandoned the idea of the monophyletic Euhelopodidae, as seen in that 2004 analysis and also in Wilson’s and his joint (2009) reassessment of Euhelopus: everyone now agrees that Euhelopus is a basal somphospondyl, i.e. close to Titanosauria, which is a looong way from the basal position that the other Chinese sauropods hold within Sauropoda.) And so the name Euhelopodidae is no longer used. But could it be that Upchurch was half-right, and that when Euhelopus is removed that the group that was named after it, a clade remains?
[If so, then that clade is called Mamenchisauridae: as noted by Taylor and Naish (2007), this name was coined by Young and Zhao (1972) and so has priority over the Omeisauridae of Wilson (2002), as Wilson himself now recognises. Mamenchisauridae was phylogenetically defined (or, as they have it, "diagnosed") by Naish and Martill (2007:498) as "all those sauropods closer to Mamenchisaurus constructus Young, 1954 than to Saltasaurus loricatus Bonaparte".]
As already noted, Omeisaurus and Mamenchisaurus are close together in the recent analyses of both Upchurch and Wilson, so the question becomes: how many additional steps are required to recover Shunosaurus as a member of their clade rather than in its usual more basal position (in the the case of Upchurch’s analysis, to move Omeisaurus up a node)? And to this, I do not know the answer — to the best of my knowledge, it’s never been tested (or if it has, the result has never been published). I’d test it myself, but I need to stop working on this post and watch Inca Mummy Girl soonest. If , say, 20 additional steps are needed, then forget it. But if we only need, say, three steps, then maybe someone should look at this more closely. Back in 2004, when he was Young And Stupid, Matt Wedel wrote to me, in a private email which I now quote without permission because I am pretty sure he’s not going to sue me:
Now that I’ve defended the status quo [of using unweighted characters in cladistic analysis], there are some things I’d be happy to bend the rules for. If an Omeisaurus pops up with a tail club, then Wilson and Sereno be damned, Omeisaurus and Shunosaurus belong in the same clade. [...] So my final word is unweighted characters, please, except for sauropod tail clubs.
Food for thought.
Finally, I leave you with the skeletal reconstruction of Omeisaurus from Dong et al. (1989:fig 3). Long-time readers will notice a more than passing resemblance to the reconstruction from He et al. (1988:fig. 63), which you can see in Omeisaurus is Just Plain Wrong.
It looks very much as though Dong et al. produced their reconstruction by flipping that of He et al. horizontally and pasting on a tail-club. Well, we can’t hold that against them — I’d have done the same.
- Dong Zhiming, Peng Guangzhao and Huang Daxi. 1988. The Discovery of the bony tail club of sauropods. Vertebrata PalAsiatica 27(3):219-224.
- He Xinlu, Li Kui and Cai Kaiji. 1988. The Middle Jurassic dinosaur fauna from Dashanpu, Zigong, Sichuan, vol. IV: sauropod dinosaurs (2): Omeisaurus tianfuensis. Sichuan Publishing House of Science and Technology, Chengdu, China. 143 pp. + 20 plates.
- Naish, Darren, and David M. Martill. 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. (Bicentennial Review issue.)
- Taylor, Michael P. and Darren Naish. 2007. An unusual new neosauropod dinosaur from the Lower Cretaceous Hastings Beds Group of East Sussex, England. Palaeontology 50 (6): 1547-1564. doi: 10.1111/j.1475-4983.2007.00728.x
- Upchurch, Paul. 1995. The evolutionary history of sauropod dinosaurs. Philosophical Transactions of the Royal Society of London Series B, 349: 365-390.
- Upchurch, Paul. 1998. The phylogenetic relationships of sauropod dinosaurs. Zoological Journal of the Linnean Society 124: 43-103.
- Upchurch, Paul, Paul M. Barrett and Peter Dodson. 2004. Sauropoda. pp. 259-322 in D. B. Weishampel, P. Dodson and H. Osmólska (eds.), The Dinosauria, 2nd edition. University of California Press, Berkeley and Los Angeles. 861 pp.
- Wilson, Jeffrey A. 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136: 217-276.
- Wilson, Jeffrey A. and Paul Upchurch. 2009. Redescription and reassessment of the phylogenetic affinities of Euhelopus zdanskyi (Dinosauria – Sauropoda) from the Early Cretaceous of China. Journal of Systematic Palaeontology 7: 199-239. doi:10.1017/S1477201908002691
- Young, Chung-Chien, 1954. On a new sauropod from Yiping, Szechuan, China. Acta Palaeontologica Sinica II(4):355-369.
- Young, Chung-Chien, and X. Zhao. 1972. [Chinese title. Paper is a description of the type material of Mamenchisaurus hochuanensis]. Institute of Vertebrate Paleontology and Paleoanthropology Monograph Series I, 8:1-30. English translation by W. Downs.
March 30, 2010
In color, this time, with multiple views, thanks to Xing et al. (2009). They also did a finite element analysis of the tail club and concluded that it was a fairly pathetic weapon. Xing et al. closed by supporting the contention of Ye et al. (2001) that the tail club was a sensory organ. As they stated at the end of the abstract:
The tail club of Mamenchisaurus hochuanensis probably also had limitations as a defense weapon and was more possibly a sensory organ to improve nerve conduction velocity to enhance the capacity for sensory perception of its surroundings.
One thing Xing et al. (2009) cite in support of this is the expanded neural canal inside the club, which they compare to the sacral enlargement in stegosaurs and to the glycogen bodies of birds. They rule out a glycogen body on the grounds that the sacral enlargement in stegosaurs is much bigger than the brain volume, whereas the neural canal enlargement in the M. hochuanensis tail club is much smaller (if you don’t follow that logic, don’t worry, neither do I).
I’m not sure what to make of this thing. On one hand, it would be nice to have more than one club available to rule out the possibility that it’s just a weird paleopathology. On the other hand, it looks oddly regular to be pathological, and the definitive clubs in Shunosaurus and Omeisaurus are at least weak support for this being a genuine feature, although the clubs of the former taxa look very different.
Furthermore, I don’t understand how the authors can rule out the presence of a glycogen body based on the size of the neural expansion alone–especially since the functions of glycogen bodies in extant taxa are very poorly understood (as you may remember from this dustup). Nor can I fathom how a titchy little nerve bundle–if such existed–down at the end of the tail could do much to improve nerve conduction velocity up the rest of the tail. Either my understanding of neuroscience is completely shot, or this hypothesis…lacks support. I am open to being enlightened either way.
Finally, I am disappointed that the authors didn’t pursue the cutting-edge pseudohead hypothesis that has figured prominently here and elsewhere in the blogosphere. There’s a Nobel lurking in there, I just know it.
- Xing, L, Ye, Y., Shu, C., Peng, G., and You, H. 2009. Structure, orientation, and finite element analysis of the tail club of Mamenchisaurus hochuanensis. Acta Geologica Sinica 83(6):1031-1040.
- Ye, Y., Ouyang, H., and Fu, Q.-M. 2001. New material of Mamenchisaurus hochuanensis from Zigong, Sichuan. Vertebrata PalAsiatica 39(4):266-271.
March 23, 2010
For various arcane reasons, the SV-POW!sketeers are all neck-deep in work, so the blog may actually become somewhat more of the APOD-style picture-n-paragraph thing we originally envisioned, and less of the TetZoo-style monograph-of-the-week thing it’s often leaned toward, at least for a while.
I like it when people decorate their papers with megapixels of vertebral goodness, so here are some caudal vertebrae of the African diplodocine Tornieria, from Remes (2006:fig. 5). Click through to see the figure at its massive native resolution. And check out that pneumaticity! Really, the only question about this image is whether you can settle for just using it as your desktop background, or if you need to print out a wall-sized poster for your bedroom. So the next time you see Kristian Remes, buy him a beer for doing solid work here, on the Humbolt sauropod remount, and on pretty much everything else (including this).
Remes, K. 2006. Revision of the Tendaguru sauropod Tornieria africana (Fraas) and its relevance for sauropod paleobiogeography. Journal of Vertebrate Paleontology 26 (3): 651–669.
October 13, 2009
UPDATE December 3, 2009
I screwed up, seriously. Tony Thulborn writes in a comment below to correct several gross errors I made in the original post. He’s right on every count. I have no defense, and I am terribly sorry, both to Tony and to everyone who ever has or ever will read this post.
He is correct that the paper in question (Thulborn et al 1994) does discuss track length, not diameter, so my ranting about that below is not just immoderate, it’s completely undeserved. I don’t know what I was thinking. I did reread the paper before I wrote the post, but I got the two switched in my mind, and I assigned blame where none existed. In particular, it was grossly unfair of me to tar Tony’s careful work with the same brush I used to lament the confused hodgepodge of measurements reported in the media (not by scientists) for the Plagne tracks.
I am also sorry that I criticized the 1994 paper and implied that the work was incomplete. I was way out of line.
I regard this post as the most serious mistake in my professional career. I want very badly to somehow unmake it. I am adding corrections to the post below and striking out but not erasing my mistakes; they will stand as a reminder of my fallibility and a warning against being so high-handed and unfair in the future.
I’m sorry. I beg forgiveness from Tony, from all of our readers, and from the broader vertebrate paleontology community. Please forgive me.
You might have seen a story last week about some huge sauropod tracks discovered in Upper Jurassic deposits from the Jura plateau in France, near the town of Plagne. According to the news reports, the tracks are the largest ever discovered. Well, let’s see.
The Guardian (from which I stole the image above) says the prints are “up to 2 metres (6ft 6 in) in diameter”, but ScienceDaily says “up to 1.5 m in total diameter”. Not sure how ‘total diameter’ is different from regular diameter, but that’s science reporting for you. The BBC clarifies that, “the depressions are about 1.5m (4.9ft) wide”, which might be the key here (see below), but then mysteriously continues, “corresponding to animals that were more than 25m long and weighed about 30 tonnes.” I find it rather unlikely that a pes track 1.5 m wide indicates an animal only as big as Giraffatitan (hence this post).
So there’s some uncertainty with respect to the diameter of the tracks–half a meter of uncertainty, to be precise. But sauropod pes tracks are usually longer than wide, and a print 1.5 m wide might actually be 2 m long.
Not incidentally, Thulborn (1994) described some big sauropod tracks from the Broome Sandstone in Australia, with pes prints up to 1.5 m. Although the photos of the tracks are not as clear as one might wish, they do appear to show digit impressions and are probably not underprints. [See Tony Thulborn's comment below regarding footprints vs underprints.]
I’ll feel a lot better about the Plagne tracks when the confusion about their dimensions is cleared up and when some evidence is presented that they also are not underprints. In any case, the only dimension with any orientation cited for the Plagne tracks is the 1.5 m width reported by the BBC, so we’ll go with that. So the Plagne tracks might only tie, but not beat, Thulborn’s tracks.
…Then again, Thulborn only said that the biggest tracks were up to 150 cm in diameter. What does that mean–length? Width? Are the tracks perfect circles? Does no one who works on giant sauropod tracks know how to report measurements? These questions will have to wait, because despite the passing of a decade and a half, the world’s (possibly second-) biggest footprints–from anything! ever!–have not yet merited a follow-up paper. [Absolutely wrong and unfair; please see the apology at top and Tony Thulborn's comment below.]
Nevertheless, for the remainder of this post we’ll accept that at least some sauropods were leaving pes prints a meter and a half wide. Naturally, it occurs to me to wonder how big those sauropods were. I don’t know of any studies that attempt to rigorously estimate the size of a sauropod from its tracks or vice versa, so in the finest tradition of the internet in general and blogging in particular, I’m going to wing it.
First we need some actual measurements of sauropod feet. When Mike and I were in Berlin last fall (gosh, almost a year ago!), we measured the feet (pedes) of the mounted Giraffatitan and Diplodocus for this very purpose. The Diplodocus feet were both 59 cm wide, and the Giraffatitan feet were 68 and 73 cm wide. The Diplodocus feet are trustworthy, the Giraffatitan bits less so. Unfortunately, the pes is the second part of the skeleton of Giraffatitan that is less well known than I would like (after the cervico-dorsal neural spines). The reconstructed feet look believable, but “believability” is hard to calibrate and probably a poor predictor of reality when working with sauropods.
One thing I won’t go into is that Giraffatitan (HM SII) probably massed more than twice what Diplodocus (CM 84/94) did, but on the other hand G. bore more of its weight on its forelimbs. It would be interesting to calculate whether the shifted center of mass would be enough to even out the pressure exerted by the hindfeet of the two animals; Don Henderson may have done this already.
Anyway, let’s say for the sake of argument that the hindfeet of the mounted Giraffatitan are sized about right. The next problem is figuring out how much soft tissue surrounded the bones. In other words, how much wider was the fleshy foot–deformed under load!–than the articulated pes skeleton? I am of two minds on this. On one hand, sauropods probaby had a big heel pad like that of elephants, and it seems reasonable that the heel pad plus the normal skin, fat, and muscle might have expanded the fleshy foot considerably beyond the edges of the bones. On the other hand, the pedal skeleton is widest across the distal ends of the phalanges, and in well-preserved tracks like the one below the fleshy foot is clearly not much wider than that (thanks, Brian, for the photo!).
Bear in mind that a liberal estimate of soft tissue will give a conservative estimate of the animal’s size, and vice versa. Looking at the AMNH track pictured above, it seems that the width added by soft tissue could possibly be as little as 5% of the width of the pes skeleton. Skewing hard in the opposite direction, an additional 20% or more does not seem unreasonable for other animals (keep in mind this would only be 10% on either side of the foot). Using those numbers, Diplodocus (CM 84/94) would have left tracks as narrow as 62 cm or as wide as 71 cm. For Giraffatitan (HM SII) I’ll use the wider of the two pes measurements, because the foot is expected to deform under load and the 73 cm wide foot looked just as believable as the 68 cm foot (for whatever that’s worth). Applying the same scale factors (1.05 and 1.20) yields a pes track width of 77-88 cm.
These numbers are like pieces of legislation, or sausages: the results are more pleasant to contemplate than the process that produced them. They’re ugly, and possibly wrong. But they give us someplace to start from in considering the possible sizes of the biggest sauropod trackmakers. Something with a hindfoot track 1.5 meters wide would be, using these numbers, conservatively more than twice as big as (2.11x) the mounted Carnegie Diplodocus or 170% the size of the mounted Berlin Giraffatitan. That’s right into Amphicoelias fragillimus/Bruhathkayosaurus territory. The diplo-Diplodocus would have been 150 feet long, and even assuming a very conservative 10 tons for Vanilla Dippy (14,000L x 0.7 kg/L = 9800 kg), would have had a mass of 94 metric tons (104 short tons). The monster Giraffatitan-like critter would have been “only” 130 feet long, but with a 14.5 meter neck and a mass of 113 metric tons (125 short tons; starting from a conservative 23 metric tons for HM SII).
Keep in mind that these are conservative estimates, for both the size of the trackmakers and the masses of the “known” critters. If we use the conservative soft tissue/liberal animal size numbers, the makers of the 1.5 meter tracks were 2.4 times as big as the mounted Diplodocus or almost twice as big as the mounted Giraffatitan, in which case masses in the blue whale range of 150-200 tons become not just probable but inevitable.
Going the other way, I can think of only a handful of ways that the “conservative” trackmaker estimates might still be too big:
First, the pes of Giraffatitan might have been bigger than reconstructed in the mounted skeleton. Looking at the photo above, I can image a pes 10% wider that wouldn’t do any violence to the “believability” of the mount. That would make the estimated track of HM SII 10% wider and the estimated size of the HM-SII-on-steroids correspondingly smaller. But that wouldn’t affect the scaled up Diplodocus estimate, and the feet of Giraffatitan would have to be a LOT bigger than reconstructed to avoid the reality of an animal at least half again as big as HM SII.
Second, the amount of soft tissue might have been greater than even the liberal soft tissue/conservative size estimate allows. But I think that piling on 20% more soft tissue than bone is already beyond what most well-preserved tracks would justify, so I’m not worried on that score. (What scares me more is the thought that the conservative estimates are too conservative, and the real trackmakers even bigger.)
Third, I suppose it is possible that sauropod feet scaled allometrically with size and that big sauropods left disproportionately big tracks. I’m also not worried about this. For one thing, when they’ve been measured sauropod appendicular elements tend to scale isometrically, and it would be weird if feet were the undiscovered exception. For another, the allometric oversizing of the feet would have to be pronounced to make much of a dent in the estimated size of the trackmakers. I find the idea of 100-ton sauropods more palatable than the idea of 70-ton sauropods with clown shoes.
Fourth, the meta-point, what if the Broome and Plagne tracks are underprints? [Please see Tony Thulborn's comment below regarding footprints and underprints.] I’ve seen some tracks-with-undertracks where the magnification of the apparent track size in the undertracks was just staggering. The Broom tracks have gotten one brief note and The Plagne tracks have not been formally described at all, so all of this noodling around about trackmaker size could go right out the window. Mind you, I don’t have any evidence that the either set are underprints, and at least for the Broome tracks the evidence seems to go the other way, I’m just trying to cover all possible bases.
So. Sauropods got big. As usual, we can’t tell exactly how big. Any one individual can leave many tracks but only one skeleton, so we might expect the track record to sample the gigapods more effectively than the skeletal record. Interestingly, the largest fragmentary skeletal remains (i.e., Amphicoelias and Bruhathkayosaurus, assuming they’re legit) and the largest tracks (i.e., Plagne and Broome) point to animals of roughly the same size.
It’s also weird that some of the biggest contenders in both categories have been so little published. I mean, if I had access to Bruhathkayosaurus or a track 1.5 m wide, you can bet that I’d be dropping everything else like a bad habit until I had the gigapod evidence properly written up. What gives? [The implication that the Broome tracks were not properly written up is both wrong and unfair; please see the apology at top.]
Finally, IF the biggest fragmentary gigapods and the biggest tracks are faithful indicators of body size, they suggest that gigapods were broadly distributed in space and time (and probably phylogeny). I wonder if these were representatives of giga-taxa, or just extremely large individuals of otherwise vanilla sauropods. Your thoughts are welcome.
Epilogue: What About Breviparopus?
It’s past time someone set the record straight about damn Breviparopus. The oft-quoted track length of 115 cm is (A) much smaller than either the Broome or Plagne tracks, and (B) the combined length of the manus and pes prints together; I know, I looked it up (Dutuit and Ouazzou 1980). Why anyone would report track “length” that way is beyond me, but what is more mysterious is why anyone was taken in by it, since the width of 50 cm (pathetic!) is usually quoted along with the 115 cm “length”, indicating an animal smaller than Vanilla Diplodocus (track length is much more likely than width to get distorted by foot motions during locomotion) [This part is wrong; see the update below.]. But people keep stumbling on crap (thanks, Guiness book!) about how at 157 feet long (determined how, exactly?) Breviparopus was possibly the largest critter to walk the planet. Puh-leeze. If there’s one fact that everyone ought to know about Breviparopus, it’s that it was smaller than the big mounted sauropods at museums worldwide. The only thing super-sized about it is the cloud of ignorance, confusion, and hype that clings to the name like cheap perfume. Here’s the Wikipedia article if you want to do some much-needed revising.
UPDATE (Nov 17 2009): The width of the Breviparopus pes tracks is 90 cm, not 50 cm. The story of the 50 cm number is typically convoluted. Many thanks to Nima Sassani for doing the detective work. Rather than steal his thunder, I’ll point you to his explanation here. Point A above is still valid: Breviparopus was dinky compared to the Broome and Plagne trackmakers.
You know I ain’t gonna raise the specter of a beast 1.7 times the size of HM SII without throwing in a photoshopped giant cervical. So here you go: me with C8 of Giraffatitan blown up to 170% (the vert, not me). Compare to unmodified original here.
- Dutuit, J.M., and A. Ouazzou. 1980. Découverte d’une piste de Dinosaure sauropode sur le site d’empreintes de Demnat (Haut-Atlas marocain). Mémoires de la Société Géologique de France, Nouvelle Série 139:95-102.
- Thulborn, R.A., T.Hamley and P.Foulkes. 1994. Preliminary report on sauropod dinosaur tracks in the Broome Sandstone (Lower Cretaceous) of Western Australia. Gaia 10:85-96.
After a completely barren 2008, this year is turning out to be a good one for me in terms of publications. Today sees the publication of Taylor (2009b), entitled Electronic publication of nomenclatural acts is inevitable, and will be accepted by the taxonomic community with or without the endorsement of the code — one of those papers where, if you’ve read the title, you can skip the rest of the paper. (Although on that score, my effort is knocked into a cocked hat by Hulke 1880.)
The message of the paper will be familiar to anyone who’s been following the Shiny Digital Future thread on this site; as indeed will parts of the text, as the paper is basically a more carefully worked and cohesive form of an argument that I’d previously spread across half a dozen blog posts, a similar number of emails on the ICZN mailing list and any number of comments on other people’s blogs. The sequence of section headings in the paper tells its own story:
And that conclusion reads as follows:
While we were looking the other way, the digital revolution has happened: everyone but the ICZN now accepts electronic publication. The Code is aﬀorded legitimacy by workers and journals only because it serves them; if we allow it to become anachronistic then they will desert it – or, at best, pick and choose, following only those provisions of the Code that suit them. Facing this reality, the Code has no realistic option but to change – to recognise electronic publishing as valid.
I have no detailed recommendations to make regarding the recently proposed amendments to the Code (ICZN, 2008). Instead I ask only this simple question: will the Code step up to the plate and regulate electronic publications as well as printed publications? Because this is the only question that remains open. Simply rejecting electronic publication is no longer a valid option.
Which I’m sure is familiar rhetoric to long-time SDF advocates, but which I hope will rattle a few cages in the more conservative ranks of specialist taxonomists. I think it’s a very promising sign that BZN, the official journal of the ICZN, is prepared to publish this kind of advocacy — they didn’t even ask me to tone down the language. I hope it indicates that in high places, they are sensing which way the wind is blowing.
Here’s a reminder of why electronic publishing is so desirable: figure 3 from Sereno et al.’s (2007) paper on the bizarre skull of the rebbachisaurid Nigersaurus:
Let me remind you that this was a paper about skulls — vertebrae were not even on the agenda. Yet click through the image (go on, you have to) and you will see them each presented in glorious high-resolution detail. That paper was of course published in the PLoS ONE — a journal that, because it is online only, can provide this quality of figure reproduction, which shames even the very best of printed journals. To see printed-on-paper figures this detailed and informative, you have to right back to Osborn and Mook (1921).
Which is why I recently decided to put my open-access money where my electronic-only mouth is, and submit the forthcoming Archbishop description to a PLoS journal. In response to a challenge from Andy Farke, I rather precipitately made a public commitment to do my level best to get that paper submitted this calendar year; and while that may not actually happen, having that goal out there can only help. Seeing that gorgeous quarry photo of Spinophorosaurus was what tipped me over the edge into wanting to use PLoS. My plan is to describe the living crap out of that bad boy, photograph every element from every direction and put the whole lot in the paper — make the paper as close as possible as a surrogate for the specimen itself. Only PLoS (to my knowledge) can do this.
(Of course, once you start wanting to include other kinds of information in your publications — videos, 3d models, etc. — then an electronic-only venue is literally your only option.)
I leave you with two photos of “Cervical P” of the Archbishop; commentary by Matt. These images are copyright the NHM since it’s their specimen.
- Hulke, J. W. 1880. Iguanodon Prestwichii, a new species from the Kimmeridge Clay, distinguished from I. Mantelli of the Wealden Formation in the S.E. of England and Isle of Wight by differences in the shape of the vertebral centra, by fewer than five sacral vertebrae, by the simpler character of its tooth-serrature, &c., founded on numerous fossil remains lately discovered at Cumnor, near Oxford. Quarterly Journal of the Geological Society 36:433-456. doi:10.1144/GSL.JGS.1880.036.01-04.36
- International Commission on Zoological Nomenclature. 2008. Proposed amendment of the International Code of Zoological Nomenclature to expand and refine methods of publication. Zootaxa 1908: 57-67, Bulletin of Zoological Nomenclature 65(4): 265-275 and various other places.
- Osborn, H. F. and C. C. Mook. 1921. Camarasaurus, Amphicoelias and other sauropods of Cope. Memoirs of the American Museum of Natural History, n.s. 3: 247-387, and plates LX-LXXXV. [HUGE download, but totally worth it.]
- Sereno, Paul C., Jeffrey A. Wilson, Lawrence M. Witmer, John A. Whitlock, Abdoulaye Maga, Oumarou Ide and Timothy A. Rowe. 2007. Structural Extremes in a Cretaceous Dinosaur. PLoS ONE 2 (11): e1230 (9 pages). doi:10.1371/journal.pone.0001230
- Taylor, Michael P. 2009. Electronic publication of nomenclatural acts is inevitable, and will be accepted by the taxonomic community with or without the endorsement of the Code. Bulletin of Zoological Nomenclature 66(3):205-214.
September 9, 2009
Today sees the publication of the new Journal of Vertebrate Paleontology, and with it my paper on the two best-known brachiosaurs and why they’re not congeneric (Taylor 2009). This of course is why I have been coyly referring to “Brachiosaurus” brancai in the last few months … I couldn’t bear to make the leap straight to saying Giraffatitan, a name that is going to take me a while to get used to.
But before we go lunging into the details, here is my skeletal reconstruction of Brachiosaurus proper, taken from the paper:
Those of you familiar with Greg Paul’s classic reconstruction of Giraffatitan brancai will immediately recognise that Real Brachiosaurus is rather differently proportioned, especially in having a longer torso and tail.
This paper has been in the works for some time, and while it was in review and then in press at JVP, it led a double life as Chapter 2 of my dissertation. (For most of its gestation period, the paper’s title was just “Brachiosaurus brancai is not Brachiosaurus“, and the folder where I keep all the project files is still called “bb-is-not-b”). In the end, I chickened out and went for a longer, more formal, title.
So why are the two species not congeneric? Well, it’s a long story, and you can read about the detail in the paper, but the bottom line is that virtually every bone that is known from both species differs in significant respects between them.
Of course, I am not the first to suggest that the African brachiosaurid that we know and love isn’t exactly Brachiosaurus. Credit for that goes to Greg Paul, who more than twenty years ago executed a then-new skeletal reconstruction of that species (the very same reconstruction that is now considered the classic), and in doing so noticed some differences between the American type species Brachiosaurus altithorax and the African referred species “Brachiosaurus” brancai (Paul 1988). Paul hedged his bets, though: rather than erect a new genus for the African animal, he proposed a subgenus Brachiosaurus (Giraffatitan), so that the full name of the species would become Brachiosaurus (Giraffatitan) brancai; and that of the type species would become Brachiosaurus (Brachiosaurus) altithorax. Unsurprisingly, this cumbersome nomenclatural scheme did not catch on, and I have not been able to locate a single subsequent reference to these subgenera in the literature.
That didn’t mean the idea was dead, though: three years later, George Olshevsky’s self-published mega-revision of dinosaur taxonomy proposed raising the name Giraffatitan to genus level (Olshevsky 1991). Although this genus became popular on the Internet (it cropped up, for example, in Mike Keesey’s much-lamented Dinosauricon web-site), it was almost completely ignored in the technical literature, and even Greg Paul himself subsequently seems to have reverted to using the name Brachiosaurus brancai (e.g. Paul 1994:246).
Why was the new name overlooked? Partly, I suspect, just because it’s so butt ugly — everyone knows and loves Brachiosaurus brancai, and the name itself has a definite poetry to it that Giraffatitan sorely lacks. But mostly it’s because Paul didn’t really make a case for the separation that he proposed — wrongly stating, for example, that “the caudals, scapula, coracoid, humerus, ilium, and femur of B. altithorax and B. brancai are very similar” (Paul 1988:7).
That’s how things stood a few years back when I started to take a serious interest in Migeod’s Tendaguru brachiosaurid, which lives in the basement of the Natural History Museum in London. It quickly started to seem to me that it wasn’t the same thing as what everyone means by Brachiosaurus, but to make sense of it all, I needed first to figure out what the Brachiosaurus actually does mean. That meant visiting the type material of both species, in Chicago and Berlin, and really looking closely.
Well, I don’t want to go on all day — apart from anything, England play Croatia in a World Cup qualifier in just over an hour — so I’ll just show you some of the the differences between the dorsal vertebrae of the two species. (You’ll have seen the caudals up above — I just threw them in to break up all that text).
Lots and lots of differences here — I will quote from the Systematic Paleontology section on the type species: “Postspinal lamina absent from dorsal vertebrae (character 130); distal ends of transverse processes of dorsal vertebrae transition smoothly onto dorsal surfaces of transverse processes (character 142); spinodiapophyseal and spinopostzygapophyseal laminae on middle and posterior dorsal vertebrae contact each other (character 146); posterior dorsal centra subcircular in cross-section (character 151); posterior dorsal neural spines progressively expand mediolaterally through most of their length (“petal” or “paddle” shaped) (character 155); mid-dorsals about one third longer than posterior dorsals (see Paul, 1988:7); middorsals only about 20% taller than posterior dorsals (see Paul, 1988:8); dorsal centra long (Janensch, 1950a:72) so that dorsal column is over twice humerus length (Paul, 1988:8); transverse processes of dorsal vertebrae oriented horizontally (Paul, 1988:8); dorsal neural spines oriented close to vertical in lateral view; dorsal neural spines triangular in lateral view, diminishing smoothly in anteroposterior width from wide base upwards; deep inverted triangular ligament rugosities on anterior and posterior faces of neural spines” …. *gasp*
So anyway: the upshot of all this is that “Brachiosaurus” brancai differs from Brachiosaurus altithorax more than, say, Barosaurus does from Diplodocus; and so it must be placed in its own genus … and that genus has to be Giraffatitan, because of the ICZN’s principle of priority. And THAT is why the very end of the paper — the last sentence of the Acknowledgements — reads:
Finally, I beg forgiveness from all brachiosaur lovers, that so beautiful an animal as “Brachiosaurus” brancai now has to be known by so inelegant a name as Giraffatitan.
Anyway, go and read the paper; full-resolution figures are freely available if you want to look more closely than the JVP’s PDF allows.
- Olshevsky, George. 1991. A Revision of the Parainfraclass Archosauria Cope, 1869, Excluding the Advanced Crocodylia. Mesozoic Meanderings #2 (1st printing): iv + 196 pp.
- Paul, Gregory 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.
- Paul, Gregory S. 1994. Dinosaur reproduction in the fast lane: implications for size, success and extinction. pp. 244–255 in: K. Carpenter, K. F. Hirsch, and J. R. Horner (eds.), Dinosaur Eggs and Babies. Cambridge University Press, Cambridge.
- Taylor, Michael P. 2009. A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from Giraffatitan brancai (Janensch 1914). Journal of Vertebrate Paleontology 29(3):787-806.
(And, yes, Randy, I know what your comment is going to say; go ahead and say it anyway, it’ll give me a chance to explain why your approach is wrong :-))
July 3, 2009
Big news today: Australia’s dinosaur fauna just got a little less depauperate. Hocknull et al. (2009) described three new saurischian dinosaurs in PLoS ONE, and two of them are sauropods! I’m just going to hit the highlights in this post. For all 51 pages of awesome, you can download the full paper for free.
Here are the new critters (Hocknull et al. 2009:fig. 40; oddly, the size of the scale bar is not given in the figure caption, but I assume it’s one meter). From top to bottom they are:
- Australovenator wintonensis, an allosauroid possibly close to Carcharodontosauridae;
- Wintonotitan wattsi, a basal titanosauriform;
- Diamantinasaurus matildae, a lithostrotian titanosaur.
The new taxa are from the late Early Cretaceous Winton Formation of eastern Australia. All three are represented by incomplete but diagnostic remains, and some of the material is really beautiful.
Here’s one of my favorite bits: the complete reconstructed manus of Diamantinasaurus (Hocknull et al. 2009:fig. 7). Sauropod forefeet were uniquely weird; for the full scoop read this. Note the thumb claw; if it’s legit–and the authors make a pretty good case that it is–then it’s unusual for a titanosaur, most of which are thought to lack hand claws and even manual phalanges.
Sadly no vertebrae were recovered with Diamantinasaurus, and those of Wintonotitan are not as pretty as the appendicular material. Still, they’re shards of excellence and they do carry some informative characters. Here are some dorsals and proximal caudals from Wintonotitan (Hocknull et al. 2009:fig. 13). You can see the partial rim of a pneumatic cavity on the dorsal in the upper left corner. According to the paper the sacrum was also pneumatic, which is to be expected in a titanosauriform.
There’s loads more to say about these critters and their implications for the evolution and biogeography of their respective clades, but tomorrow’s the 4th of July and I’ve got a barbeque to organize. Catch you on the flip side.
Hocknull SA, White MA, Tischler TR, Cook AG, Calleja ND, et al. (2009) New Mid-Cretaceous (Latest Albian) Dinosaurs from Winton, Queensland, Australia. PLoS ONE 4(7): e6190. doi:10.1371/journal.pone.0006190
May 20, 2009
Welcome to another episode of the ground-breaking and wonderful Sauropods of 2008 series. Yay! As I’m fond of pointing out, new dinosaurs do not only come from China, or South America: Europe continues to yield surprises. Tastavinsaurus sanzi Canudo et al., 2008 is from the Lower Cretaceous (Aptian) Xert Formation of Spain, and the holotype specimen is pretty good, including dorsal, sacral and caudal vertebrae, ribs, chevrons, and material from the pelvis and hindlimbs (we’ve previously mentioned it here, and figured some of it here). Evidently, only the hindquarters of the animal were preserved. But they’re in good shape, and preserve numerous unique characters: in fact 19 autapomorphies are identified, which is a pretty impressive number and indicates either that Tastavinsaurus was a highly disparate sauropod, or that the morphology of its close friends and relatives is but scrappily known (I have to say that the former possibility looks more likely).
Some of these autapomorphies are in the vertebrae. On the posterior surfaces of their neural spines, the antero-posteriorly short, opisthocoelous dorsal vertebrae sport two small accessory laminae that emerge from the base of a very wide, chunky looking postspinal process. Of more general interest (perhaps) is that the dorsal centra contain ‘big prismatic tubes linked together by slender walls [that exhibit] a honeycomb pattern in cross-section’ (Canudo et al. 2008, p. 713). The ‘honeycomb pattern’ sounds something like somphospondylous texture, but the authors note that the condition present in Tastavinsaurus is distinct, and perhaps represents a new type of pneumatic pattern. Frustratingly, they don’t illustrate the internal texture, so we’re left guessing.
The caudal vertebrae of Tastavinsaurus are not all that different from those of macronarians like Camarasaurus and Brachiosaurus: in the proximal caudals, the centra are wider than they are long, the proximal vertebrae have slightly procoelous centra, and the neural spines are ‘club-shaped’ [proximal caudal above from Canudo et al. (2008), fig. 7]. The more distal vertebrae – those from the 15th position onwards – are slightly amphicoelous. One weird little feature on the distal caudals is a small, centrally placed convexity on both the anterior and posterior articular faces of the centra (see pics below). As Canudo et al. (2008) note, Cedarosaurus and Pleurocoelus nanus both have this as well (Tidwell et al. 1999) [distal caudal below from Canudo et al. (2008), fig. 8].
The rest of Tastavinsaurus suggests that it would perhaps have superficially resembled a cross between Camarasaurus and Brachiosaurus. Its ilium looks like a dorsally stretched version of the ilium of Brachiosaurus and, indeed, in general character the specimen would appear to be a brachiosaur-grade titanosauriform. With pneumatic ribs, a lateral bulge on the femur, and caudal vertebrae that have anteriorly positioned neural arches, the rest of Tastavinsaurus agrees with this classification, and in their phylogenetic analysis, Canudo et al. (2008) found Tastavinsaurus to fall within Somphospondyli within Titanosauriformes, and within this clade to be the sister-taxon of Venenosaurus from Utah. If this is correct it weakens the proposal that six sacral vertebrae are a synapomorphy of Somphospondyli (Wilson & Sereno 1998), for Tastavinsaurus only has five.
Well, yet again I’ve done my best to concentrate on CAUDAL vertebrae, given that we have an obvious (and understandable) bias towards cervicals and dorsals. Someone has to speak up for tails. For previous instalments in the Sauropods of 2008 series please see the articles on Eomamenchisaurus, Dongyangosaurus, and Malarguesaurus.
Canudo, J. I., Royo-Torres, R. & Cuenca-Bescós, G. 2008. A new sauropod: Tastavinsaurus sanzi gen. et sp. nov. from the Early Cretaceous (Aptian) of Spain. Journal of Vertebrate Paleontology 28, 712-731.
Tidwell, V., Carpenter, K. & Brooks, W. 1999. New sauropod from the Lower Cretaceous of Utah, USA. Oryctos 2, 21-37.
Wilson, J. A. & Sereno, P. C. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Society of Vertebrate Paleontology Memoir 5, 68 pp.