March 17, 2015
I have a new paper out today in PeerJ: “Ecological correlates to cranial morphology in leporids (Mammalia, Lagomorpha)”, with coauthors Brian Kraatz, Emma Sherratt, and Nick Bumacod. Get it free here.
I know, I know, I have fallen from grace. First Aquilops, now rabbits. And, and…skulls! I know what you’re thinking: that maybe I’m not just experimenting with the non-vertebrae of non-sauropods anymore – maybe I have an actual problem. But I don’t. I can quit anytime! You’ll see.
Actually rabbits are the freakiest of all mammals and their skulls are wicked cool. They have double incisors, with the second set right behind the first, hence the name Duplicidentata for rabbits and their close relatives. They have weird fenestrations in their maxillae (pretty much all taxa) and parietal and occipital bones (some more than others) – I’ll come back to that in a bit. And, as we discuss in our new paper, you can tell something about how a rabbit runs by looking at its skull. I thought it would be fun to relate how we figured that out, and why.
A long time ago in a graduate seminar far, far away…
1950: DuBrul, Laskin, and Moss
I met Brian Kraatz at Berkeley, where he and I were part of the cohort of students that came into the Integrative Biology Department in the fall of 2001 (faithful readers may remember Brian from his work tracking oliphaunts from, gosh, three years ago already). We took a lot of classes together, including a seminar by Marvalee Wake on evolutionary morphology. I’m pretty sure that seminar was the first time I’d actually read DuBrul and Laskin (1961), “Preadaptive potentialities of the mammalian skull: an experiment in growth and form”, or as I think of it, “How to turn a rat skull into a pika skull for fun and profit.”
Pikas (Ochotonidae) are the sister group to rabbits (Leporidae) and together these groups make up crown Lagomorpha. If you’re not familiar with pikas, Brian describes them as starting with bunny rabbits and then making them even cuter and cuddlier. Seriously, go do an image search for ‘pika’ and try not to die of cute overload.
Pikas are interesting because in many ways their skulls are intermediate between those of rodents, especially rats, and rabbits. This is maybe not surprising since rodents are the sister group to lagomorphs and are united with them in the clade Glires. E. Lloyd DuBrul was all over this rat-pika-rabbit thing back in the mid-twentieth century. Here’s an illustration from DuBrul (1950: plate 2; labels added by me):
So DuBrul knew from pikas and in particular he had the idea that you could maybe just tweak a rat skull – say, by knocking out the basicranial sutures in a baby rat to limit the growth of the skull base – and produce a gently domed skull like that of a pika. That’s what DuBrul and Laskin (1961) is all about. They did that experiment and here are their results (DuBrul and Laskin (1961: plate 3). Normal rat skull on the right, and dotted in the bottom diagram; experimental “pika-morph” rat skull on the left, and solidly outlined below.
What’s going on here morphogenetically is that the facial skeleton is getting tilted down and away from the back end of the skull. DuBrul was hip to that, too – here’s a relevant image from his 1950 paper (plate 4; labels added by me):
The common reference point against which these skulls are registered is the cranial base (the floor of the braincase just forward of the foramen magnum). Again, the pika is a pretty good intermediate between the rat and a ‘normal’ rabbit, and the dang-near-dog-sized Flemish Giant rabbit takes the lagomorph face-tilting thing to its extreme. (‘Flemish Giant rabbit’ is another entertaining image search that I will leave you as homework.)
Turns out there’s another way you can get rat skulls with different geometries: you can cut off their legs and make them walk on two feet. In an experiment that you might have trouble getting past an Institutional Animal Care and Use Committee today, Moss (1961) lopped off the forefeet or hindfeet in two experimental batches of rats, to see what effect this would have on their skulls. I’ll let Moss speak for himself on this one (Moss, 1961: pp. 301-303, emphasis in the original):
Circumnatal amputation of the forelimbs has successfully produced what are in essence “bipedal rats,” i.e., rats whose habitual mode of kinetic and static posture is permanently altered. […] The animals never became bipedal in the exact sense; that is, they never walked erect on two limbs at all times. […] Nevertheless, bipedal posture and motion were more frequently observed than in controls. […]
Animals whose hind limbs were removed represented another picture. They most certainly did not walk about on their intact forelimbs. Neither did they seem able to use their hind limb stumps as satisfactory substitutes. Their gait was not uniform and seemed to consist in a series of short pushes or hops. The most noticeable thing about them was, among other things, apparent accentuation of their cervical vertebral curvature. The sum of these changes was an upward rotation of the skull.
He wasn’t kidding: when the two groups of bipedal rats grew up, their facial skeletons were tilted relative to the control group, but in different directions (Moss, 1961: fig 3; ‘fore’ and ‘hind’ refer to which limbs the animals had left to locomote with):
Brian and I read Moss back at Berkeley, too. In fact, we were minor Moss junkies. If you’re interested in how living forms come into being, you owe it to yourself to read Moss (1968), “A theoretical analysis of the functional matrix”.
The upshot of all of this is that although neither Brian nor I had done anything with our deep (and, okay, deeply weird) knowledge of how to experimentally jack up rat skulls by the time we graduated from Berkeley, we were also primed to be thinking about how skulls attain their shapes – especially the skulls of rodents and rabbits.
2009: American Museum of Natural History
I went to the AMNH in February, 2009, to visit Brian, who was on a postdoc there at the time, and to spend one day looking at sauropods with Mike, who was over from England for a conference. What Brian and I planned to work on was the fenestration of rabbit skulls, because I’m always interested in the strategic loss of bone from skeletal structures. We spent probably half a day talking about that, and I filled a whole page in my notebook with related noodlings:
But as the sketch on the right shows, it didn’t take us long to figure out that there was something even more interesting to do with rabbit skulls. Brian had a whole shedload of rabbit skulls from different taxa sitting on his desk, and we noticed pretty quickly that one of the primary ways they varied was in the tilt of the facial skeleton relative to the back of the skull. Here’s the very next page of my notes from that trip:
The skull up top belongs to Caprolagus, the Hispid hare, which I tend to think of as the “bulldozer hare”. Seriously, it looks like a tank. It doesn’t bound or even hop, it scrambles. Here, stare into the abyss:
That rabbit will cut you, man. And just look at how flat its skull is. Even in life Caprolagus looks more rodent-y than rabbit-y. Or, more precisely, more Ochotona-y.
At the the other extreme are taxa like Bunolagus and Pronolagus, which really push the “I’m going to cute you to death by dint of my incredible bunnosity” thing:
As Brian and I started going through skulls of as many extant rabbits as we could, we noticed that the flatter-skulled taxa, with less pronounced facial tilt, tended to be the stolid, foursquare scramblers like Caprolagus, whereas the speed demons tended to have more strongly tilted skulls. It also seemed like the latter group were achieving that pronounced facial tilt by changing the geometry of the occipital region of the skull. Look back up at the red quadrilaterals I drew on the Caprolagus and Bunolagus skulls in my notebook – those mark the basioccipital ventrally and the dorsal exposure of the supraoccipital. Perhaps unsurprisingly, supraoccipital length is not the whole story; it turns out that some face-tilters get that way by having longer or more strongly arched parietals, BUT it remains true that if you find a rabbit skull with a long dorsal exposure of the supraoccipital, it will also have pronounced facial tilt.
ANYWAY, by my last night in New York, Brian and I decided that the best way to attack this would be to go down to the basement and stay up most of the night drinking beer and measuring rabbit skulls. We then tried to correlate the various measurements and angles with information on the locomotor and burrowing habits of each species. That was a big job, after a couple of years with little forward progress (to be fair, Brian was moving across the country and taking his first tenure-track job in this interval, and I was helping birth a sauropod) we brought in Brian’s graduate student, Nick Bumacod, to do most of it. Later on the three of us were forced to acknowledge that we knew enough statistics to get ourselves into trouble but not enough to get back out. Brian had taken a geometric morphometrics course for which Emma Sherratt was a TA, and he started bugging her for help with the stats. Emma has been involved in writing new software packages for R, and we realized that the paper would be a lot stronger if we just brought her on as an author and gave her free rein with the data. Along the way Brian and Nick were giving presentations on the project everywhere from the local Western Area Vert Paleo meeting to the World Lagomorph Conference in Vienna. I got my name on four abstracts along the way, which I think is record abstract-to-paper ratio for me (especially considering that 90% of my effort on the paper was invested in a single evening in 2009 over a couple of six-packs).
But enough navel-gazing, what did we find?
2015: Rabbit skulls reveal their mode of locomotion
Our results, which you can read for free, support the hunch that Brian and I had back in 2009: slow-moving rabbits that locomote by scrambling or scampering instead of hopping tend to have less facial tilt, and faster-moving saltatorial (hopping) and cursorial (leaping and bounding) rabbits have more facial tilt. Interestingly, facial tilt does not distinguish the saltators from the cursors. So the break here is between scrambling and any kind of hopping or leaping, but not between hoppers and leapers.
Why would that be so? We don’t for sure yet, but our top hypothesis is that if you’re moving fast, it pays to see the ground in front of you more clearly, and getting your nose down out of the way probably helps with that. This is pretty similar to the hypothesis that tyrannosaurs have pinched nasals for better binocular vision (Stevens, 2006). Rabbits are prey animals and probably can’t afford to point their eyes forward, and they may need wide nasal airways as air intakes while they’re sprinting. Tilting the nose down may be the next best thing.
Some circumstantial support for this comes from the Caviidae, the family of South American rodents that includes guinea pigs, cavies, maras, and capybaras. Here’s another plate from DuBrul (1950: plate 6) contrasting the flatter skull of the guinea pig (Cavia porcellus, top) with the decidedly arched skull of the mara or Patagonian hare (Dolichotis magellanica, bottom). Compare the mara skull to the sectioned rabbit skull in the other DuBrul plate, above – there aren’t a lot of obvious characters to separate the two (beyond the lack of double incisors in the mara).
Despite being commonly referred to as ‘hares’ and looking a lot like short-eared rabbits, maras are rodents that evolved their rabbit-like form independently. The acquisition of pronounced facial tilt in two separate lineages of small fast-moving herbivorous mammals is further evidence for the influence of locomotor mode on skull form. Irritatingly, I think we neglected to mention the guinea pig : mara :: pika : rabbit correspondence in the paper. Oh well, it wasn’t our novel observation, and we did cite DuBrul (1950).
We found lots of other interesting things, too. The PCA plots we produced from our data separate the living rabbits in unexpected ways. The length of the diastema (the toothless portion of the upper jaw) and the diameter of the auditory bulla seem to be particularly important. Diastema length isn’t too hard to figure out – most of the face-tilters have long diastemas, and the flat-heads tend to have short ones. We have no idea what bulla diameter means yet. I mean, obviously something to do with hearing, but we don’t have any ecological variables in our analysis to address that because we didn’t see it coming. So there’s a chunk of new science waiting to be done there.
Speaking of new science, or at least a relatively new thing in science, we published the full peer-review history alongside the paper, just as Mike and I did back in 2013 and as Mike did with his stand-alone paper last December. More than 80% of PeerJ authors elect to publish the peer review histories for their papers. I can’t wait until it’s 100%. PeerJ reviews are citeable – each one gets a DOI and instructions on how to cite it – and I’m tired of having my effort as a peer reviewer used once and then thrown away forever.
If you’ve been reading this whole post with gritted teeth, wondering why we were using linear measurements instead of geometric morphometrics, chillax. Brian and Emma are on that. They’ve been CT scanning the skulls of as many extant rabbits as possible and plotting landmarks for 3D morphometrics – if you were at SVP last fall, you may have seen their talk (Kraatz and Sherratt, 2014). So stay tuned for what will soon be a new ongoing series, Rabbit Skulls: The Next Generation.
I probably won’t be on that voyage. I’ve had fun getting acquainted with a completely different part of the tree of life, but there are an awful lot of shards of excellence – busted-up sauropod vertebrae, that is – crying out for my attention, and I need to stop neglecting them. I’m done with rabbit skulls, I promise. I’m going clean. (Wish me luck!)
- DuBrul, E. L. (1950). Posture, locomotion and the skull in Lagomorpha. American Journal of Anatomy, 87(2), 277-313.
- DuBrul, E. L., & Laskin, D. M. (1961). Preadaptive potentialities of the mammalian skull: an experiment in growth and form. American Journal of Anatomy, 109(2), 117-132.
- Kraatz, B., and Sherratt, E. (2014). Evolution, ecology, and modularity of the lagomorph skull. Journal of Vertebrate Paleontology, 35(3, Supplement), 162A.
- Kraatz, B.P., Sherratt, E., Bumacod, N., and Wedel, M.J. 2015. Ecological correlates to cranial morphology in leporids (Mammalia, Lagomorpha). PeerJ, 3:e844. https://dx.doi.org/10.7717/peerj.844
- Moss, M. L. (1961). Rotation of the otic capsule in bipedal rats. American Journal of Physical Anthropology, 19(3), 301-307.
- Moss, M. L. (1968). A theoretical analysis of the functional matrix. Acta Biotheoretica, 18(1), 195-202.
- Stevens, K. A. (2006). Binocular vision in theropod dinosaurs. Journal of Vertebrate Paleontology, 26(2), 321-330.
December 28, 2014
Here are three fun things to do with Aquilops, in descending order of how much gear they require.
1. Print your own Aquilops fossil.
Got access to a 3D printer? Download the 3D models of the holotype skull, OMNH 34557, that we published as supplementary info with the paper, and rock out. Here’s a test print that the guys in our scientific visualization center made for me. I gotta tell you, after 18 and a half years of sauropods, it’s very satisfying to have a holotype I can shove in my pocket. UPDATE a few weeks later: read Zach Miller’s post about his 3D-printed Aquilops holotype, it’s cool.
Want a bigger challenge? If you printed it in steel or titanium, it would probably make a decent bottle opener. Just sayin’.
Got access to a regular printer? Download these files, print, cut, fold, and enjoy:
Aquilops cut-and-fold – 2 small skulls. Should print 2 skulls at about life size on regular 8.5 x 11 or A4 paper. Warning: they’re small.
Aquilops cut-and-fold – 1 large skull. Warning: still not very big.
I found that regular printer paper is too flimsy to really hold the shape, so I built mine an endoskeleton (endoskull?) out of bits of cut up file folder. Just about anything would work. Teaching a course in which Aquilops could be relevant (which is all of them)? Have your students roll their own paper skulls, and use them as a springboard for talking about dinosaurs or evolution or anatomy or current events or whatever tickles your fancy.
Want a bigger challenge? My cut-and-fold skull is the epitome of laziness: I just mirror-image duplicated my lateral view and sandwiched the dorsal view in between. You could definitely make a better one, and with all of the free Aquilops data online, you have all the raw material you need. If you come up with something good, let me know in the comments and I’ll feature it in a later post.
3. Play with the 3D models.
No access to a printer of any sort? Well, you can still have fun with Aquilops in your browser and on your hard drive. If you want to see the holotype specimen as it looks today, there are 3D PDFs in the paper’s supplementary info. But if you haven’t been to the OMNH Aquilops page to play with the model of the complete, uncrushed skull that Garrett Stowe made, go do that now. On the same page is a 3D life restoration of Aquilops, also by Garrett Stowe. Both models are awesome, and Garrett is still working on them so they’ll be even better soon.
Want a bigger challenge? Surprise me. We made Aquilops freely available to the world, so you can take any and all of the stuff that we published – the figures from the paper, Brian Engh’s artwork, the 3D models of the fossil – and make cool new things that we haven’t thought of. C’mon, let’s play.
December 18, 2014
A friend’s daughter owned a pet corn snake, and a hamster. About a month ago, the former got into the latter’s cage — and in a reversal of the usual course of such events, sustained some nasty injuries. As snakes often do, it struggled to recover, and the wound seems to have necrotised.
This morning I got an email from the friend saying that the snake had died, and asking whether I would like it. I managed to restrain my enthusiasm for long enough to express condolences to the daughter; and an hour later, the snake was delivered!
Here it is — as with all these images, click through for the full resolution. I’ve learned that it’s difficult to measure the length of a snake — they don’t lay out straight in the way that you’d like, even when they’re dead — but as best I can make out, it’s 120 cm long. It weighs 225 g, but don’t tell Fiona I used the kitchen scales.
The hamster wound is very apparent, just behind the neck, on the left hand side. Here’s the head and neck in close-up:
Ouch — very nasty. It can’t have been pleasant watching a pet linger on with a wound like that.
He (or she? How do you sex a snake?) was a handsome beast, too. Here’s the head. You can easily make out the individual large scales covering it, and make out some of the shape of the skull.
The skulls of snakes are beyond weird. Here is one from an unspecified non-venomous snake at Skulls Unlimited (i.e. probably not a corn snake):
Hopefully at some point I’ll be able to show you my own snake’s skull. In the mean time, this guy says he has a corn-snake skull, but the photography’s not very good.
Finally, here is my snake, mouth open, showing the pterygoid teeth on the roof of the mouth:
What next? It seems clear that bugging is the only realistic way to free up the skeleton, and this may be the specimen that persuades me to invest in a proper colony of dermestids rather than just relying on whatever inverts happen to wander past.
It might be worth trying to skin and gut the snake first. Gutting will be easy; skinning might be very difficult. I think that removing the skin from the skull without damaging the very delicate bones might be impossible. Can dermestids cope with snake skin?
I’m taking advice!
December 12, 2014
If you’ve been reading around about Aquilops, you’ve probably seen it compared in size to a raven, a rabbit, or a cat. Where’d those comparisons come from? You’re about to find out.
Back in April I ran some numbers to get a rough idea of the size of Aquilops, both for my own interest and so we’d have some comparisons handy when the paper came out.
I started with the much more completely known Archaeoceratops. The measurements of Scott Hartman’s skeletal recon (shown above and on Scott’s website – thanks, Scott!) match the measurements of the Archaeo holotype given by Dodson and You (2003) almost perfectly. The total length of Archaeoceratops, including tail, is almost exactly one meter. Using graphic double integration, I got a volume of 8.88L total for a 1m Archaeoceratops. That would come down to 8.0L if the lungs occupied 10% of body volume, which is pretty standard for non-birds. So that’s about 17-18 lbs.
Archaeoceratops has a rostrum-jugal length of 145mm, compared to 84mm in Aquilops. Making the conservative assumption that Aquilops = Archaeoceratops*0.58, I got a body length of 60cm (about two feet), and volumes of 1.73 and 1.56 liters with and without lungs, or about 3.5 lbs in life. The internet informed me that the common raven, Corvus corax, has an adult length of 56-78 cm and a body mass of 0.7-2 kg. So, based on this admittedly tall and teetering tower of assumptions, handwaving, and wild guesses, Aquilops (the holotype individual, anyway) was about the size of a raven, in both length and mass. But ravens, although certainly well-known, are maybe a bit remote from the experience of a lot of people, so we wanted a comparison animal that more people would be familiar with. The estimated length and mass of the holotype individual of Aquilops also nicely overlap the species averages (60 cm, 1.4-2.7 kg) for the black-tailed jackrabbit, Lepus californicus, and they’re pretty close to lots of other rabbits as well, hence the comparison to bunnies.
Of course, ontogeny complicates things. Aquilops has some juvenile characters, like the big round orbit, but it doesn’t look like a hatchling. Our best guess is that it is neither a baby nor fully grown, but probably an older juvenile or young subadult. A full-grown Aquilops might have been somewhat larger, but almost certainly no larger than Archaeoceratops, and probably a meter or less in total length. So, about the size of a big housecat. That’s still pretty darned small for a non-avian dinosaur.
Although Aquilops represents everything I normally stand against – ornithischians, microvertebrates, heads – I confess that I have a sneaking affection for our wee beastie. Somebody’s just gotta make a little plush Aquilops, right? When and if that happens, you know where to find me.
- Dodson, P., and You, H.L. 2003. Redescription of neoceratopsian dinosaur Archaeoceratops and early evolution of Neoceratopsia. Acta Palaeontologica Polonica 48(2): 261-272.
- Farke, A.A., Maxwell, W.D., Cifelli, R.L., and Wedel, M.J. 2014. A ceratopsian dinosaur from the Lower Cretaceous of Western North America, and the biogeography of Neoceratopsia. PLoS ONE 9(12): e112055. doi:10.1371/journal.pone.0112055
December 11, 2014
As I mentioned in my first post on Aquilops, I drew the skull reconstructions that appear in figure 6 of the paper (Farke et al. 2014). I’m writing this post to explain that process.
We’ve blogged here before about the back-and-forth between paleontologists and artists when it comes to reconstructing and restoring extinct animals (example 1, example 2). Until now, I’ve always been the guy making suggestions about the art, and asking for changes. But for the Aquilops project, the shoe was on the other foot: Andy Farke was my ‘client’, and he had to coach me through drawing a basal ceratopsian skull – a subject that I was definitely not familiar with.
I started from the specimen, OMNH 34557, which is more complete than you might think at first glance. The skull is folded over about 2/3 of the way up the right orbit, so in lateral view it looks like the top of the orbit and the skull roof are missing. They’re actually present, just bent at such a sharp angle that they’re hard to see at the same time as the lateral side of the skull.
I also used a cast skull of Archaeoceratops as a reference – it’s clear from what we have of Aquilops that the two animals were pretty similar.
I started with this pencil outline on a piece of tracing paper.
And then I went right ahead and stippled the whole thing, without showing it to Andy until I was done. Yes, that was dumb. Noe the lack of sutures in this version.
I added sutures and sent it off to Andy, who sent it back with these suggested changes. At this point I realized my error: I had already spent about a day and a half putting ink on the page, and I’d have to either start all over, or do a lot of editing in GIMP. I picked the latter course, since there were plenty of areas that were salvageable.
Next I did something that I’d never done before, which is to redraw parts of the image and then composite them with the original in GIMP. Here’s are the redrawn bits.
With those bits composited in, and a few more tweaks to sutures, we got to this version, which was included in the submitted manuscript.
Then we brought Brian Engh in to do the life restorations. When Brian takes on a project, he does his homework. If you’ve seen his post on painting Aquilops, you know that all of the ferns in the Cloverly scene are based on actual fossils from the Cloverly Formation. Brian came to Claremont this summer and he and Andy and I spent most of a day at the Alf Museum looking at the specimen and talking about possible layouts for the full-body life restorations. He took a bunch of photos of the specimen while he was there, and a day or two later he sent us this diagram. He’d chopped up his photos of the skull to produce his own undistorted version to guide his painting, and in doing so he’d noticed that I had the line of the upper jaw a bit off.
That required another round of digital revisions to fix. It ended up being a lot more work than the earlier round of edits in GIMP, because so many features of the skull had to be adjusted. I ended up cutting my own skull recon into about 8 pieces and then stitching them back together one by one. Here’s what the image looked like about halfway through that process. The back of the skull, orbit, and beak are all fixed here, but the snout, cheek, and maxilla don’t yet fit together.
After a little more work, I got the whole thing back together, and this is the final version that appears in the paper. It is not perfect – the area in front of the orbit where the frontal, nasal, maxilla, and premaxilla come together is a bit dodgy, and I’m not totally happy with the postorbital. But eventually you have to stop revising and ship something, and this is what I shipped.
I did the dorsal view after the submitted version of the lateral view was finished. It went a lot faster, for several reasons:
- Most of the gross proportional issues were already sorted out from doing the lateral view first.
- The bilateral symmetry didn’t cut down on the number of dots but it did cut the conceptual workload in half.
- I did all my roughs in pencil and didn’t start inking until after we had almost all of the details hashed out.
I did have to revise the dorsal view after getting feedback from Brian about the lateral view, but that revision was pretty minor by comparison. I stretched the postorbital region and tinkered a bit with the face and the frill, and both of those steps required putting in some new dots, but it was still just one afternoon’s worth of work. Here’s the final dorsal recon:
In addition to the Life Lessons already noted in this post, I learned (or rather relearned) this important principle: if you do a big drawing and then shrink it down to column width, fine errors – a shaky line here, an ugly dot there – get pushed down below the threshold of perception. But there’s a cost, too, which is that uneven stippling becomes more apparent. I was skipping back and forth a lot between 25% image scale to see where the problem areas were, and 200% to revise the lines and dots accordingly.
All in all, it was a fun project. It was my most ambitious technical illustration to date, I learned a ton about ceratopsian skulls, and it was nice to get to make at least one substantial contribution to the paper.
Now, here’s the take-away: this is my reconstruction, and both of those words are important. “Reconstruction” because it has a lot of extrapolation, inference, and sheer guesswork included. “My” because you’re getting just one possible take on this. You can download the 3D files for the cranium and play with them yourselves. I hope that other artists and scientists will use those tools to produce their own reconstructions, and I fully expect that those reconstructions will differ from mine. I look forward to seeing them, and learning from them.
For other posts about my stippled technical illustrations, see:
Farke, A.A., Maxwell, W.D., Cifelli, R.L., and Wedel, M.J. 2014. A ceratopsian dinosaur from the Lower Cretaceous of Western North America, and the biogeography of Neoceratopsia. PLoS ONE 9(12): e112055. doi:10.1371/journal.pone.0112055
December 10, 2014
Today sees the description of Aquilops americanus (“American eagle face”), a new basal neoceratopsian from the Cloverly Formation of Montana, by Andy Farke, Rich Cifelli, Des Maxwell, and myself, with life restorations by Brian Engh. The paper, which has just been published in PLOS ONE, is open access, so you can download it, read it, share it, repost it, remix it, and in general do any of the vast scope of activities allowed under a CC-BY license, as long as we’re credited. Here’s the link – have fun.
Obviously ceratopsians are much more Andy’s bailiwick than mine, and you should go read his intro post here. In fact, you may well be wondering what the heck a guy who normally works on huge sauropod vertebrae is doing on a paper about a tiny ceratopsian skull. The short, short version is that I’m here because I know people.
The slightly longer version is that OMNH 34557, the holotype partial skull of Aquilops, was discovered by Scott Madsen back in 1999, on one of the joint Cloverly expeditions that Rich and Des had going on at the time (update: read Scott’s account of the discovery here). That the OMNH had gotten a good ceratopsian skull out of Cloverly has been one of the worst-kept secrets in paleo. But for various complicated reasons, it was still unpublished when I got to Claremont in 2008. Meanwhile, Andy Farke was starting to really rock out on ceratopsians at around that time.
For the record, the light bulb did not immediately go off over my head. In fact, it took a little over a year for me to realize, “Hey, I know two people with a ceratopsian that needs describing, and I also know someone who would really like to head that up. I should put these folks together.” So I proposed it to Rich, Des, and Andy in the spring of 2010, and here we are. My role on the paper was basically social glue and go-fer. And I drew the skull reconstruction – more on that in the next post.
Anyway, it’s not my meager contribution that you should care about. I am fairly certain that, just as Brontomerus coasted to global fame on the strength of Paco Gasco’s dynamite life restoration, whatever attention Aquilops gets will be due in large part to Brian Engh’s detailed and thoughtful work in bringing it to life – Brian has a nice post about that here. I am very happy to report that the three pieces Brian did for us – the fleshed-out head that appears at the top of this post and as Figure 6C in the paper, the Cloverly environment scene with the marauding Gobiconodon, and the sketch of the woman holding an Aquilops - are also available to world under the CC-BY license. So have fun with those, too.
Finally, I need to thank a couple of people. Steve Henriksen, our Vice President for Research here at Western University of Health Sciences, provided funds to commission the art from Brian. And Gary Wisser in our scientific visualization center used his sweet optical scanner to generate the hi-res 3D model of the skull. That model is also freely available online, as supplementary information with the paper. So if you have access to a 3D printer, you can print your own Aquilops – for research, for teaching, or just for fun.
Next time: Aquilöps gets röck döts.
Farke, A.A., Maxwell, W.D., Cifelli, R.L., and Wedel, M.J. 2014. A ceratopsian dinosaur from the Lower Cretaceous of Western North America, and the biogeography of Neoceratopsia. PLoS ONE 9(12): e112055. doi:10.1371/journal.pone.0112055
November 14, 2014
So how did the YPM come to make such a monstrosity? What was it based on? Tune in next time for the surprising details!
I told him at the time that I’d soon get around to writing a post. But before I did, he wrote a post on this himself: Bully for Camarasaurus. And it’s excellent. Go and read it!
I don’t have a lot to add to what Ben has written, except regarding this:
What Marsh had instead [when restoring the skull for his 1891 “Brontosaurus” reconstruction] were a few fragmentary bits of Camarasaurus cranial material, plus a snout and jaw (USNM 5730) now considered to be Brachiosaurus.
Here’s what Marsh came up with:
But what of the supposed Brachiosaurus skull that he used as a reference? It was finally described 107 years later by Carpenter and Tidwell (1998), in a paper that helpfully also lays out the history behind it. Here’s how it looks:
The skull was found by a crew under the supervision of M. P. Felch in the western part of his Quarry 1, Garden Park, Colorado. Felch reported it to O. C. Marsh in a letter of 8 September 1883. It was found by a meter-long cervical vertebra that probably belonged to Brachiosaurus “which was destroyed during attempts to collect it” (McIntosh and Berman 1975:196). [Of course, Felch and Marsh could hardly have been expected to identify this vertebra correctly, as Brachiosaurus would not be discovered and named for another twenty years (Riggs 1903), and the nature of its neck would not become apparent until Janensch (1914) described the related brachiosaurid Giraffatitan (= “Brachiosaurus“) brancai.]
The Felch skull, along with other material from the quarry, was shipped to Marsh at Yale in October of that year, and was initially assigned the specimen number YPM 1986. At that time it was only partially prepared, hence the rather poor resemblance between the restored version above and Marsh’s hypothetical “Brontosaurus” [= Apatosaurus] skull that was based on it.
It’s notable that Holland (1915) was quite certain that this was not a skull of Brontosaurus, and that a Diplodocus-like skull found with the A. louisae holotype belonged to it. It’s worth reading the skull section of his paper to see just how solid his reasoning was. And it’s extraordinary to think that Osborn’s power, all the way over in New York, was so great that he was able to successfully bully Holland, 370 miles away in Pittsburgh, into not putting the evidently correct skull on the Carnegie Museum’s Apatosaurus mount. That mount remained sadly headless until after Holland’s death.
Aaanyway, YPM 1986 was pretty much ignored after Marsh’s abuse of it as a reference for the Brontosaurus reconstruction’s skull. After Marsh’s death in 1899, much of the material collected by Felch was transferred to the Smithsonian (US National Museum of Natural History). The skull was among these specimens, and so was re-catalogued as USNM 5730.
As so often, it was Jack McIntosh who rediscovered this skull and recognised its true affinities. Some time after his tentative identification of the skull as pertaining to Brachiosaurus (presumably on the basis of its resemblance to that of Giraffatitan), Carpenter borrowed the skull, had it more fully prepared, wrote the description, and had a restored model constructed from casts of the preserved elements and models of the missing ones.
Carpenter and Tidwell (1998:fig. 2) also handily showed the restored Felch quarry skull alongside those of other sauropods:
By re-ordering the top row, we can see what a neat intermediate it is between the skulls of Camarasaurus (left) and Giraffatitan (= “Brachiosaurus” of their usage):
I provisionally accepted USNM 5730 as belonging to Brachiosaurus in my re-evaluation of 2009, and included it in my reconstruction (Taylor 2009:fig. 7):
But as noted by Carpenter and Tidwell (1998:82), the lack of comparable parts between the Felch skull and the Brachiosaurus holotype (which remains the only definitive Brachiosaurus material) means that the assignment has to remain tentative.
What we really need is a more complete Brachiosaurus specimen: one with both a skull and good postcervical elements that let us refer it definitively to Brachiosaurus altithorax by comparison with the holotype. And heck, while we’re at it, let’s have a specimen with a good neck, too!
The real question remains: how did Marsh, using a brachiosaur skull as his basis, come up with this?
And stranger still, how someone at the Yale Peabody Museum — we don’t know who — used it, or more likely Marsh’s reconstruction, as a basis for this sculpture:
The Yale mount didn’t go up until 1931 — the last of the Big Four Apatosaurus mounts after the AMNH, Carnegie and Field Museum, which is surprising as it was the first of those specimens to be found. So by the time the skull was sculpted, sauropod skulls were actually reasonably well known. It’s not clear quite how anyone working from a decent reconstruction of, say, a Camarasaurus skull — the one in Osborn and Mook (1921:figure 30), say — could come up with this monster.
The last thing to say is this: it does credit to the YPM that they display this historically important sculpture rather than hiding it away and pretending it never happened. For me, part of the fascination of palaeontology is seeing not just how organisms evolved through prehistory but how ideas evolved through history. It’s great that we can still see important mistakes, alongside their corrections (i.e. the new and lovely skull on the YPM Apatosaurus mount.)
- Carpenter, Kenneth, and Virginia Tidwell. 1998. Preliminary description of a Brachiosaurus skull from Felch Quarry 1, Garden Park, Colorado. Modern Geology 23:69-84.
- Holland, William J. 1915. Heads and tails: a few notes relating to the structure of the sauropod dinosaurs. Annals of the Carnegie Museum 9:273-278.
- Janensch, Werner. 1914. Ubersicht uber der Wirbeltierfauna der Tendaguru-Schichten nebst einer kurzen Charakterisierung der neu aufgefuhrten Arten von Sauropoden. Archiv fur Biontologie, Berlin III, 1(1):81-110.
- Marsh, O. C. 1891. Restoration of Triceratops (with plates XV and XVI). American Journal of Science, 3rd series 41(244):339-342.
- McIntosh, John S., and David, S. Berman. 1975. Description of the palate and lower jaw of the sauropod dinosaur Diplodocus (Reptilia: Saurischia) with remarks on the nature of the skull of Apatosaurus. Journal of Paleontology 49(1):187-199.
- 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.
- Riggs, Elmer S. 1903. Brachiosaurus altithorax, the largest known dinosaur. American Journal of Science 15(4):299-306.
- Taylor, Michael P. 2009. A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from Giraffatitan brancai (Janensch 1914). Journal of Vertebrate Paleontology 29(3):787-806.