September 22, 2016
Judgmental readers will recall that I have dabbled in mammal skulls, thanks to the corrupting influence of my friend and colleague, Brian Kraatz. At the end of my last post on this sordid topic, I mentioned that Brian and Emma Sherratt were working on a version 2.0 based in 3D morphometrics. The first volley from that project was published today in PeerJ.
Happily for all of us, Brian and Em confirmed the relationship between facial tilt and locomotor mode that we first documented last year, using more taxa, more landmarks, and two more dimensions (Kraatz and Sherratt 2016: 12):
…in accordance with previous findings by Kraatz et al. (2015), facial tilt angle is correlated with locomotor mode (D-PGLS, F(2,17) = 11.13, P = 0.003), where lower facial tilt angle, meaning more pronounced cranial flexion, is found in cursorial species, and high angles are found in generalist species.
That’s just the most personally relevant tip of a very large, multifaceted iceberg, including a monster supplementary info package on FigShare with, among other things, 3D models of bunny skulls. It’s all free and awesome, so go have fun.
May 6, 2016
Today, we were at the BYU Museum of Paleontology, which is in a ridiculously scenic setting with snow-capped mountains on the horizon in almost every direction.
We got through a lot of good work in collections, and we’ll show you some photos from there in due course. But for today, here are a couple of pictures from the public galleries.
First, here in a single photo is definitive proof that the “Toroceratops hypothesis” is wrong:
Say what you want about ontegenetic trajectories, that huge and well ossified Triceratops is not a juvenile of anything.
Good, glad we go that sorted out.
Meanwhile, at the even better end of the gallery, here is a very nice — and very well lit — cast of the famous articulated juvenile Camarasaurus specimen CM 11338 described by Gilmore (1925):
Further bulletins as events warrant.
Gilmore, Charles W. 1925. A nearly complete articulated skeleton of
Camarasaurus, a saurischian dinosaur from the Dinosaur National
Monument, Utah. Memoirs of the Carnegie Museum 10:347-384.
April 28, 2016
Yesterday we got a treat: the description of a new titanosaur, Sarmientosaurus musacchioi, based on some decent cervical vertebrae and an almost absurdly nice skull from the Upper Cretaceous of Argentina (Martinez et al., 2016). It was published in PLOS ONE so it’s free to the world, including a 3D PDF of the skull and some awesome visualizations. Get all that good stuff here.
I had one day’s warning about this – Brian Switek contacted me on Monday to ask if I’d be willing to lend my thoughts on the new critter for his news article for National Geographic, which you can read here. As always, I sent more stuff than he could use, so I’m recycling the long form for the rest of this post.
Brian’s first question was about how Sarmientosaurus stands out. I wrote:
Sarmientosaurus has probably the most complete and best-preserved skull of any sauropod from South America to date. It’s kind of funny – for so long we had so few good skulls from brachiosaurs and titanosaurs, and now we’re getting them, but without much of the rest of the skeleton. In North America, unquestionably the nicest Cretaceous sauropod skull is that of the brachiosaurid Abydosaurus, but all we have with the skull is a bit of the neck. Same situation now with this new titanosaur, Sarmientosaurus. I’m not complaining – great skulls without bodies are still great skulls! – but it will be nice to someday connect heads and bodies.
Also, the authors are to be commended – I don’t think anyone has ever done such a thorough job describing the skull of a sauropod dinosaur. This paper will become the standard to which all others are compared going forward.
I stand by all of that. This new paper is just ridiculous in quantity and quality of descriptive detail. Do you like technicolor sauropod palates? Here, have a technicolor sauropod palate:
The next question from Brian was about the head posture and the inference drawn by Martinez et al. (2016) that Sarmientosaurus fed at ground level. My take:
It doesn’t seem unlikely to me that Sarmientosaurus had a downward-facing snout. As for being a low grazer, I am skeptical. The inner ear usually tells us something about the alert posture of an animal, not its feeding posture. Take rhinos – some of them graze from the ground, and some of them browse up higher, but they all carry their heads the same way. Most grazers have wide snouts, whereas that of Sarmientosaurus is pointed and even a little narrower than that of Giraffatitan. That’s a curious shape for a supposed grazer.
So there are three points to unpack here. First, I chose my words deliberately in saying that the inner ear tells us “something” about the alert posture, because in fact the horizontal semicircular canals (HSCCs) aren’t great even at that. As I wrote in this post seven years ago:
Where SCCs have really attracted attention in paleontology is the “more or less” horizontal orientation of the HSCCs in living animals. Some authors have argued that if you set the HSCCs level or close to level, you can figure out how the head was oriented in life.
Well, maybe. The problem is that there is a LOT of variation around level. In birds surveyed by Duijm (1951), HSCC orientation varied by 50 degrees among taxa, from 20 degrees below horizontal to 30 degrees above. Furthermore, in humans HSCC orientation varies by up to 20 degrees among individuals. Possibly humans are weirdly variable, but it seems at least equally likely that most critters are and we’ve only discovered that variation in humans because of the huge sample size.
However you slice it, those are darn big error bars around any given head posture. That doesn’t mean that HSCC orientations in dinosaurs and other extinct vertebrates are worthless for determining posture (they may also be a source of taxonomic information). Strictly speaking, it means that preserved HSCCs can get us in the 50-degree ballpark but can’t narrow things down any further. This is one of those areas in paleontology where we’re just going to have to live with a certain amount of uncertainty, at least for now.
As far as I know, that’s all still true. But I’d love to be wrong.
Second, there’s the difference between alert posture and feeding posture. Go watch horses graze – the skull is practically vertical while they’re feeding, but that’s not the orientation you get from the HSCCs. So if I’m skeptical about ignoring the error bars around HSCC orientation to determine alert posture, I’m even more skeptical about trying to infer feeding posture from them. Also, the rhino point – we have an extant group with closely related taxa where one is a grazer (white rhino, Ceratotherium) and one is a browser (black rhino, Diceros). They hold their heads about the same. So feeding preference will not necessarily be reflected in normal, non-feeding head posture.Third, muzzle shape. Most grazers have wide mouths, but as I said in the email to Brian – and as this figure shows – the snout of Sarmientosaurus is narrower than that of Giraffatitan, and I don’t think anyone is seriously proposing that Giraffatitan was a grazer. So if Sarmientosaurus was more committed to low-level feeding than more basal titanosauriforms, its face was evolving in the wrong direction. Just sayin’.
(Incidentally, I am hugely in favor of figures like 33 and 34 in Martinez et al., 2016, which make it easy to compare the new critter to a selection of reference taxa. I wish everyone would do this all the time.)Finally (final for the purposes of the interview), Brian noted that in the media sauropods are often depicted as all being pretty much the same, and he asked what made Sarmientosaurus stand out. My response:
Until now, the skulls we’ve found of basal titanosauriforms – brachiosaurs and relatives – and more derived titanosaurs haven’t looked much alike. To me Sarmientosaurus is cool because it bridges that gap. From the top and the front the skull looks a lot like those of Brachiosaurus and Giraffatitan – really wide, pretty big teeth, long toothrow. But from the side, the smaller nostrils and long snout have obvious similarities to more derived titanosaurs like Nemegtosaurus. And they phylogenetic analysis confirms that, which is nice. But you can take one look at this thing and say, “Yeah, cool, we’ve been waiting for someone like you.”
The lateral views of titanosauriform skulls in the above figure nicely illustrate my point. If you took the Giraffatitan skull in A and the Tapuiasaurus skull in F and did a 50% morph between them, you’d get something pretty darned close to Sarmientosaurus. And about halfway between Giraffatitan and the really derived saltasaurids is where the phylogenetic analysis puts Sarmientosaurus. The gestalt of the skull nicely reflects the animal’s relationships, which does not always happen.
Oh, there are cervical vertebrae, too, and a seriously weird ossified tendon that is apparently not a cervical rib, but those will keep for another post.
The take-home here is that although I disagree with the authors on a few points of paleobiological interpretation, the Sarmientosaurus fossils are spectacular and Martinez et al. (2016) have done a tremendous job of describing and illustrating them. And the paper is free to anyone who wants it, as it should be. One of the great delights of the last few years has been watching PLOS ONE and PeerJ become the preferred outlets for high-quality descriptive work on dinosaurs.
Now if we can just find more of this thing!
Martínez RDF, Lamanna MC, Novas FE, Ridgely RC, Casal GA, Martínez JE, et al. (2016) A Basal Lithostrotian Titanosaur (Dinosauria: Sauropoda) with a Complete Skull: Implications for the Evolution and Paleobiology of Titanosauria. PLoS ONE 11(4): e0151661. doi:10.1371/journal.pone.0151661
Several drinks later, they all die and somehow become skeletonised, and that’s how they all land up on a table in my office:
Top left: pieces of monitor lizard Varanus exanthematicus. Cervical vertebrae 1-7 on the piece of paper, femora visible above them, bits of feet below them. Awaiting reassembly. The whole skeleton is there.
Top right, on a plate on top of some lizard bits: skull, cervicals and feet of common pheasant Phasianus colchicus. The skull has come apart, and I can’t figure out how to reattach the quadrates. One of the feet is cleanly prepped out and waiting to be reassembled, while the other retains some skin for now.
Bottom left: skull and anterior cervicals of red fox Vulpes vulpes. Lots of teeth came out during the defleshing process, and will need to be carefully relocated and glued after the skull has finished drying out.
Bottom right: skull and anterior cervicals of European badger Meles meles. The skull is flat-out awesome, and by far my favourite among my mammal skulls. If tyrannosaurs were medium-sized fossorial mammals, they’d have badgers’ skulls for sure. A few teeth that came out have been glued into place; once the glue is dry, this skull is done.
April 2, 2016
I wanted to do a three-way comparison between my carnivoran skulls, but I’m too impatient to wait till I’ve got the fox’s skull out of its head. So here are the two I have now: the badger (left) and the cat (right):
(Both skulls appear with their first three cervicals.)
As you can see, the badger is more impressive in every way. It’s physically bigger of course, but also much more robust, as most easily seen in the zygomatic arches and the fully fused skull. Also relevant is the huge sagittal crest, which you will recall anchored hugely oversized jaw-muscles. In comparison, the cat’s jaw muscles were like those of pussy-cats.
It’s like the difference between a tyrannosaur and an allosaur.
You can see the crest more clearly — and general robustitude — in anterodorsolateral view:
We really do underestimate what awesome animals badgers are. One of the many reasons I would never participate in a badger cull is simple, straightforward fear.
Do not meddle in the affairs of badgers, for they are unsubtle and quick to bite your arm off.
March 28, 2016
There’s no sense in decapitating a badger if you’re not going to make good use of the severed head. So here’s what I did with mine. First, a reminder of the state it was in after yesterday’s adventures:
Ideally, I would have liked to skin the head — it would have made subsequent stages easier and less messy. But as I noted last time, badgers have very tough skin, and it was hard to do anything with it. I feared that the force necessary would at best damage the underlying bone, and at worse give me a nasty cut.
So I satisfied myself with trimming away the flesh collar, leaving the head-and-anterior-neck segment a little shorter, and of a suitable size to go into the saucepan:
Then it was a simple matter of filling with hot water …
… then bringing it all up to a simmer, and giving it a couple of hours while I played some Skyrim and watched an episode of Elementary. Once I’d drained the water off, here’s the result of the first simmer:
As you can see (you may need to click through to make it out properly), that tough skin has contracted so hard that it’s pulled away from the skull at the top, exposing part of the distinctive midline crest.
Anyone, with the skin now softened it was relatively easy (though disgusting) to peel it off. Once all the rest of the superficial soft-tissue was gone, the massive massive muscles that attached to the midline crest were apparent.
I broke these off:
You can see one of them in the last photo. It really is a substantial piece of equipment: and you can see as well that the muscle mass going through the zygomatic arches is substantial.
You may also notice that at this stage, I’ve left the nose intact. That’s because I didn’t want to risk damaging the delicate nasal turbinates by pulling the soft-tissue away too roughly. Instead, I left it on for the second simmer:
As you can see, it came out from that with the meat much more cooked, and so easier to remove:
In my previous adventures preparing mammal skulls, I’ve found that one of the most satisfying moments is when the mandible (lower jaw) comes away from the cranium. You really feel that you’re making progress then, and it becomes much easier to reach some of the tricker areas of soft-tissue. That doesn’t happen with badgers: they jaws are permanently articulated, with cylindrical articular condyles wrapped in incomplete bone-tunnels. (I hope I can show you this properly one preparation is complete.)
Anyway, I was able to do a much better job of removing the meat this time: only scraps are left, and I was also at this point able to remove and begin cleaning the first few cervical vertebrae. I have the atlas, axis and damaged third. (I discarded the last of these, since it’s not complete.) Here’s the state of it at this point:
And that skull in right lateral view, hopefully dispelling any remaining misconceptions you may have had about badgers being cute:
As you can see, there were still plenty of scraps of hard-to-remove flesh clinging on, especially around the jaws and the base of the cranium. So it was time for simmer number three. I will spare you yet more photos of my saucepan, and instead skip straight to the skull as it appeared after this phase, and after I’d remove more of the flesh. Much nicer:
You may be wondering, what is the best way to clean the teeth of a dead and partially prepared badger skull? Sometimes the obvious answer is the right one, and this is one of those occasions. A toothbrush is the tool of choice, and it works wonders with the base of the cranium, too. (Warning: do not allow the toothbrush to re-enter civilian society after this experience.)
Here we have the skull with the mandible open:
Do not get bitten by a badger.
Skull in dorsal view:
One of the many things that’s impressed me about this badger is how very much meat there was on its skull. I kept it, or most of it, and now you have the privilege of seeing the skull and its soft-tissue together:
This is dramatically different from how we think of heads, or at least of how I do. I think this is because when we hear “skull”, we’ve been conditioned by years of Scooby Doo and Indiana Jones to think “human skull”. And I think that human heads much more closely match the profile of their skulls than those of badgers do theirs.
Of course this is just another way of saying that there is a lot more muscle on a badger skull, which is another way of saying that this is a seriously powerful animal. I know I keep making this point, but I think it’s a point well worth making. The world has had quite enough of this kind of thing (from here):
And its time that we all started to give badgers the credit they deserve. They are basically small bears with misleadingly endearing facial coloration.
(BTW., when I say that I kept the meat, I mean that I kept it until I’d taken that photo. Then I threw it away. I’ve not kept it permanently, I’m not a sicko. No, I’m not.)
I leave you with one of the less successful old music-hall jokes:
- First man: I say, I say I say! What’s the best way to remove the brain from a dead and partially cooked badger skull?
- Second man: Actually, there is no good way. The best I’ve found is to shove a chopstick through the foramen magnum, swirl it around to break up the tissue, then shake the bits out and repeatedly rinse.
- First man: That’s disgusting.
- Second man: I never said it wasn’t.
Here is the residue, in our sink:
Fiona, if you’re reading this: I promise I will have this all nicely cleaned up before you return from your parents’ house with the boys.
(Did I mention that Fiona had taken the boys to her parents’ house? It’s not because of the dead badger. It’s just coincidence. I think.)
Over the last couple of weeks, I’ve been fortunate enough to acquire two medium-sized native mammals, both roadkill specimens in good conditions: a fox and a badger:
But I’ve found from bitter experience that prepping out the entire skeleton of good-sized animals like these is a lot of dirty smelly work. So I decided to make things easier on myself by only prepping the skulls of these two.
Step one: remove the heads.
What follows is not pretty. Parental advisory: you should avoid this post if you feel a misguided sentimentality about the already-dead corpses of deceased animals.
I considered several approaches, as recommended by commenters on this blog and people on Twitter, but ended up taking the butcher’s approach — mostly because I have a good, sharp knife, but lack some of the tools needed for other approaches.
I took on the fox first. I cut through the skin surrounding its neck, and peeled it back far enough to reveal the neck musculature:
From there, it was pretty easy to slice away the muscles down towards the vertebrae — but impossible to get right to the vertebrae themselves, because they’re surrounded by gloop including not only muscles, but ligaments, fascia and tendons:
I’d hoped to be able to feel my way to an intervertebral joint, and ease it apart with the knife. But that turned out to be difficult. It was also going to need a lot of force, and I was worried that down in among all that gloop, I might slip and cut myself.
So I used our the axe we use for chopping firewood. It would have been terrible for dealing with the flesh, but it was fine for the bones:
Then it was the same procedure for the badger. I started by cutting a ring around the skin of the neck and peeling back.
Straight away, it was obvious that the badger is a much more serious piece of kit than the fox. It’s not as long, but it’s heavier, and much more muscular, and it has way tougher skin. I don’t know if foxes and badgers ever fight, but if they do, my money is on the badger every time. It would bite much harder and its claws are epic, too. The only thing the fox would be better at is running away.
Then, as with the fox, I sliced away the meat till I reached the bony core of the neck:
And again, the axe finished the job. I was left with a pair of decapitated corpses:
And, more importantly, a pair of heads:
Also, some evidence of my activities in the bloodstained chopping block. I hope the neighbours don’t see this and leap to the wrong conclusion:
What to do with the sadly unloved postcrania? I have no further use for them, so I decided to bury the bodies. I went down to the bottom of our garden, only to find all the sheep in the adjacent field coming over to see what I was doing:
Best stay back, sheep! Or you could be next!
I dug a hole, which is a lot more work than it looks. Predictably, given than I am England during what passes for springtime, it suddenly stared hailing while I was digging. But eventually, I was done:
In went the postcranial pair:
And pretty soon, you’d never have known anything had happened here.
Next time: exciting adventures with the badger head!