Get your red-cyan glasses — you do have some, right? — and check out this glorious image. Best full-screen it, it’s worth seeing!

And here is the lame 2D version for those of you who have still not spent 99 lousy cents on a pair of 3D glasses:

What are we looking at here?

Well, the smaller skull at bottom left is my new badger, which we saw a couple of days ago. Since then it has dried out, and I was easily able to figure out which teeth belong where, and glue them in with a drop of wood glue. I’ll photograph it in more detail at some point, but for those of you who can’t wait, there’s always the TNF of my first badger skull.

On the right is, if I’m not mistaken, a sheep — specifically a ram, given the horns. I don’t actually remember this one’s origin story, but it’s been sitting on a box next to our oil tank for a couple of years, with the flesh bits slowly decaying off and the bone cleaning itself up the way nature intended. A couple of days ago I cleaned it up a bit with my trusty toothbrush to remove some bits of moss and lichen, then soaked it for a few hours in very dilute bleach. It’s dried out beautifully, and is very robust. It’s big, too.

Everything else you see belongs to a deer — I assume, based on the horn bases. This is another one recovered from the depths of time. Some years ago, I put it a big water-filled pan and left it outside and forgot about it. In that time, not only had all the meat rotted off the bones, but the water had clarified and everything in it had died, so it didn’t even smell particularly. When I took the bones out, they were a nasty brown colour and little soft, and I thought I was going to have to discard them all. But once they had dried out they seemed a little more robust — though still brown. Then I left them overnight in dilute bleach, and when they had dried from that, they were their present much more appealing whitish colour, so I think they’re going to be OK.

Most of the cranium is intact in a single piece, though some of the sutures are wobbly and will need stabilising with wood glue. The mandible is in two parts, but both seem in decent condition. Right at the bottom left of the photo is a shard of bone by the tip of the mandible: this is the left nasal, which flaked off, but should be repairable. Everything else is vertebrae: atlas right behind the skull, axis by the snout, C3 just above it, and damaged C4 just below the atlas.

When it’s been put together a bit more, I will post some better photos, and I’ll see if anyone can identify the species.

Last week, while Fiona and I were out walking, we noticed a decaying roadkill badger a bit over half a mile from our house. Yesterday we were out walking again, and we saw that it had decayed to the point where there was not much to the flesh at all. I prodded it with my foot and found that the skull was about ready to come away.

So when we got home, I popped straight back out in the car with some plastic bags which I used as improvised gloves, found the badger, managed to pull its head away from the remaining connective tissue (not a pleasant process) and bring it home. I simmered it gently for a couple of hours — outdoors on a portable hob, I’m not a barbarian — then cleaned it with a toothbrush left it to cool. Today I soaked it in a soapy water for a couple of hours, then rinsed it off and soaked it in very diluted bleach for a couple more, taking care to harvest all the loose teeth that came out during each stage. Finally I rinsed it off, and here it!

European badger Meles meles, skull in left lateral view, with teeth. Pound coin for scale.

What next? I’ll give it couple of days to dry properly, then figure out which teeth go in which sockets and glue them in place. Then, bam, I have a second badger skull to go with my first, and I’ll be in a position to directly compare two skulls of the same animal.

This is a really nice, quick process compared with most of my preparations. The trick is to find a carcass that has already gone through the nastier stages of decomposition.

Note that the jaw is articulated, by the way. Unlike most animals, the skull of the badger locks the jaw in place with unusual joints in which the mandibular fossa of the cranium wraps around the cylindrical articular condyles of the jaw. I’ll try to include photos next time.

I leave you with a cheap-and-cheerful 3D anaglyph of the skull. Did I ever mention that you should get some cheap 3D glasses? You should get some cheap 3D glasses.

For reasons that I will explain in a later post, I am parting with one of my most treasured possessions: the badger skull that I extracted from my roadkill specimen four years ago.

As a farewell, I finally photographed it properly from all the cardinal directions, and prepared this multiview:

Don’t forget to click though for the full resolution version!

The new monster redescription of Dilophosaurus by Adam Marsh and Tim Rowe came out in the Journal of Paleontology last week. I’m blogging about it now because the OA link just went live yesterday. So you can get this huge, important paper for free, at this link.

There’s a lot of stuff to love here: beautiful, clear photos of every element from every specimen from multiple angles, interesting anatomical and phylogenetic findings, and of particular interest on this blog, some very cool documentation of serial variation in pneumatic features. Here in Figure 62 we see serial changes in the posterior centrodiapophyseal laminae, which in some of the vertebrae are split around an intermediate fossa, or have accessory laminae.

One thing that I’ve thought a lot about, but written not so much about (yet), is pneumatic features on the ventral surfaces of vertebrae and how they change along the column. So I was excited to see Figure 64, which shows how fossae change serially on both the lateral and the ventral surfaces of the presacral centra. As far as I know, no-one has ever done something like this for a sauropod (please correct me in the comments if I’ve forgotten any examples), but it could be done and the results would be interesting, particularly for taxa like Haplocanthosaurus or Dicraeosaurus that have both lateral and ventral fossae and keels in at least some of the vertebrae.

Here’s Figure 66, a beautiful new skull reconstruction and life restoration, both by Brian Engh. There’s a lot of Engh/Dilophosaurus stuff going on right now, including a new video for the St. George Dinosaur Discovery Site museum (short version here, longer version available at the museum, and I think on Brian’s Patreon page), and, uh, another thing that will be revealed in the not-too-distant future.

I hope everyone is well and safe. When I first realized we were going into quarantine back in March, I had big plans for doing various series of posts here, but almost immediately the demand of getting med school anatomy online ate up all my time and creative energy. Just barely getting back on my feet now. I know Mike has been busier than normal, too. So please be patient with us, and we’ll try to remember to feed the blog now and then.

Reference

Marsh, Adam D., and Rowe, Timothy B. 2020. A comprehensive anatomical and phylogenetic evaluation of Dilophosaurus wetherilli (Dinosauria, Theropoda) with descriptions of new specimens from the Kayenta Formation of northern Arizona. Journal of Paleontology Volume 94, Supplement S78: 1-103. DOI: https://doi.org/10.1017/jpa.2020.14

Heinrich Mallison sent me this amazing photo, which he found unattributed on Facebook:

Infuriatingly, I’ve not been able to track down an original source for this: searching for the text just finds a bunch of reposts on meme sites, and Google’s reverse image search just reports a bunch of hits on Reddit:

The line-drawing shows some scientific understanding of bird skeletons, so I imagine someone put real thought into this and is unhappy that the image is propagating uncredited. If that person reads this, please leave a comment: I’d love to credit it properly.

Anyway … what’s going on here?

Birds (like all vertebrates) have two tubes running down the ventral aspect of the neck (i.e. below the vertebrae): the trachea, for breathing, and the oesophagus, for swallowing. But these both open into the back of the mouth and are not piped up past it. I’ve not dissected enough bird heads to show this clearly, but when I was taking Veronica apart the trachea was pretty visibly ending in the mouth cavity, not plumbed up past the mouth into the nasal space:

So yes, I think it’s true: shoebills can bulge their spines out of their mouths.

Why? My best guess that there’s just nowhere else for the spine to go when the neck is retracted. There’s a big empty space in the mouth, why let it go to waste?

From Will’s Skull Page, here.

Here’s a skull of a wild boar. Note the loooong face, practically a straight line from the tip of the snout to the top of the back of the head.

We shall now proceed through a series of pig skulls with increasingly steep foreheads.

From the UCL Museums and Collections blog, here.

Some domestic pigs have a longish snout and nearly straight forehead, like their wild forebears. (Or foreboars, if you will.)

A cast skull from Carolina, available here.

But it seems–from a quick, unscientific, and in-no-way-standardized image search–that the vast majority of domestic pigs have at minimum a more steeply-inclined forehead.

This one was auctioned in New Zealand, at this site.

Foreheadization is becoming undeniable.

From skullbase.info, here.

Is this one any more pronounced than the one before? I’m not sure, and so far I’m too lazy to try superimposing the skulls. But they don’t even look like the same kind of animal as the wild boar shown at top.

From theweirdandwonderful.com, now apparently only available on Pinterest, here.

In my explorations so far, this appears to the ne plus ultra of short-faced, high-forehead domestic pigs, excluding truly pathological cases. The line from the inflection point of the forehead to the occiput is twice the length of the snout!

From theweirdandwonderful.com, now apparently only available on Pinterest, here.

Oddly enough, the high forehead in domestic pigs is not always associated with a super-short snout, as this skull demonstrates.

This figure from Owen et al. (2014) sums up the shape differences between domestic (left) and wild (right) Sus scrofa.

Okay, so domestic pigs have shorter snouts and steeper foreheads than wild pigs of the same species. But y tho? It seems to be part of the “domestication syndrome” present in many domesticated animals, which includes a shortened snout, smaller teeth, piebald coloration, floppy ears, a curly tail, and a host of other morphological and behavioral traits. Interestingly, pigs seem to show more aspects of domestication syndrome than any other domestic animals other than dogs, as shown in the figure below, from Sanchez-Villagra et al. (2016).

Okay, so domestication, but how? It’s not like the Domestication Fairy comes in the night and steals half your snout.

Wilkins et al. (2014: fig. 1)

The various morphological changes that go along with domestication syndrome seemed disconnected until 2014, when Wilkins et al. proposed a pretty nifty hypothesis, which goes like this:

  • Probably the most crucial aspect of domestication is selection for tameness, which is really selection for reduced adrenal gland and sympathetic nervous system activity, so the animals aren’t freaking out all the time.
  • The adrenal glands and sympathetic ganglia are derived from embryonic neural crest, which also influences the growth of the teeth, brain, skull, vertebral column, and ear cartilages, and the distribution of melanocytes in the skin and coat.
  • Selection for increased tameness (= reduced freaking out) is really selection for reduced neural crest activity in early development, and the smaller teeth, shorter snout, floppy ears, curly tail, patchy coloration, and so on, are unselected developmental consequences of reduced neural crest activity.

Wilkins et al. (2014: fig. 2)

So far, so good. The neural crest hypothesis seems to have genuine explanatory power, in that it lassos a disparate set of phenomena and provides a single, logical cause. Of course not everyone is convinced, and the neural crest hypothesis could be true without ruling out other complementary mechanisms and confounding effects. Along those lines, Sanchez-Villagra et al. (2016) is worth a read. It’s free at the link below, as is Wilkins et al. (2014).

The neural crest hypothesis might explain why domestic pigs have shorter snouts than their wild relatives, but I think there must be some other factors in play to explain pig foreheads. Which is fine, domestic dogs have a staggering variety of skull shapes that reflect thousands of years of strong artificial selection, and probably a healthy dose of unintended consequences and other knock-on effects. Given that pigs have been domesticated for a long time, were probably domesticated many times in many places, have had frequent infusions of wild-type genes (from possibly genetically disparate wild populations), and have been canalized into different breeds, it might actually be weirder if they all looked like short-snouted wild boars. All of which is a long way of saying that I’m not surprised that domestic pigs don’t all fall on some morphogenetic monocline from wild boars, but I’m still curious about how they got their foreheads.

I actually started writing this post before the very interesting discussion of pig domestication flared up in the comments on Mike’s pig skull post. Mike’s two skulls nicely illustrate the difference between forehead-less and, er, forehead-ful conditions, and the comment thread touched on a lot of related issues and is worth a read. In particular, I’d like to note again that domestic pig skulls are not notably paedomorphic with respect to wild boars, other than having short snouts–they’re on a different morphogenetic trajectory (Evin et al. 2016).

For a nice comparison of domestic pig and wild boar skulls, see Marcus Bühler’s post at Bestiarium, here.

UPDATE just a few days later: for a skeptical look at the very existence of domestication syndrome, see the new Lord et al. (2019) paper, “The history of farm foxes undermines the animal domestication syndrome”, freely available here.

References

Long-term readers will remember that way back in the pre-history of this blog, I wrote about my experience de-fleshing a pig head, which because the very first part in our ongoing series Things to Make and Do. In a subsequent post with a sheep-skull multiview, I included the multiview of that pig skull, too. Here it is:

Mike’s first pig skull, cranium only. Top row: dorsal view, anterior to right; middle row, from left to right: posterior, right lateral and anterior views; bottom row: ventral view, anterior to right.

As I noted in that sheep-skull post, I no longer own that skull: I donated it to be the first prize for the quiz in the very first TetZooCon, and it was won by Kelvin Britton.

But around the same time, our church hosted a barbecue even in which an entire pig was slow-roasted, and at the end of it I took the head home and prepped the skull out of it. The bone was much more fragile for having been roasted instead of simmered, and was in some danger of crumbling apart, but I stablised it with diluted PVA and it holds together OK.

Here it is:

Mike’s second pig skull, cranium and mandible in articulation. Top row: dorsal view, anterior to right; middle row, from left to right: posterior, left lateral (reversed) and anterior views; bottom row: ventral view, anterior to right.

Even allowing that the new skull was photographed with the mandible in place, the difference between the two is shocking. In particular, check out the dorsal views: the zygomatic arches of the first pig protrude way further laterally, and are much more robust than those of the second pig, and the whole shape of the skull roof is different.

I’m not sure what to make of this. I assume what we’re seeing here is variation of different breeds within the single domesticated species Sus domesticus, analogous to the way bulldog and greyhound skulls differer dramatically despite both being breeds of Canis familiaris. There are a lot of pig breeds out there, so perhaps it’s not too surprising. On the other hand, while the different dogs were bred for different purposes, I’d have thought all the pig were bred for the same purpose: to put on weight and provide meat. So I don’t know why such different skulls would have been selected for.

Well, it’s time. Ten years and almost 5 months after Mike kicked off our “Things to Make and Do” section with his post on cleaning a pig skull, I am finally getting around to prepping a pig skull of my own. There will be a complete play-by-play coming, but for now I want to focus on what is usually the least-pleasant step in prepping a skull: extracting the brain. Aside from the relatively small and often tortuous passages for the cranial nerves, the braincase is a cul-de-sac, with a big glob of tissue (the brain and associated meninges and vessels) only accessible through a relatively small hole at the back of the head (the foramen magnum). Virtually every tutorial and how-to on prepping skulls has some section where the author advises you to basically swirl something around in there, get stuff out the best you can, and prepare to deal with a lot of nastiness along the way. So I had my antennae out for anything that might help, and in the local dollar store I ran across the beauty shown above.

I figured drain rooter = brain rooter, and I was only risking a buck, so I picked one up. It worked a trick: by putting the pig’s snout down the drain, running hot water into the foramen magnum to continually flush out the loose bits, and vigorously exploring the cranial cavity with the brain rooter, I was able to get the whole brain out in about 10 minutes. To be clear, all the tissue came out the foramen magnum; there would be no way to get it to come out the nose without breaking the ethmoid bone and destroying the nasal turbinates. I only put the head snout-down for ease of access. I had a great deal of control, and I could tell pretty well which areas were getting emptied out and which still needed work. All I missed was a small glob of meninges and dural venous sinuses, which came out easily after the first simmer.

Some specific advantages of the drain rooter as a brain extractor:

  • backward-pointing teeth to hook out the tissue
  • flexible plastic so you can go pretty hard with it without damaging the bone
  • super long so you’re not going to find a job too big for it, OR you can cut it to length
  • still works for unclogging drains
  • dishwasher safe
  • dirt cheap

Go have fun.

UPDATE: Turns out pigs have an insane amount of cartilage and mucosa in their nasal cavities, and the brain rooter is pretty good at getting that stuff out, too.

The stupidest head

August 21, 2019

Left: Homo sapiens, head, neck and upper trunk in right lateral view (unprepared specimen). Right: Camarasaurus sp., skull in left lateral view. Photograph at the Natural History Museum of Utah, Salt Lake City, Utah. 2016.

Last September I spent a day in the LACM Herpetology collections with Jessie Atterholt, looking at weird features in crocs, lizards, snakes, and salamanders. I’ll have more to say about the specific things we were looking for in a month or so, after Jessie’s given her talk at SVPCA. This was just an incidental hit. We were looking at cryptobranchid (literally “hidden gill”) salamanders, because they’re big enough that you don’t need a microscope to see all their weird features. Cryptobranchids include the North American hellbender, Cryptobranchus alleganiensis, and the giant salamanders of China and Japan, Andrias davidianus and Andrias japonicus, respectively, plus a raft of fossil taxa.

This is the mandible of LACM 162475, a specimen of Andrias davidianus, in right lateral view. I’d never spent quality time with the skeleton of a giant salamander, and I was impressed with how evil their teeth are. Just in terms of general outline, these little murder-sticks wouldn’t look out of place in the jaw of a dromaeosaur. Click to enfangenate.

Jessie did an Instagram post on the upper jaw of Cryptobranchus a few months ago, and as long as you’re over there, have a look at the half a pig head that she just plastinated for our colleagues in WesternU’s College of Veterinary Medicine. It’s not the same pig as the one we hemisected last December, but I think it got cut at the same time.