Needless to say, one of the things I love most about Paco’s Brontomerus artwork is that it’s a rare and welcome example of the much neglected Sauropods Stomping Theropods school of palaeo-art.

When I reviewed the examples I know of, I was a bit disappointed to find that they number only five.  Here they are, in chronological order.

First, we have this gorgeous sketch by Mark Hallett, showing Jobaria (here credited as “unnamed camarasaurid”) quite literally stomping on Afrovenator:

To the best of my knowledge, this has never actually been published — I found it on Dave Hone’s Archosaur Musings, in the interview with Hallett.  Mark tells me that this was a concept sketch of possible main art for Paul Sereno’s North African dinosaur article, Africa’s Dinosaur Castaways in the June 1996 issue of National Geographic (Sereno 1996) — three years before Jobaria was described[1] (Sereno et al. 1999); but for some inexplicable reason, it wasn’t used.

It seems incredible to think that there was no published, or even completed but unpublished, sauropod-stomping-theropod art before the mid-1990s, but I’ve not yet found any.  I thought that Bakker might have come up with something in The Dinosaur Heresies (Bakker 1986) or The Bite of the Bronto (Bakker 1994); but I flipped through both and I don’t see anything relevant.  Anyone know of anything earlier?

The next entry on my list is Luis Rey’s striking Astrodon, carrying away a raptor that bit off more than it could chew.

This appeared in Tom Holtz’s outstanding encyclopedia (Holtz 2007), which I highly recommend for every interested layman, including but not limited to bright kids.  The image also turned up, with Luis’s permission, in the publicity for Xenoposeidon — notably in The Sun, one of Britain’s most downmarket, lowest-common-denominator tabloids, where it was a pleasant surprise indeed.

I just love the expression on the raptor’s face.  He’s going HOLY CRAP!, and his buddies are all like, Hey, dude, c’mon, we were only playing!  But Astrodon‘s all, Nuh-uh, you started this, I’m going to finish it.

Next up, and a year, later, we have this moody just-going-about-my-business Camamasaurus, squishing theropod eggs, nests and babies in a casual sort of way, as though he’s saying “Well, you should have got out of my way”:

As it happens, this one was done for me, by Mark Witton.  It was intended as an illustration for a “Fossils Explained” article that I was going to do for Geology Today on the subject of (get ready for a big surprise): sauropods.  In fact, I am still going to do it.  But since it’s been two and a bit years since I got the go-ahead from the editor, I’m hardly in a position to complain that Mark gave the image to Dave Martill and Darren when they suddenly needed artwork to publicise the findings of their Moroccan expedition.  (Since then, the Mail seems to have re-used this picture pretty much every time they have a story about dinosaurs — even when that story is complete and utter crap.)

I don’t mind too much about this Witton original being whisked away from me, because shortly afterwards Mark went on to provide me with a much better piece — the beautifully wistful Diplodocus herd scene that we used in the publicity for our neck-posture paper.

And, amazingly, that brings us up to date.  The next relevant artwork that I know of was Paco’s glorious Brontomerus life restoration, which you’ve already read all about.  Just to vary things a bit, this is the second of the two renders — the one that wasn’t in the paper itself:

So is that the end of the story for now?  Happily, not quite.  Emily Willoughby produced this alternative Brontomerus restoration on the very day the paper came out!

I’m not going to claim that this is close to the quality of the other four pieces in this article, but you have to admire the speed of the work.  Emily wrote most of the initial Wikipedia entry for Brontomerus, and produced this picture to illustrate it.  At first when I saw this, I thought Emily had misunderstood the paper as indicating powerful retractors, so that the drawing had Brontomerus kicking backwards like a horse. But when I looked closely I realised it’s kicking outwards, thanks to the enlarged abductors. Neat.

A question and a challenge

I’d like to end this post with a question and a challenge.  First, the question: what other pieces of palaeoart have I missed that feature sauropods handing theropods their arses?  There have to be others — right?

And the challenge: I’d love it if those of you who are artists were to fix this terrible hole in the fabric of reality?  I’d love to see new and awesome art on the timeless theme of sauropods stomping theropods.  How about it?  If any of you have influence with the Art Evolved people, you might try seeing whether you can get them to join in the challenge.  It would be awesome to see a whole new crop of these pieces!


  • Bakker, Robert T.  1986.  The Dinosaur Heresies: New Theories Unlocking The Mystery of the Dinosaurs and Their Extinction.  Morrow, New York.  481 pages.
  • Bakker, Robert T.  1994.  The Bite of the Bronto.  Earth 3 (6): 26-35.
  • Holtz, Thomas R., Jr., and Luis V. Rey.  2007.  Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages. Random House, New York.  432 pages.
  • Sereno, Paul C.  1996.  Africa’s dinosaur castaways.  National Geographic 189(6):106-119.
  • Sereno, Paul C., Allison L. Beck, Didier. B. Dutheil, Hans C. E. Larsson, Gabrielle. H. Lyon, Bourahima Moussa, Rudyard W. Sadleir, Christian A. Sidor, David J. Varricchio, Gregory P. Wilson and Jeffrey A. Wilson.  1999.  Cretaceous Sauropods from the Sahara and the Uneven Rate of Skeletal Evolution Among Dinosaurs.  Science 282:1342-1347.


[1] If you want to call it that.

Back in 2005, I made this drawing of the scapula of what would become Brontomerus. By the time we actually got the manuscript together to submit, I completely forgot that it existed! Which is just as well–I like the color photos of the bones in the PDF better than line drawings. Also, I traced this from a photograph of the medial view of the scap that was also at a sort of wonky angle, so the ventral “step” in the scapular border is not apparent (see Taylor et al. 2011: fig. 8 to see what I’m talking about).

Still, good or not, this does illustrate the danger of letting projects drag on forever.

Anyone else have horror stories of completely forgetting about work you’d done? The comment field is open.

After a couple of relatively hardcore posts on ilial osteology, we though it would be good to look at something lighter this time.  If you’re interested in dinosaurs, or indeed alive, you will hardly have been able to avoid seeing Francisco Gascó’s glorious life restoration of Brontomerus.  Here it is again, in case you’ve been in a coma:

As well as being Figure 12 of the paper (Taylor et al. 2011), it’s popped up absolutely everywhere in media coverage: among many others, it was used by the BBC, Guardian, Telegraph and Independent in the UK; by USA Today, Fox News and National Geographic in the USA; by Spiegel in Germany; and by SVT (the state-funded national TV station) in Sweden.  There’s no question that this image contributed hugely to selling the paper to the secular media.  It’s probably responsible for 80% of all the coverage our work got, and I’m confident that it’s going to quickly become one of those images that everyone recognises, like the tyrannosaur/styracosaur fight on the cover of The Dinosaur Heresies and indeed Charles Knight’s classic swamp-bound Brontosaurus.

So it was a huge win for us, and it’s worth looking at how it came about.

Back in 2004, Matt gave a talk at the SVP annual meeting, entitled Skeletal pneumaticity in saurischian dinosaurs and its implications for mass estimates.  The material in this talk became a chapter in the Wilson and Curry Rogers edited volume of sauropod papers (Wedel 2005).  Some time in 2006, Matt heard about the Paleonturology competition, which is all about making palaeontology accessible for teenagers, especially in Spain: anyone who’d had a paper published in 2005 was invited to submit it, and the judges would choose the one that seemed most amenable to being rewritten in a compelling way for non-specialists.  Matt’s 2005 paper won the 2006 competition, and the rewritten version of that paper was translated into Spanish and published in a very nice booklet which I am pleased to have a copy of (Wedel 2007).  In 2007, Matt was invited to the Fundación Dinópolis in Teruel, Spain, to receive his award, launch the booklet, and act as a judge for the 2007 competition.

The relevance of all this now finally becomes apparent: while in Teruel, Matt met Francisco “Paco” Gascó, and looked through some of his portfolio of palaeo-art — including, for example, this rearing Camarasaurus:

So Matt had Paco in mind as a promising palaeo-artist.  Then towards the end of May 2008, when we were readying the Brontomerus paper for submission (not to Acta Palaontologica Polonica — to a different journal, which didn’t take it) I wrote to Matt saying:

I’m attaching a tentative skeletal reconstruction that I did.  […]  Now I’m thinking: should we approach a palaeoartist to see if we can get a life restoration done in time for the launch?  The eponymous thunder thighs hardly make an impact in the skeleton, after all.

And Matt quickly replied suggesting that Paco could be the person to do it.  He sent a few samples, including the Camarasaurus above, and I was sold.   A couple of days later, Matt suggested the idea to Paco, he was up for it, and so we were all systems go.

At that time, Paco (who is now getting towards the back end of his Ph.D) was a humble recent graduate, which was great because it meant that Matt and I got to boss him about — something that he accepted with enormous good grace as we went through a sequence of some 44 images on the way to the pair that we ended up with.

By this time, Matt and I had already realised that we wanted the artwork to show kicking.  So we started out by asking Paco to mock up three very rough sketches of how he thought a Brontomerus-kicking-a-predator scene might be composed.  Here is one of the three — pretty representative:

Although this scenario is pretty sweet, it’s not really what we wanted as it shows Brontomerus kicking backwards like a horse, rather than forwards like a footballer.  (That’s a soccer player, for those of you in the USA.)  So Matt offered this concept sketch:

(It’s well worth clicking through and seeing the details.)

It’s interesting to see how much of the final image was already in place even in that very early sketch: the basic pose of the adult sauropod, the juvenile behind, the theropod getting its arse kicked — even if at this stage it was a juvenile Acrocanthosaurus rather than a mature Utahraptor.

With this reference in the back of his mind, Paco started work on a 3D model of the sauropod that would be the core of the composition.  He was quickly able to show us a first draft that had all the pieces in place to look convincing at least as a generalised sauropod:

Already at this stage, I was pushing for the uniquely Brontomerus-like aspects of the anatomy to be made more apparent, so I sent back this modified and uglified version of the image to give a sense of where we wanted to be heading:

(You might want to open this image and the previous one in two tabs and switch back and forth between them.)

The purpose of the modified version, of course, was to show how high the ilium would sit on the torso and how it brings forward the anterior margin of the leg muscles.  We wanted the thigh to be much more thundrous!  This was part of a merciless campaign of anatomical criticism of many, many aspects of the in-progress restoration — for example, the cross-sectional shape of the neck, which at this point had a crest on top and flat sides.  (You’ll notice that in the final version, the neck has the distinctive subtriangular cross-section that is produced by the ventrolateral excursion of the cervical ribs in sauropods.)

While that stream of refinement was going on, Paca was starting to skin the model.  Here’s the first version we saw that had skin texture:

Seeing this was an exciting moment in the progress of the project.  It was the first time that the artwork started to look like actual art, and the sauropod to look like an actual sauropod.  We knew then that we were on the way to somewhere good.

That feeling intensified the first time Paco showed us the complete cast of our little drama: mother, baby, and evil raptor, all skinned and showing rather fetching stripes which survived in more or less this form through to the final version:

By this stage, most of the anatomical problems are getting ironed out: the flat-sided shape of the neck has gone, replaced by a broader and wrinklier ventral aspect; and the ilium was higher on the torso, with the shape of the dorsal margin more closely reflecting that of the Brontomerus holotype ilium.

Note the care that Paco took with the juvenile: it’s not just a scaled-down copy of the adult, but proportioned subtly differently in a way that reflects what we know of sauropod ontogeny: the limbs grow isometrically, but the neck is positively allometric, so that Baby Bronto’s neck is noticably shorter in proportion.  At this stage, the baby is too big — more than half Mama’s size, whereas the sizes of the elements from the Hotel Mesa quarry suggested that he should be closer to a third of her size.

At the same time that Paco was working on the details of the models, we were all still batting around composition ideas, trying to find the best way to put our three actors together.  This version of Paco’s was similar in concept to Matt’s earlier sketch, but different in a lot of details: the baby is running away rather than sheltering, the theropod is rather bigger than before, and has morphed from an acrocanthosaur to a raptor; and it’s upside-down in an attempt to show that it’s not in control of the situation:

I wasn’t convinced by this version, because the theropod seems to have been spun 180 degrees on the spot as well as kicked upside-down: I felt that he needed to be in a posture that more naturally emerges from having been facing Mama when he was kicked, so I ‘shopped Paco’s sketch into this version:

As well as turning the baby around (something that didn’t really help). I flipped the raptor and tried, clumsily, to convey that Mama had broken its neck.  Of course, that didn’t really work, because the extension at the base of the neck is habitual for most tetrapods anyway, but it at least gave us a sense of the direction we wanted to go in.

OK, so back to the model.  Paco had sent us a simple lateral-view render of Mama alone, as well as the group shown above, so that we could more easily critique its anatomy in isolation.  Here is that simple render, followed by the vandalism I did on it to show changes that we still wanted.  (See what I mean about Paco being patient?)

As you can see  (and as you’ll see more clearly if you flip back and forth between the two images), I was asking for two changes.  The simpler was that I wanted to see the distinctive profile of the Brontomerus scapula showing through the skin.  The more interesting is in the profile of the tail.  It’s been shown in many sauropods that there is a distinctive upwards kink at the base of the tail, so that the dorsal profile of the body does not progress smoothly from hips to tail, and I wanted to see that in Brontomerus.  At the same time, the tail needed to have more flesh on it and the ischium should have been producing a visible bulge in the ventral margin behind the hips.

The next version addressed these points (though the scapula outline was not yet right):

But picky as I am I still wasn’t satisfied…

I made a few changes here — again, in a hacky way using the GIMP, with the result not in any way intended as in improvement in itself, but as a sketch of how the model could be improved.  I shifted the tail up a little, smoothed the dorsal profile so that there was no longer a sort of dip at the base of the tail, and smoothed out the rear margin of the top of the thigh, so that there was no longer a “buttock”, but a hint of caudofemoralis musculature connecting the tail-base with the thigh.

Once Paco had made the necessary changes to the model, the next render looked superb — and very recognisable as the basis of the now-ubiquitous final version:

At this point, work on the main model was essentially complete, and Matt and I were both really happy with the result.  For people who’ve spent as much time gazing at the Brontomerus ilium and scapula as we have, this is very obviously Brontomerus and not just a generic sauropod.  Now it was time to put the model together with the composition ideas we’d been playing with:

We went through several versions of this, mostly varying in the posture of the theropod, but this is the one that led to the final piece.  For the first time, we were all happy with Baby Bronto in this one, too: he’s about the right size, and has a sort of skittering look to him, as though he wants to be elsewhere but doesn’t want to leave Mama.  (Am I anthopomorphising?  Very well; I contain multitudes.)  It’s a bit too close to the adult, though, so we can’t quite see its shape.  This was fixed in the next version, which also contained a backdrop for the first time:

Now we’re really getting somewhere.  You’ll notice that the raptor’s head is bent further back this time, hopefully conveying that its neck is broken.  But because I was really keen on getting it across that the raptor is DOWN and it’s NOT getting up again, I once again vandalised Paco’s work, this time with buckets of blood:

What I wanted to convey was: if this raptor wasn’t already secondarily flightless, it is now.  Still, I admit that the amount of blood, and the vividness of its colour, are a little over the top.  So in the final version, Paco took some of the blood back out, and toned it down to a more realistic colour.  The other important difference is that the raptor was moved a bit closer to the sauropod — not because that’s necessarily a better composition, but because we expected newspapers and other media outlets to crop the image mercilessly, and we wanted to give them best chance of keeping all the key element in frame when they did.

And so we arrive at the final version, as it appeared in the paper:

The very last thing we did was ask Paco for a second render of the same scene, so that media outlets would have a choice of artwork and wouldn’t all need to use the exact same image.  That was doable because all three dinosaurs, with their skin-textures, were built as a 3D model, which can be viewed from any angle.  But producing a finished artwork from this is not trivial: once an angle is chosen and the animals rendered, there is still a lot of post-production work to be done in putting in the background, the blood, the dust and so on.  So we didn’t ask for a complete array of 128 of these — just the one addition.  After reviewing a few candidate exported renders, we settled on one from a more anterolateral perspective, and Paco worked his magic to yield this alternative take:

I hardly have words to tell you how much I love this.  Several times, looking at it, I’ve found myself laughing out loud at how comprehensively the theropod is getting owned.  It’s OVER for that would-be predator.  It’s DONE.  The only question is whether Mama is going to put it out of its misery by stomping it flat, or whether it’ll be left to bleed out.  Either way, it picked on the wrong victim for dinner.

Part of what I love so much about this is that Brontomerus looks like an animal, not like a monster.  It works anatomically, feels like something that lives and breathes … and, indeed, kicks.

Let me close by clearly stating that 99% of all the Awesome here is the work of Paco — a talented and hardworking guy, who made Matt’s vision come to life.  My own input was basically restricted to whining.  I hope we’ll be seeing this image for many years to come, and that plenty more of Paco’s pieces make it out into the wide world where they belong.

For more of Paco’s stuff, please see his blog, El Pakozoico (TARDIS alert!), and his deviantART page.


Let’s look a bit more closely at the holotype element of Brontomerus mcintoshi, which as we all remember is the juvenile left ilium OMNH 66430.  Much of what we’ve said about Brontomerus is based on the shape of that ilium, so it’s important to get right.  Several commentators have expressed skepticism about how we reconstructed, so I thought it would be worth taking the time to explain why we put it together we way we did.

First, let’s orient ourselves.  Here is the torso from the skeletal inventory that was Figure 1 of the paper (Taylor et al. 2011, natch).  In this version, I’ve highlighted the ilium in red.  We’re looking at the left side of the animal, so the main part of the bone is further forward than the hip socket, towards the animal’s head.

As you’ll see from the area that we left shaded grey, a chunk is missing from the middle of the ilium, where it was damaged in the field.  As the figure of the ilium in the paper shows clearly, what we actually saw in the OMNH collection was three chunks of bone: a big one consisting of the acetacular margin, pubic and ischiadic peduncles and most of the preacetabular blade; and two smaller fragments, each contributing part of the dorsal or posterior margin.

We spent a while in the OMNH collection playing with the three chunks to see how they best fit together.  In doing this with the actual bones, we were able to take account of their curvature in the third dimension, which our figure don’t show — although a dorsal-view photo gives some idea.

Anyway, we this is what we came up with:

(Sorry if that image is getting a bit overfamiliar, but it’s worth seeing again in the context of this post.)

You’ll remember from the Clearing the Air post that Jim Kirkland, who excavated the ilium, felt that we’d got the two smaller fragments in the wrong places relative to the main chunk, and also that a fourth fragment which we’d missed also belongs to the ilium.  He kindly sent a photo of how he’d reconstructed the ilium, and I used the arrangement of pieces in the photo as the basis for a “what if” alternative reconstruction.

So far, this is old news.  But what was maybe not quite clear in the post is how very similar the two reconstructions really are.  Let’s fix that: here they are side by side, with ours on the left and Jim’s on the right:

It seems pretty clear that even if Jim’s arrangement is correct (which Rich Cifelli  disputes), that doesn’t affect the reconstruction in any significant way.

But the real question is why we put in that dotted line — and why we put it where we did.  How do we know there wasn’t a normal-sized postacetabular lobe sticking out behind?  This is what Jamie Headden wanted to know in an email to me shortly after the paper come out.  With his kind permission, I reproduce the illustration that he prepared, showing (A) the reconstruction from the paper, and (B) how it might have been different:

The reason we rejected a reconstruction like the one in Jaime’s part B is explained (too) briefly in the paper (pp. 80-81):

The postacetabular lobe is reduced almost to the point of absence […]  The ischiadic peduncle is reduced to a very low ventral projection from almost the most posterior point of the ilium. The near absence of the ischiadic peduncle cannot be attributed to damage as the iliac articular surface is preserved. Immediately posterodorsal to this surface is a subtle notch between the peduncle and the very reduced postacetabular lobe. This notch and the areas either side of it are composed of finished bone, demonstrating that the great reduction of the postacetabular lobe, too, is a genuine osteological feature and not due to damage.

To my lasting annoyance, I didn’t take any posterior-view photos of the ilium back in 2007, so I can’t show you this finished bone as well as I’d like — this was back before I’d learned all my lessons on how to photograph bones.  But here is a close-up of the posterovental extremity of the ilium, again from Fig. 2, showing the notch: I have left the postacetacular lobe in colour, and desaturated the ischiadic peduncle — the notch is between them.

This next photograph of the ilium, again in lateral view, is lit rather differently from the one we used in the figure, so that you can see a distinct shadow lying along the valley between the ischiadic peduncle and what there is of the postacetabular blade.

Here’s one that shows the main chunk of the ilium in anteromedial view: from here, you can more easily see the the distinction between the ischial peduncle (which projects towards the camera) and the preserved, ventralmost, part of postacetacular blade, which is further back.

And one in posteroventral view: this is similar to our Fig. 2b, but from a slightly more posterior (and medial) perspective, so that you can more easily see the mediolaterally compressed posterior lobe sticking out behind the broader ischial peduncle at top right:

What all these photos unfortunately do not show is the finished nature of the bone on the posterior margin of the postacetacular blade — on that, you just have to take our word.

But the point is this: we have the whole of the ischiadic peduncle and the ventralmost part of the postacetacular blade — we know that the posteriormost preserved part of the main chunk of ilium is not part of the peduncle (so that the postacetabular blade is missing), but that this really is the blade itself.  And because the bone is not broken, we know that the trajectory of the posterior margin of the postacetabular blade was directed dorsally from the posterior point of the peduncle.

I hope that’s clear.  What I really should have done, of course, was take my own good advice and get photos from every angle — and, ideally, pairs that would have allowed me to show the relevant features as anaglyphs.

Anyway, all this shows that the shape of the ilium really was pretty much as we reconstructed it — and, most, importantly, that the bizarre proportions we reported in Table 4 are correct: preacetabular blade, measured parallel to the longest axis of the ilium equal to 55% of total length; postacetabular blade equal to 0%.

Exactly how strange is this almost non-existent postacetabular blade?  In the paper we described it as “remarkable”, but it’s not completely unprecedented.  Lehman and Coulson (2002:fig. 8) showed the left ilia of six somphospondylians:

As you can see, the Euhelopus zdanskyi and Saltasaurus loricatus ilia both lack postacetabular blades (although Powell 1992:fig. 18 suggests that the posterior portion of the Saltasaurus ilium may be broken).  Where Brontomerus is unique is in the combination of this postacetabular reduction with the enormous preacetabular blade.

All clear?  Good.

“But wait!”, I hear you cry.  “That ilium is juvenile!  How do you know that its strange shape is not a juvenile feature?”

Stay tuned!  All will be revealed.


Sorry for the very short post. We have some longer stuff planned, but we’ve been too busy to kick it out this week, and I wanted to leave you with something cool to ponder over the weekend. Here’s the ilium of Giraffatitan overlaid on that of Brontomerus, scaled to the same acetabulum diameter (Giraffatitan is HMN J1, left ilium, modified from Janensch 1961: pl. E, fig. 2; Brontomerus is of course OMNH 66430 from Taylor et al. 2011:fig. 2).

And here’s the same thing comparing Rapetosaurus and Brontomerus (Rapetosaurus is holotype FMNH PR 2209, left ilium, modified from Curry Rogers 2009: fig. 39B). This one was tricky to scale because the ilial margin of the acetabulum is so different in the two taxa.

Here is the same trick performed with the ilium of the canonical pretty basal neosauropod Camarasaurus — specifically, Camarasaurus supremus AMNH 5761 Il. 1, left ilium, modified from Osborn and Mook (1921: fig. 87).  In this case, the proportions are so very different that it’s hard to make a meaningful superimposition: we tried to scale to equal acetabulum size, but probably that of the Camarasaurus was proportionally larger than in the other taxa illustrated in this post.  Still, here it is:

Finally, in response to Paul Barrett’s comment on a subsequent article, here is a superimposition of the ilium of Alamosaurus on that of Brontomerus:

(Sorry about the poor quality of this one, but the only figure I could find of a complete Alamosaurus ilium was the line-drawing in Lehman and Coulson (2002:fig. 8) — none of the standard descriptive works seem to illustrate a complete or near-complete ilium.)

We had a figure like these in an early draft of the paper, but we ditched it because we felt that doing a broader comparative figure would be more valuable. But I like the kick in the brainpan that these overlays provide.



Many people in the paleontological community have probably seen the comments about our work on Brontomerus by Jim Kirkland. Most of these comments have been posted on Facebook or sent around by email. We have held off until now in responding to them because we wanted to have everything–both the criticisms and our responses–publicly available to everyone, not in the walled garden of Facebook. Jim has now stated on Facebook that we have permission to post his messages and respond to them, and his longest critique has been posted as a comment on the initial Brontomerus post.

All three of us–Mike, Matt, and Rich, the authors of the new paper describing Brontomerus–have known Jim for some time. He and Rich collaborated in the Cedar Mountain Formation for most of the 1990s, and basically split the catch, with Jim getting most of the dinosaurs and Rich getting the mammals. Matt has known Jim since the late 1990s, and has had many productive conversations with him about sauropods and faunal change in the Early Cretaceous of North America. Mike’s interactions with Jim have been more limited, mainly because they live on different continents, but he has spoken to Jim at meetings and they have exchanged occasional correspondence–always friendly–for years.

Not only has Jim been a friend of ours for some time, he also assisted with the Brontomerus project. Jim first alerted Rich to the existence of the quarry in 1994. Following Rich’s visit to the quarry in September of that year, Jim went out with Scott Madsen and Randy Nydam to collect the fossils of what would become Brontomerus in 1995, and the fossils were prepared under his guidance at Dinamation before being transported to the Oklahoma Museum of Natural History for curation. Jim was also helpful in providing information about the quarry and allowing us to cite personal communications from him in the paper.

We’ve all had long and productive working relationships with Jim for years, and we’d like to see those relationships continue. However, some of his comments are not only factually incorrect but also call our veracity and scientific judgment into question. We feel that the record should publicly be set straight.

In the rest of the post, we have the full text of Jim’s long SV-POW! comment and some of his comments from Facebook,  followed by a breakdown of his specific claims and our responses to them.

Jim’s self-described rant

On February 23, Jim sent around an email with the subject “Brontomerus pdf and rant”. ReBecca recently posted a slightly longer version here on Jim’s behalf.

While, it is possible, that Brontomerus is a new species based solely on the juvenile ilium, there is no way based on the minimal contextual information known of this site, that one can say that all the sauropod material we collected at Hotel Mesa pertains to the same species.

When, I was first taken to this site in 1994, it had been opened by guys hoping to develop a commercial Morrison dinosaur quarry. The Bureau of Land Management (BLM) clearly did not OK this! Another party, who told me he had only advised them to get a permit, subsequently took me out to the site.

Examining this site, it was obviously in the Cedar Mt. Fm. [LINK] and of great interest to me, but politics being what they were, I could not get a BLM permit in Utah and as I had recognized a fair number of teeth and claws (theropods and crocs) in the site, I thought perhaps it might be a potential microvertebrate site, so I asked Rich Cifelli at the OMNH if he might be interested in the site. Rich put me on his Utah BLM permit and sent out Randy Nydam and I corralled Scott Madsen (then at Dinosaur National Monument (DNM) and we went out to evaluate the site for microvertebrates and salvage the exposed bones. This took us about 1.5 days (camped for two nights). Unfortunately, the matrix would not break down and thus the site could not be screenwashed for microvertebrates, so Rich lost interest in the site. We prepared all the bones in our (Dinamation Intl. Soc.) lab in Fruita, Colorado before sending them on to the OMNH with his crew when they returned to Oklahoma from working their Utah sites at the end of the following summer.

After, I became Utah’s State Paleontologist in 1999, I expressed interest in reopening the Hotel Mesa Quarry, as this was the only Albian age site in all of eastern Utah, but BLM policy was that all specimens from a given site needed to be reposited at the same repository. Therefore, since Utah paid my salary, it was impossible to justify excavating and preparing a collection of vertebrate materials and sending them to Oklahoma.

A few years ago, Mike Taylor informed me that he and Matt Wedel felt that there was a new sauropod taxon in the collections from Hotel Mesa. I was excited to learn this, as I figured they would seek to open the site and collect more specimens and data concerning this important locality.

I was deeply saddened to learn they had described the new sauropod taxa with no regard to establishing a base of contextual data to support its hypodym.

First there is no evidence to suggest that all the sauropod bones in the site pertain to the same taxon. The Holotype ilium (cute as a bugs ear, I must say, particularly before the shim went through the middle of it, when we flipped the scapula jacket), comes from a much smaller animal that the rest of the reported “hypodym”.

The nearly equivalent and geographically much closer Price River 2 Quarry preserves more than one sauropod taxon among the many hundreds of sauropod bones collected there. Staff at CEUs Prehistoric Museum pointed out that they had long cervicals similar to Sauropossiden and short stouter cervicals. Their new director Ken Carpenter sent me this picture [LINK] showing two morphs of ilia (at top of figure), one with a short prepubic portion and a stout pubic peduncle and on with a long prepubis and slender pubic peduncle. Thus, the Upper Albian part of Cedar Mt preserves a wealth of sauropods and this taxon promises to add to the general confusion regarding North America’s Early Cretaceous sauropods.

Also in terms of stratigraphy (and these guys are not completely at fault here, but if asked I would have told them), the Ruby Ranch Member is Albian in age from all our dating. Abydosaurus mcintoshi from DNM is not from the younger Mussentichit Mbr. but the upper Albian (Chure et al.’s 2010, date of ~104 Ma says that) and as stated in … our abstract coming out at GSA this spring and to be submitted as a manuscript long before that, An unconformity (sequence boundary) separates the basal Cenomanian (98-96 Ma) Mussentuchit from the Albian strata below it. Two date, there are no over lapping parts between Brontomerus mcintoshi and Abydosaurus mcintoshi and these two sites may nearly be equivalent.

The much older upper Barremian to basal Aptian Dalton Wells Quarry low in the Cedar Mt has at least 3 sauropod taxa among the numerous individuals in Brigham Young University’s collection. Remember the Cedar Mountain represents about as much time as the entire Upper Cretaceous.

Basically, the statement that the juvenile holotype belongs to the same taxon as the handful of adult material in the site is a stretch without some supporting taphonomic documentation (more excavation, as the site keeps going. However, the statement is a falsifiable hypothesis so is a scientific statement that needs testing.

Now that we are beginning to excavate our own sauropods, which thank god are at the base of the Cedar Mt. Fm., I’m actually beginning to care about the general taxonomic mess that Albian sauropods are in with the number of taxa described without overlapping parts.

Another observation that I accidentally made was that the reconstruction of the ilium in the paper, differs from that we made in preparing the specimen fresh from the field. These two reconstructions are shown in at the bottom of the picture. We figure this reconstruction from 1995 in Kirkland and Madsen, 2007, Fig. 13E, p. 15). On line at: [LINK]

I’m certainly curious what happened between Rich’s OMNH crew’s picking the specimens up and Mike and Matt’s beginning their research on it. Regardless of whatever happened, it is clear the proportions on the Holotype ilium need to be reappraised.

PLEASE, someone open up this quarry and generate some real information (it is an 8hr drive from Salt Lake City, so I do not have the funds to undertake this). The site is in the Dolores Triangle so the Hotel Mesa Site can only be approached from Colorado, so the Museum of Western Colorado is by far the closest institution to it.

AND; finally, the site is actually in the Burro Canyon Formation not the Cedar Mountain Formation as the name changes as you cross the Colorado River going east. So the stratigraphic level would be, for the sake of accuracy by best referred to as high in the Ruby Ranch Member of the Burro Canyon Formation. This is how it is show on the recently published 1X100,000 geological map of the area. Geological jargon that is useless to argue with unless you are going to publish the justification of changing the convention.

Oh and there are many dozens of sauropods waiting to be excavated in the Ceadar Mountain Formation during the “Age of Ankylosaurs.”

Done spouting off for the minute.

Jim Kirkland

Jim’s Facebook comments

Besides the email/SV-POW! comment, Jim has posted some serious criticisms of the paper on Facebook. These started back in January, when the accepted manuscript of the as-yet-unpublished paper was inadvertently posted on the Acta site. Jim kindly took them down following our request that he do so. However, the deleted criticisms had already been seen by hundreds of people  (Jim has 898 Facebook friends) and received many comments, so we feel that it is appropriate to publicly respond to them.

[January 28] Since Abydosaurus mcintoshi and Brontomerus mcintoshi are essentially from the same stratigraphic horizon ~ 150 kilometers apart and have no overlapping parts yet. It is an interesting synonymy since the species name would not change. We have all these sauropod skeletons in the Cedar Mountain, lets not describe scrap.

[January 28] I have wanted to see the Hotel Mesa site (turned over to OMNH) excavated for more than a decade. To describe a dinosaur from scrap salvaged from site and to leave rest rotting in the ground is irresponsible!

[January 28] Jim Kirkland: WTF I oversaw the collection of it all, as salvage over a couple of daysl None of these guys have been to site (more there). No way, you can say anything, but the type illium goes to this species.
Darren Naish: Are you sure that none of the guys have been to the site? Err…Rich Cifelli?
Jim Kirkland: I guarantee it, they would never find it.

[February 23] I just realized that they reconstructed the ilium of Brontomeris wrong! See my Hotel Mesa album. It is not thunder thighs, but at most quivering thighs! I would say it throws a big hook into the entire thing.

[February 23] There is no evidence that anything was stolen from the site or smashed for that matter. They simply uncovered it and inquired about a commercial permit.[speaking here of the alleged vandalism of the site by commercial collectors]

Specific claims, and our responses

We’re rather baffled by some of Jim’s statements. Rather than go through the email and Facebook comments line by line or in chronological order, we’ve distilled his criticisms into a number of specific claims, which appear here with our responses.

Claim 1: None of the authors ever visited the quarry.

Source: Facebook, “None of these guys have been to site…I guarantee it, they would never find it.”

Response: This not just incorrect, but insulting. From the paper (Taylor et al. 2011: 76):

One of us (RLC), who had already been working in Lower Cretaceous rocks of the region, was notified about the site through the courtesy of James I. Kirkland, and was guided to it by Bill Hawes of Grand Junction, Colorado, in September 1994. Additional collecting at the site for OMNH was conducted by Randall L. Nydam and James I. Kirkland in March 1995.

In an email to Matt and Mike with permission to cite, Rich wrote:

I took the information directly from my field notes and I remember the place pretty well. Of course I was there!

Claim 2: We erred in describing the site as being part of the Cedar Mountain Formation rather than the Burro Canyon Formation.

Source: SV-POW! comment, “the site is actually in the Burro Canyon Formation not the Cedar Mountain Formation as the name changes as you cross the Colorado River going east. So basically the proper description of the site would say, it is in the upper part of the Ruby Ranch Mbr. of the Burro Canyon Formation.”

Response: We acknowledge this in the paper, and clearly state that our discussion of the site as part of the CMF is one of convenience (Taylor et al. 2011: 76):

Stratigraphically, OMNH V857 lies in a sequence of Lower Cretaceous rocks interposed between the Morrison Formation (Kimmeridgian) below and the Dakota Formation (Cenomanian) above. Westward, these rocks are recognized as the Cedar Mountain Formation; eastward, the Burro Canyon Formation. The arbitrary dividing line between these entities is generally placed at the Colorado River (Stokes 1952; Tschudy et al. 1984) which technically places OMNH V857 within the Burro Canyon Formation. However, we will refer to the locality as belonging to the more widely recognized Cedar Mountain Formation, as it is in this formation that comparable specimens are known, and the stratigraphy and sedimentology do not change across the arbitrary border.

It is also worth noting that in his long comment, Jim himself discusses the quarry as part of the Cedar Mountain Formation, presumably out of convenience: “Examining this site, it was obviously in the Cedar Mt. Fm.” (from the third paragraph of his SV-POW! comment).

Claim 3: The quarry probably has more than one sauropod taxon, because other CMF quarries sometimes have more than one sauropod taxon. (conflicts with Claim 8)

Source: SV-POW! comment, “First there is no evidence to suggest that all the sauropod bones in the site pertain to the same taxon. The Holotype ilium (cute as a bugs ear, I must say, particularly before the shim went through the middle of it, when we flipped the scapula jacket), comes from a much smaller animal that the rest of the reported “hypodym”.

“The nearly equivalent and geographically much closer Price River 2 Quarry preserves more than one sauropod taxon among the many hundreds of sauropod bones collected there.”

Response: This is a possibility we discuss extensively in the paper (Taylor et al 2011: 79), but so far there is no evidence to support it. All of the material is consistent with a single taxon, most likely a basal somphospondyl, but conservatively a camarasauromorph.  (We plan to talk much more in a subsequent article about this tentative assignment of all the material to a single taxon.)

There is a more general point to be made here. Any time someone erects a new taxon, the idea that the taxon is actually distinct from other, previously named, taxa is a hypothesis subject to further testing. Anytime someone refers material to a taxon, that is likewise a hypothesis. If we pretended to be any more certain about the referral than we actually are, we’d be lying. But we’d be equally in error if we didn’t point out that the null hypothesis is that all of the material belongs to one taxon. If contrary evidence comes to light, we’ll take it into account and move on–that’s how science works.

If someone find a complete titanosaur skeleton with an ilium like the holotype of Brontomerus, and someone else turns up a complete rebbachisaur with a scapula like the one currently referred to Brontomerus, great!  Name the rebbachisaur (a North American rebbachisaur would rock!), remove the scapula from the Brontomerus Referred Material list, and move on.  As we made clear in the paper, Brontomerus is based on, and diagnosed by, the holotype ilium alone.

Claim 4: There is no evidence that anything was stolen or destroyed from the site.

Source: Facebook, “There is no evidence that anything was stolen from the site or smashed for that matter. They simply uncovered it and inquired about a commercial permit.” Also repeated second-hand as a comment on Dinosaur Tracking, here.

Response: In an email with permission to cite, Rich wrote:

Yes, of course it had been excavated: we have proof in my notes and in Randy Nydam’s field notes. The comments about bone strewn around and being used to hold pieces of blue tarp are, unfortunately, accurate.

What’s more puzzling is that all three of us have received emails from Jim going back to 2007 that clearly state that the quarry was vandalized.  For example (and note the explicit permission to cite):

Message-Id: <>
Date: Mon, 17 Mar 2008 10:22:12 -0600
From: James Kirkland
To: Mike Taylor
Subject: Re: Another Hotel Mesa pers. comm.

[…].  The small ilium was under the scapula (completely hidden and the shim went through the middle of it, but we were able to prepare it with it’s entire margin reconstructed.  (collected by Jim Kirkland, Scott Madsen, & Randy Nydam from site that had been uncovered previously by vandals).  […]

Site this.

Claim 5: The quarry is full of more and better sauropod material.

Source: Facebook, “To describe a dinosaur from scrap salvaged from site and to leave rest rotting in the ground is irresponsible!”

Response: Any material exposed near the surface at Hotel Mesa in 1994 and 1995 is long gone by now, crumbled by 16 years of freeze/thaw cycles and erosion by wind and water. There may be more material deeper down, a possibility that we have always acknowledged, but since no one has ever seen that material, it is impossible to say if it’s better than what we have, or if it even exists at all. This is actually not unusual for dinosaurs; many taxa are known from quarries that are not worked to exhaustion and later produce more material. One of our express aims in writing this paper was to to provide the impetus for further excavation in the quarry, and there was no prospect of that happening before we started working on it.

Claim 6: It was irresponsible of us to name a new dinosaur based on such incomplete material.

Source: Facebook, “We have all these sauropod skeletons in the Cedar Mountain, lets not describe scrap.”

Response: Although incomplete, the material still bears numerous autapomorphies that clearly indicate that it is a new taxon based on currently available data (see point 3, above, on hypotheses).

Since the material in the quarry was not articulated, we would have had to choose an isolated element as the holotype even if we had more material (and the ilium would still have been the obvious choice because it is so unusual). This is absolutely critical: in a bonebed of disarticulated elements, it wouldn’t matter if we had just the ilium or 5000 bones, we’d still have to pick one element as the holotype and refer everything else to it. Anyone describing a new taxon from disarticulated elements in a bonebed faces the same decision: for example, Kirkland et al. (2005), in their description of the basal therizinosaur Falcarius, nominated a partial braincase as the holotype and referred all the other material.

Claim 7: We erred in attributing Abydosaurus to the Mussentuchit member of the Cedar Mountain Formation.

Source: SV-POW! comment, “Abydosaurus mcintoshi from DNM is not from the younger Mussentichit Mbr. but the upper Albian (Chure et al.’s 2010, date of ~104 Ma says that) and as stated in … our abstract coming out at GSA this spring and to be submitted as a manuscript long before that,”

Facebook, “Abydosaurus mcintoshi and Brontomerus mcintoshi are essentially from the same stratigraphic horizon” [Brontomerus is from the Ruby Ranch member]

Response: The only published peer-reviewed work on the Abydosaurus quarry (Chure et al. 2010) places it in the Mussentuchit member. Jim’s abstract was not available to us when we were writing the paper, and if we had the option to choose between the conclusions of a peer-reviewed paper and those of an unpublished abstract, we’d still have followed the paper. Abydosaurus could actually be from the Ruby Ranch member, but we will wait for the published evidence, and to see what Chure et al. have to say in response.

Claim 8: Because Abydosaurus is from the Ruby Ranch member, Brontomerus might simply be Abydosaurus. (conflicts with Claim 3)

Source: Facebook, “Abydosaurus mcintoshi and Brontomerus mcintoshi are essentially from the same stratigraphic horizon ~ 150 kilometers apart and have no overlapping parts yet. It is an interesting synonymy”

Response: The hypothesis that Abydosaurus is from the Ruby Ranch member is far from convincingly demonstrated (see above). The Ruby Ranch member has at least two sauropods other than Brontomerus, and the Yellow Cat member has between three and five, so the idea that there is only one sauropod genus in each member of the CMF, and that therefore Brontomerus must be synonymous with Abydosaurus, is insupportable. Potential synonymies among Early Cretaceous North American sauropods are acknowledged and discussed extensively in the paper (Taylor et al. 2011: 87-88, 91-92).

Also, we note that back in January, Jim was concerned that Brontomerus was synonymous with Abydosaurus (not enough new sauropods in the quarry), and now in his comment he is concerned that there might be more than one taxon in the quarry (too many new sauropods). Which is it, and what aspects of our discussion of these problems in the paper does he find incomplete?

Claim 9: Jim’s photo of the reconstructed ilium shows that our reconstruction is wrong and that our conclusions are therefore suspect.

Source: Facebook, “I just realized that they reconstructed the ilium of Brontomeris [sic] wrong! See my Hotel Mesa album. It is not thunder thighs, but at most quivering thighs! I would say it throws a big hook into the entire thing.”

Response: Yesterday (February 23) we received an email from Jim, with this photo:

The body of the email:

I just realized that the ilium is reconstructed wrong in the paper. Here is how we reconstructed it straight in from the field..
Sorry guys.

Jim’s reconstruction includes a small piece of bone in the dorsal margin of the iliac crest that is not in our reconstruction. Here’s a comparison Mike put together to show which bits are which:

Jim’s reconstruction is different from ours, but that does not automatically make it correct. This just in by email (with permission to cite) from Brontomerus co-author Rich Cifelli, who is curator at the Oklahoma Museum of Natural History where the fossils are curated:

From: Rich Cifelli
To: Mathew Wedel, Mike Taylor
Date: 25 February 2011 00:45
Subject: restorations of Kirkland vs. Taylor et al.


I have re-examined the various pieces of the holotype ilium (OMNH 66430). Our restoration stands as the only one that is really plausible, and is the best match considering the thickness, curvature, preservation, and surface texture of the three main pieces (large section including acetabulum, peduncles, and pre-acetabular blade; followed by thin strip of margin; followed posteroinferiorly by “Oklahoma-shaped” piece with margin). The other piece shown by Kirkland (roughly rhomboidal in outline) was omitted by us because it does not include any of the bone margins (contra Jim’s restoration) or contacts with other pieces: it fit somewhere in the large space posterior to the pre-acetabular blade and dorsal to the acetabulum.

Kirkland’s restoration cannot be “straight from the field” because it is obviously incorrect in placement, orientation, and side shown for the rhomboidal piece. As said, this fragment does not contain any of the bone margin: all of the edges, including that which he depicts as lying along the posterior-posterodorsal margin of the ilium, are jagged and broken. Color, surface texture, and an important morphological feature also show that he depicts this piece upside down. That feature is a ridge which separated attachment places for two sacral ribs, shown by Kirkland to be lateral (facing outward) but which of course should be medial.

But, all right, suppose Jim had been right about how the pieces should fit together: here’s a new recon by Mike that follows the photo Jim sent.  Note that all the pieces fit comfortably within the very same dotted reconstruction line as in Fig. 2 of the paper.

It is also important to realize that the ilium is oriented differently in the two photos. The photo on the left in the comparison image, from Taylor et al. (2011: fig. 2), is a straight lateral view, looking straight down the laterally-oriented axis of the acetabulum. The preacetabular blade of the ilium angles out anterolaterally, as shown in our Figure 2B. In Jim’s photo, on the right of the comparison image, the preacetabular blade is lying flat on a table, which puts the acetabulum at an angle to the camera; the photo is effectively in posterolateral view rather than orthogonal, and this is the source of all the significant differences between the two photos. Take Jim’s reconstruction, mentally rotate it laterally through 20-30 degrees to look straight down the acetabulum, and his post-acetabular expansion would fit comfortably into the dotted line we drew, as Mike’s new recon shows.

The diagnostic features (autapomorphies) of the ilium are (Taylor et al. 2011: 78):

  1. Preacetabular lobe 55% of total ilium length, longer than in any other sauropod;
  2. Preacetabular lobe directed anterolaterally at 30 degrees relative to the sagittal plane, but straight in dorsal view and vertically oriented;
  3. Postacetabular lobe reduced to near absence;
  4. Ischiadic peduncle reduced to very low bulge;
  5. Ilium proportionally taller than in any other sauropod—height is 52% of total length, compared with a maximum of 45% in other sauropods.

If Jim’s reconstruction were right, it would only change the margin of the iliac crest, so it couldn’t affect characters 1, 2, or 4. His reconstruction still shows the postacetabular lobe reduced to near-absence (3), which still leaves the ilium proportionally taller than in any other sauropod (5).  In short, the version he favors doesn’t affect the proportions or autapomorphies one whit.

The alternative reconstruction is valuable because it points out the existence of a missing piece of the wing of the ilium. However, not only is it wrong in the position of that piece, even if it was right it wouldn’t affect our morphological, taxonomic, or functional interpretations of Brontomerus at all.


Thanks for slogging through this long, probably not-terribly-interesting post. We’ll soon return to normal service, with more information on Brontomerus — and that awesome life restoration.


Matt or I will probably post properly later today, but I just wanted to post a quick note to ask whether anyone has any printed (as opposed to online) newspaper copy on Brontomerus?  Although TV, radio and online coverage has been pretty good, I had the impression that it hardly made a dent in print at all, and in fact the only article I’ve seen is this tiny one in the Evening Standard (London’s free evening newspaper):

Evening Standard, Wednesday 23rd February 2011, page 2: London Experts discover Thunder Thighs

If anyone has printed copy other than this, I’d really appreciate it if they could send it to me.  (If it even exists.)  If that’s you, please leave a comment and post your clipping to:

Mike Taylor
Oakleigh Farm House
Crooked End
Gloucestershire  GL17 9XF


Today is the culmination of a project that I and Matt, and our co-author Rich Cifelli, are very proud of: the publication of the new sauropod, Brontomerus mcintoshi. Go and read the paper — it’s open access, thanks to the good folks at Acta Palaeontologica Polonica.

Speculative life restoration of the camarasauromorph sauropod Brontomerus mcintoshi from the Lower Cretaceous Cedar Mountain Formation of Utah. Adult individual (sized according to the referred scapula) protects juvenile (sized according to the holotype ilium) from a Utahraptor: the enlarged femoral protractors may have enabled a powerful kick. By Francisco Gascó. Reproduced with permission. (Taylor et al. 2011:fig. 12)

This project started for Matt many years ago — he first mentioned it to me on 15 May 2004, and we first discussed it in detail in July that year. It’s amazing to realise that very nearly seven years have slipped by since then. But it’s done at last, and Brontomerus mcintoshi is born today!

So, what is Brontomerus, and why should you care? It’s a kick-ass new sauropod — literally — which extends the range of known sauropod morphology and contributes to the growing record of Early Cretaceous sauropod diversity in North America. Plus its name means “thunder-thighs” and sounds kind of like Brontosaurus. What’s not to like?

Skeletal inventory of the camarasauromorph sauropod Brontomerus mcintoshi from the Lower Cretaceous Cedar Mountain Formation of Utah, in left lateral view. Preserved elements are white, missing elements are reconstructed in gray. After a Camarasaurus grandis reconstruction kindly provided by Scott Hartman. (Taylor et al. 2011:fig. 1)

We know Brontomerus from elements representing about 10% of a skeleton — not much, admittedly, but about 9% more than for Xenoposeidon. Oddly enough, for this blog, the two most informative elements are appendicular: a nearly complete and very weird left ilium, and most of a very nice and rather weird left scapula. We also have a single badly mangled presacral centrum (though even that is interesting), a single gorgeous caudal vertebra, a pair of partial sternal plates, and a bunch of dorsal ribs in various states of repair, of which one, probably the first from the right-hand side, is complete and — you guessed it — weird. (No cervical ribs, though.) There are a few more fragments, but they’re uninformative.

We know that not all this material is from a single animal, because it’s of wildly different sizes: based on the relative sizes of scapula and ilium in Rapetosaurus, we estimated that the animal that contributed the scapula is about three times as long in linear dimension (and so about 3^3 = 27 times as massive) as the much smaller beast that kindly donated its ilium. “But wait!”, you cry: “If the bones are not all from the same individual, what makes you say they’re all from the same taxon?” Patience, young padawan; we will discuss this at length later this week (hereafter PYP;WWDTALLTW).

Because the ilium is the most distinctive of the bones, we nominated it as the holotype. “But wait!”, you cry: “If the ilium is from a juvenile individual, surely it’s not suitable to be the holotype?” PYP;WWDTALLTW.

Left ilium of the camarasauromorph sauropod Brontomerus mcintoshi from the Lower Cretaceous Cedar Mountain Formation of Utah, type specimen OMNH 66430 in lateral view reconstructed from the three fragments (A), and ventral view (B). (Taylor et al. 2011:fig. 2)

We diagnosed Brontomerus by five autapomorphies of the holotype ilium: preacetabular lobe 55% of total ilium length, longer than in any other sauropod; preacetabular lobe directed anterolaterally at 30° to the sagittal, but straight in dorsal view and vertically oriented; postacetabular lobe reduced to near absence; ischiadic peduncle reduced to very low bulge; ilium proportionally taller than in any other sauropod, 52% as high as long. What does all that mean? PYP;WWDTALLTW. (Wow, that acronym is turning out to be more useful than I expected.) In briefest summary, it’s nothing like any other sauropod ilium I’ve ever seen; and that’s not because it’s from a juvenile.

Brontomerus has had a slightly odd publication history: it was inadvertently published as an “accepted manuscript” on the Acta web-site on 3rd January, whence it was quickly picked up by the Dinosaur Mailing List. In a matter of hours, a Wikipedia article appeared, along with mentions on a surprising number of web-sites: as I write this, four days before publication, Google has 60 hits for “brontomerus” including pages from Germany, Holland, the Czech Republic, Poland and Argentina. But the Acta people were very fast to take down the accepted manuscript once I’d pointed out that the name was being accidentally leaked, and I was able to have the Wikipedia article deleted pretty quickly too. It seems that, against all expectation, the genie was pretty much put back in the bottle.

As if that weren’t enough failage to be going on with, I (Mike) accidentally posted this very article a couple of days before publication.  D’oh!  (WordPress’s Publish button is terribly easy to hit.)  Again, we scrambled to try to limit the damage.  I was able to un-publish the article itself, but by then it had already gone out by RSS, so some of you might have seen this post before in that earlier form.  (This is of course the reason for the I’m Stupid post.)

All the rushing around to shut down premature announcements was, of course, intended to keep the powder dry for today; and we heartily encourage all of you who’ve been wanting to to talk about Brontomerus to do so now!

Back row (L to R): Mike Taylor, Matt Wedel, Rich Cifelli; front row, Brontomerus

There is a lot more that we could say — and will say — about Brontomerus. We have a bunch more posts planned for later in the week, as noted above.  Those of you who can’t wait will of course read the paper, but may also find yummies on the press-pack page or the unofficial online supplementary information.