February 26, 2011
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.
- Curry Rogers, Kristina. 2009. The postcranial osteology of Rapetosaurus krausei (Sauropoda: Titanosauria) from the Late Cretaceous of Madagascar. Journal of Vertebrate Paleontology 29:1046-1086.
- Janensch, Werner. 1961. Die Gliedmaszen und Gliedmaszengurtel der Sauropoden der Tendaguru-Schichten. Palaeontographica, suppl. 7 (1), teil 3, lief. 4: 177-235.
- Lehman, Thomas M. and Alan B. Coulson. 2002. A juvenile specimen of the sauropod dinosaur Alamosaurus sanjuanensis from the Upper Cretaceous of Big Bend National Park, Texas. Journal of Paleontology 76(1):156-172.
- Osborn, Henry Fairfield, and Charles 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.
- Taylor, Michael P., Mathew J. Wedel and Richard L. Cifelli. 2011. A new sauropod dinosaur from the Lower Cretaceous Cedar Mountain Formation, Utah, USA. Acta Palaeontologica Polonica 56(1):75-98. doi: 10.4202/app.2010.0073
February 25, 2011
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’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):
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). [...]
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..
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):
- Preacetabular lobe 55% of total ilium length, longer than in any other sauropod;
- Preacetabular lobe directed anterolaterally at 30 degrees relative to the sagittal plane, 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—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.
- Chure, D., Britt, B.B., Whitlock, J.A., and Wilson, J.A. 2010. First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition. Naturwissenschaften (online preprint). doi:10.1007/s00114-010-0650-6
- Kirkland, J. I., Zanno, L. E., Sampson, S. D., Clark, J. M. and DeBlieux, D. D. 2005. A primitive therizinosauroid dinosaur from the Early Cretaceous of Utah. Nature 435: 84-87.
- Taylor, M. P., Wedel, M.J., and Cifelli, R.L. 2011. A new sauropod dinosaur from the Lower Cretaceous Cedar Mountain Formation, Utah, USA. Acta Palaeontologica Polonica 56(1):75-98. doi: 10.4202/app.2010.0073
February 24, 2011
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):
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:
Oakleigh Farm House
Gloucestershire GL17 9XF
February 23, 2011
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 the paper — it’s open access, thanks to the good folks at Acta Palaeontologica Polonica.
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?
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 and (you guessed it) weird 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 singe 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.
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, indended 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!
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.
February 20, 2011
Earlier this evening, while I was editing an SV-POW! article that we plan to release on Wednesday, I (Mike) inadvertently hit the Publish button rather than Save Draft as I’d intended. I was able to quickly undo the posting, but it’s possible that some of you may have seen Wednesday’s article prematurely, especially if you use an RSS reader that happened to cache that page during the brief period that it was available.
I am asking you all, please, to limit the damage from my stupidity by not discussing that article or its subject at all until Wednesday. Please don’t even say what it was about.
Thanks for understanding.
February 17, 2011
(This is sort of a riff on the recent post, Tutorial 12: How to find problems to work on, which you might want to read first if you haven’t already.)
Something that has been much on my mind lately is the idea that if you don’t go too far, you don’t know how far you should have gone.
I first encountered this idea in a quote from concept artist Ian McCraig, in The Art of Star Wars: Episode I (p. 195):
People ask when I know when to stop scribbling, and decide a work is finished. I say you have to go too far and destroy it, because then you know when you should have stopped and can go back. If you don’t, you leave untold riches out there.
I’m sure McCraig wasn’t the first to formulate the idea, he’s just the medium through which I first learned of it, back in 1999.
Scott Aaronson calls brief statements of this sort “Umeshisms“, after his advisor, Umesh Varizani, who said,
If you’ve never missed a flight, you’re spending too much time in airports.
A follow-up post, reporting the results of an Umeshism contest among his readers, also has some gems.
For the sake of completeness, I should note the very economical general formulation of this idea from Tagore Smith, in a comment on Mike’s blog that Mike later promoted into a stand-alone post (the comment, not this excerpt):
I haven’t gone too far yet so I am not sure if I have gone far enough.
Here’s the larger lesson Aaronson drew from his advisor’s airport quip:
In a single sentence, Umesh was communicating an entire philosophy of life: concentrate on the high-order bits. The squash player who runs back and forth to attempt every shot, the student who’s never late with an assignment, the researcher who stalks an unimportant problem like Captain Ahab: all have succumbed to the tyranny of the low-order bit. They need to realize that, as in a randomized algorithm, occasional failures are the inevitable byproduct of a successful strategy. If you always win, then you’re probably doing something wrong.
One of the reasons this is so much on my mind is that I did an editing pass on a manuscript Mike is working on, and he took some of my suggestions, but not all of them. And I realized that that is probably a good thing; if he’d taken all of my suggestions, it would mean that I not edited hard enough. And it occurred to me that the Umeshism philosophy can probably be more effectively implemented by two people than by one. One can’t be an iconoclast all the time and still be productive; you have to settle down sometime. Also, two sets of eyes are going to see more ways to push the edge of the envelope.
“The researcher who stalks an unimportant problem like Captain Ahab” is also worth thinking about–specifically, to wonder which among my many concurrently developing projects are high-order bits, and which are not. Mike and I refer to our lists of works-in-progress as POOP, or Prioritized Ordering Of Projects, but we (or at least I) tend to slip into using “priority” to mean, “what am I working on next”, and not, “what should I be working on next”. I have let many projects slip into limbo while pursuing others, and it would be worthwhile to periodically reassess whether I’ve let the right ones slip. I strongly suspect that it has not always been the case. I just wrote in Tutorial 12 that any productive researcher is going to die with a mountain of intended work left undone. It is probably not too early for any of us to look at our array of projects and ask, “Which among these most needs rescuing from that mountain?”
The long Aaronson quote above also raises the specter of the costs of catching mistakes, which Paul Graham and Mike have both written essays about. Both basically boil down to “safety is expensive”. And that is sort of what I meant in Tutorial 12 when I wrote, “If you’re not feeling stupid, you’re too comfortable, and it might be time to do an audit and see if you’re actually contributing to science at all.” Feeling stupid–in the scientifically productive way–is a symptom of being out of your safety zone, where you are more likely to learn valuable things and have new ideas. I also argued that you have to sift through a lot of facts and ideas to hit on the handful that might meaningfully become part of your research. Most of the stuff you encounter will not be relevant to whatever it is you’re trying to do, but that’s okay. If all of your ideas seem like good ones, either you’re playing it very safe (and therefore the ideas aren’t actually that good), or you’re having delusions of grandeur.
I remember seeing somewhere–irritatingly, at this point I have no idea where–some guy arguing, maybe half-seriously, that any project was plagued both by errors that one knows about and also by other errors or biases of which we are ignorant, and that therefore he always tried to make sure that his known errors were bigger, because that way he was in control (the original was more cleverly and economically phrased).
All of this interests me, because so many forces in our lives conspire to make us afraid of making mistakes, and often even more afraid of admitting to them once they’ve been made. But we all make mistakes, all the time. So what are we going to do about it?
Right now my Gmail sig quote is a line from Clay Shirky:
To put yourself forward as someone good enough to do interesting things is, by definition, to expose yourself to all kinds of negative judgments, and as far as I can tell, the fact that other people get to decide what they think of your behavior leaves only two strategies for not suffering from those judgments: not doing anything, or not caring about the reaction.
The hardest reaction to not care about is your own. Doing good work demands the capacity to take mistakes in stride and keep moving forward. Doing great work might require another level of perspective, in which some kinds of mistakes are just indicators that you’re on the right path.
February 17, 2011
I have just made a series of fairly major edits to the in-progress Checklist for new zoological genera and species, and wanted to explain what’s changed and why.
The important change is that the Checklist no longer attempts to encompass the creation of families, nor of all genus-group and species-group names — only genera and species. I took this painful decision after a lot of consultation with various people, here and by email, despite wanting the utility of the Checklist to be a broad as possible. In the end, it became apparent that the attempt to include these other ranks could only result in the Checklist becoming much much longer and more complex, or leaving loopholes, or more likely both.
- The very terms “genus-group” and “species-group” are misleading to non-specialist taxonomists — they can easily be misunderstood as meaning “group of genera” and “group of species”.
- While the Code indicates that the only species-group ranks are species and subspecies, superspecies are fairly often used as well, and we don’t want to get into discussing such matters.
- Likewise, supergenera are sometimes used as well as genera, despite the lack of support in the Code.
- Conversely, the Code’s definition of genus-group names (see the Glossary) include things called “collective groups”, whatever they may be.
- Worse, the Code also talks about divisions, which are described in the Glossary, not particularly helpfully, as “(1) A rank that if treated as a division of a genus or subgenus is deemed to be of subgeneric rank for the purposes of nomenclature [Art. 10.4]. (2) A taxon at the rank of division.” We just don’t want to get into that stuff.
- Discussion of subgenera and related ranks on the ICZN mailing list has resulted in disagreement even between taxonomy specialists on that list, over matters such as whether a subgenus can be used as the type genus of a family. When even experts disagree, it seems a fool’s errand for the Checklist to try to tersely summarise the rules.
In short, I became convinced that trying to have the Checklist cover ranks other than genera and species opened up all sorts of cans of worms, and that the target audience — zoologists who are not taxonomy specialists — will get more value from a checklist that is more limited in scope, simpler to understand, and shorter.
As usual, comments are closed on this brief update — not to stifle debate, but because I want to keep all discussion together in one place: so please head over to the draft Checklist, read through the current version, and post any comments you may have.
I am optimistic that we are converging now on a version that is as simple as possible but no simpler. Once we freeze in a few days, we will hopefully move to the next phase … which I’ll tell you about at the time.
February 14, 2011
Sorry to bump Matt’s awesome Rhea-neck post off the top of the SV-POW! home page, but I have news of the rapidly developing checklist for new zoological names. As well as many, many minor and not-so-minor edits — and thanks to everyone who’s participated in this process — I have made a major structural change.
The list has been broken into two, first enumerating Requirements and then describing Best Practice. I have also reordered some of the points within lists. As a result, ALL NUMBERING HAS CHANGED; also some points have been split and others merged.
Please be sure to comment only on the most recent version.
I am worried that the Checklist is getting too big. I just copied and pasted the substance of it — the introductory paragraph and the two lists — into a new OpenOffice in 12-point Times, and found that it runs to a page and a quarter. Reduced to 10.5-point type it fits on a page, but that’s the way I want to go. So suggestions for reducing the length without losing content will be particularly welcome.
(As before, comments are closed on this post, because I don’t want to split discussion between here and the checklist itself.)
February 12, 2011
When you last saw this rhea neck, I was squeezing a thin, unpleasant fluid out of its esophagus. Previous rhea dissection posts are here and here; you may also be interested in my ratite clearing house post.
We did that dissection back in 2006. Since then I finished my dissertation, got a tenure-track job, and moved twice. The rhea neck followed me, living in a succession of freezers until last spring.
Last spring I thawed it out, straightened it (it had been coiled up in a gallon ziploc), refroze it, and had it cut in half sagittally with a bandsaw. I did all of this for a project that is not yet ready to see the light of day, but there’s a ton of cool morphology here that I am at liberty to discuss, so let’s get on with it.
Throughout the post, click on the images for full resolution, unlabeled versions.
In the image above, you’ll notice that the saw cut was just slightly to the left of the midline, so that almost the entire spinal cord was left in the right half of the neck (the one toward the top of the image; the left half, below, is upside down, i.e. ventral is towards the top of the picture). The spinal cord is the prominent yell0w-white stripe running down the middle of the hemisectioned neck. It’s a useful landmark because it stands out so well. Dorsal to it are the neural arches, spines*, and zygapophyses of the vertebrae, and epaxial muscles; ventral to it are the vertebral centra and the hypaxial muscles.
* If you want to call them that–some of them are barely there!
Here’s the large supraspinous ligament (lig. elasticum interspinale), which is similar to the nuchal ligament of mammals but independently derived. Compare to the nuchal ligament of a horse (image borrowed from here):
Note how the actual profile of the neck is vastly different from what you’d suspect based on the skeleton alone. This is one of the reasons that necks lie. For more on the supraspinous ligament in rheas and its implications for sauropods, see Tsuihiji (2004) and Schwarz et al. (2007).
Birds also have very large interspinous ligaments (lig. elasticum interlaminare), each of which connects the neural spines of two adjacent vertebrae. In the above photo, the blunt probe is passing under (= lateral to) the unpaired, midline interspinous ligament. Rheas are unusual among birds in having such a large supraspinous ligament, and you can see that this interspinous ligament is almost as big. If you tear down the neck of a chicken or turkey, you will find huge interspinous ligaments, and the supraspinous ligament will be tiny if you can identify it at all.
Here’s something I don’t think we’ve ever shown before here on SV-POW!: a photograph of an actual pneumatic diverticulum. That’s the dark hole in the middle of the photo. You can see that we’re in the left half of the neck, lateral to the spinal cord, almost to the postzygapophysis, the articular surface of which is more lateral still (“below” or “deep to” the surface you see exposed in this cut). Usually at each intervertebral joint there is a connection between the lateral pneumatic diverticula that run up the side of the cervical column and pass through the cervical rib loops and the supramedullary diverticula that lie dorsal to the spinal cord inside the neural canal. That connecting diverticulum is the one exposed here.
NB: diverticulum is singular, diverticula is plural. There are no diverticulae or, heaven forbid, diverticuli, although these terms sometimes crop up in the technical literature, erroneously. (I hesitate to point this out, not because it’s not important, but because I’ll be lucky if I didn’t screw up a Latin term elsewhere in the post!)
Here are pneumatic diverticula in a transverse CT section of an ostrich neck (Wedel 2007b: fig. 6; compare to Wedel 2003: fig. 2, another slice from the same neck). In this view, bone is white, muscles and other soft tissues are gray, and air spaces are black. A, lateral diverticula running alongside the vertebral centra. B, air spaces inside the bone. C, supramedullary airways above the spinal cord. This section is close to the posterior end of a vertebra; the flat-bottomed wing-like processes sticking out to either side are the anterior portions of the postzygapophyses. If the slice was a few mm more posterior, we would see the prezygapophyses of the preceding vertebra in contact with them. Also, the vertical bars of bone connecting the centrum to the postzygs would pinch out, and we’d see the diverticula connecting the lateral (A) and supramedullary (C) airways–that’s the diverticulum revealed in the photo two images up.
Here’s another cool section showing a diverticulum and some muscles. Note the short interspinous muscles, which connect the neural spines of adjacent vertebrae. The probe indicates another open diverticulum, and the very tip of the probe is under one of the very thin layers of epithelium that line the diverticula. You can see that this diverticulum lies on the dorsal surface of the vertebra, posterior to the prezygapophysis and anterior to the neural spine. This supravertebral diverticulum is near and dear to my heart, because I have published an image of its traces before.
Lots going on in this photo (remember that you can click for an unlabeled version). This is a middle cervical vertebra of an emu, in anterodorsal view, with anterior towards the bottom of the picture. Bonus geek points if you recognized it as the basis for Text-fig. 9 in Wedel (2007a). I published this photo in that paper because it so nicely illustrates how variable the skeletal traces of pneumaticity can be, even from left to right in a single bone. On the right side of the photo (left side of the vertebra), the bone resorption adjacent to the supravertebral diverticulum produced a pneuamtic fossa, but one without distinct bony margins or a pneumatic foramen. On the other side, the fossa contains a pneumatic foramen which communicates with the internal air spaces, but the fossa is otherwise identical. Fossae like the one on the right are a real pain in the fossil record, because they might be pneumatic, but then again they might not be; such shallow, indistinct fossae can house other soft tissues, including cartilage and fat. This is what I was talking about when I wrote (Wedel 2009: p. 624):
If progressively more basal taxa are examined in the quest to find the origin of PSP [postcranial skeletal pneumaticity], the problem is not that evidence of PSP disappears entirely. It is that the shallow, unbounded fossae of basal dinosaurs are no longer diagnostic for pneumaticity.
For more on that problem, see Wedel (2007a) and the post, “X-Men Origins: Pneumaticity”.
The other labelled bits in the above photo are all muscle attachment points, and you may find Wedel and Sanders (2002), especially Fig. 2, a useful reference for the rest of the post. The dorsal tubercles, or epipophyses, are rugosities dorsal to the postzygapophyses that anchor most of the long, multi-segment epaxial muscles, which in birds are the M. longus colli dorsalis, which originates on the anterior faces of the neural spines, and M. ascendens cervicalis, which originates on the cervical rib loops. The crista transvers0-obliqua is a low, bony crest connecting each dorsal tubercle to the neural spine; it corresponds to the spino-postzygapophyseal lamina (SPOL) of sauropods (see Tutorial 4: Laminae!), and anchors the Mm. intercristales, a group of short muscles that span the cristae of adjacent vertebrae, like the Mm. interspinales only more lateral.
The carotid tubercles serve as points of origin for the M. longus colli ventralis, one of the largest and longest of the multi-segment hypaxial muscles; they have no obvious homolog or analog in sauropods. The lack of this feature might indicate that the hypaxial muscles were less of a big deal in sauropods, for whom lifting the neck was presumably a bigger problem than lowering it. Alternatively, the M. longus colli ventralis of sauropods might have attached to the medial sides of the parapophyses and the capitula of the cervical ribs, which tended to be larger and more ventrally-directed than in basal sauropodomorphs and theropods.
The unlabeled red arrows mark the lateral tubercles and crests of the cervical rib loop, to which we will return momentarily.
Here you can see a big bundle of long epaxial muscles, including both the M. longus colli dorsalis and M. ascendens cervicalis, inserting on the left dorsal tubercle of the vertebra on the right. Note that the cut here is quite a bit lateral of the midline, and actually goes through the lateral wall of the neural canal in the vertebra on the right (that vert is the fifth back from the front of the section of neck featured in this post, which is incomplete). That is why you see the big, multi-segment muscles here, and not the shorter, single-segment muscles, which lie closer to the midline.
Here are some more muscle attachment points in a bird vertebra (a turkey this time, courtesy of Mike). The lateral crests and tubercles (tubecula ansae and cristae laterales, if you’re keeping track of the Latin) are the same bony features indicated by the red arrows in the photo of the emu vertebra up above. They anchor both the long M. ascendens cervicalis, which inserts on the dorsal tubercles of more anterior vertebrae, and the short Mm. intertransversarii, which span the cervical rib loops of adjacent vertebrae. Sauropods usually have at least small rugosities on their diapophyses and the tubercula of their cervical ribs (which articulate with the diapophyses) that probably anchored homologous muscles.
Here’s a dorsal tubercle above the postzyg on the neural arch of a juvenile Apatosaurus (cervical 6 of CM 555, shown in right lateral view). Notice that the spinopostzygapophyseal lamina (SPOL) and postzygodiapophyseal lamina (PODL) actually converge on the dorsal tubercle rather than on the postzyg. This is pretty common, and makes good mechanical sense.
Dorsal tubercles again, this time on the world’s most wonderful fossil, cervical 8 of the HM SII specimen of Giraffatitan brancai, in the collections of the Humbolt museum in Berlin. While you’re here, check out the pneumato-riffic sculpting on the lateral faces of the neural arch and spine, and the very rugose texture on the tip of the neural spine, SPOLs, and dorsal tubercles. In fact, compare the numerous pocket-like external fossae on this vertebra with the internal air cells exposed in the cross-sectioned rhea neck. I have argued here before that sauropod cervical vertebrae are pretty similar to those of birds; the main differences are that the cervical rib loops are proportionally much smaller in sauropods, and sauropod vertebrae mostly wore their pneumaticity on the outside.
Farther anteriorly in the neck–the three vertebrae pictured here are the third, fourth, and fifth (from right to left) in this partial neck–and somewhat closer to the midline. Now you can see some short epaxial muscles, probably Mm. intercristales and Mm. interspinales (the two groups grade into each other and are often not distinct), spanning adjacent vertebrae. As in several previous photos, the supravertebral diverticulum is visible, as well as the communicating diverticulum that connects the lateral diverticula to the supramedullary airways. I forgot to label them, but ventral to the centra you can see long, light-colored streaks running through the hypaxial muscles. These are the tendons of the M. longus colli ventralis, and in some of the previous photos you can see them running all the way to their origination points on the carotid tubercles. These extend posteriorly from the short cervical ribs of birds, and are homologous with the long cervical ribs of sauropods.
That’s all I have for this time. If you’d like to see all of this stuff for yourself, turkey necks are cheap and big enough to be easy to work with. Geese are good, too. You can see all the same bits in a chicken or a duck, it’s just harder because everything is smaller (if you’re a real glutton for punishment, try a Cornish game hen).
When I first started working on sauropods, their cervical vertebrae made no sense to me. They were just piles of seemingly random osteology. The first time I dissected a bird neck was an epiphany; ever since then, it is hard for me to look at sauropod vertebrae and not see them clad in the diverticula and muscles that shaped their morphology. Go have fun.
- Schwarz, D., Frey, E., and Meyer, C.A. 2007. Pneumaticity and soft−tissue reconstructions in the neck of diplodocid anddicraeosaurid sauropods. Acta Palaeontologica Polonica 52(1):167–188.
- Tsuihiji, T. 2004. The ligament system in the neck of Rhea americana and its implications for the bifurcated neural spines of sauropod dinosaurs. Journal of Vertebrate Paleontology 24: 165–172.
- Wedel, M.J. 2003a. Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs. Paleobiology 29:243-255.
- Wedel, M.J. 2007a. What pneumaticity tells us about ‘prosauropods’, and vice versa. Special Papers in Palaeontology 77:207-222.
- Wedel, M.J. 2007b. Aligerando a los gigantes (Lightening the giants). ¡Fundamental! 12:1-84. [in Spanish, with English translation]
- Wedel, M.J. 2009. Evidence for bird-like air sacs in saurischian dinosaurs. Journal of Experimental Zoology 311A(8):611-628.
- Wedel, M.J., and Sanders, R.K. 2002. Osteological correlates of cervical musculature in Aves and Sauropoda (Dinosauria: Saurischia), with comments on the cervical ribs of Apatosaurus. PaleoBios 22(3):1-6.