Otters are a “near-threatened” species in the UK, so it’s a tragedy when one is killed by a car. That said, when a roadkill otter is spotted by a friend and delivered to me five days after Christmas, that goes some way to redeeming the tragedy.

So far as I can determine, while otters are protected by law in the UK, there’s nothing saying that a roadkill otter can’t be kept for scientific purposes. So here is Eleanor the dead otter:

It shouldn’t come as a surprise to me, but it does, to find that an otter is a pretty substantial animal. Mine measured at 111 cm from snout to tail, and 69 cm from snout to the base of the tail. Here’s where I considered the base of the tail to be:

Maximum girth is difficult to measure. I ended up taking three measurements: when the tape is left relaxed around the torso, it yielded 50 cm; when I tightened it as one does with a belt, it came down to 44 cm; and I judged that 48 cm was the best true value.

The animal masses about 7.6 kg — including the neglilgible weight of two Lidl carrier-bags that I wedged it into. That compares with 5.2 kg and 100 cm total length for a fox that I buried ten years ago, and a very impressive 12 kg and 75 cm for a badger of the same vintage. (These are not the same fox and badger that I decapitated a while ago, but from memory they were about the same size.)

Like the badger — though not to the same extent — the otter is a serious piece of animal. It has short, heavily muscled forearms that I would not want to be on the wrong end of:

Its head is not obviously damaged, but with its eyes closed and its mouth clamped shut in rigor mortis, there’s not much to see at this stage:

That will obviously change when I get its skull out — but that is a project for the spring. It’s too cold and nasty outside for this kind of work. For now, Eleanor will rest in peace in our woodshed.

An otter is a rare find, and I have no expectation of ever acquiring another one — unlike foxes and badgers, which crop up maybe once a year or so on average. So I hope I can make the time to treat this with the reverence it deserves, and extract the whole skeleton (as I did with my monitor lizard) rather than just the charismatic skull.

Answers to frequently asked questions

No, I did not kill this otter.

No, I do not endorse the killing of otters.

No, I did not find it myself. It was found by a friend whose identity I will not disclose just in case I am mistaken about the legality of collecting roadkilled otters in the UK.

Yes, I respect the dignity of wild animals.

No, I don’t consider it more dignified for a carcass to rot by the side of a road than to be used for scientific purposes.

Yes, I am completely cool with my own body being used for science after I die.

 

In lieu of any new science today, have some memes, and a wonderful day!

A timeless classic.

In case you’re wondering, that’s “rolling on the beach laughing my telson off”. Horseshoe crabs have been around for 445 million years, about twice as long as mammals, turtles, and dinosaurs.

Made this last Friday afternoon, in lieu of other stuff I should have been doing. I’m gloating now because the campus is closed and I’m untouchable! Mwa-ha-ha-HAAA!!

Natural selection is a pathway to many abilities that some consider to be…fully rad.

Something big is coming

December 24, 2019

Since 2015 I’ve been working in the Morrison Formation of Utah with Brian Engh, John Foster, ReBecca Hunt-Foster, and more recently Jessie Atterholt and Thuat Tran. Other than a couple of very short, detail-free mentions (like this one), I’ve been pretty quiet about most of our work out there—we all have—but it’s time to start showing everyone what we’ve been up to. Check out this trailer for a pair of documentaries that Brian has been working on. Coming soon!

Arm lizard

December 16, 2019

Reconstructed right forelimb of Brachiosaurus at Dinosaur Journey in Fruita, Colorado, with me for scale, photo by Yara Haridy. The humerus is a cast of the element from the holotype skeleton, FMNH P25107, the coracoid looks like a sculpt to match the coracoid from the holotype (which is a left), and the other elements are either cast or sculpted from Giraffatitan. But it’s all approximately correct. The actual humerus is 204cm long, but the distal end is eroded and it was probably 10-12cm longer in life. I don’t know how big this cast is, but I know that casts are inherently untrustworthy so I suspect it’s a few cm shorter than it oughta be. For reference, I’m 188cm, but I’m standing a bit forward of the mount so I’m an imperfect scale bar (like all scale bars!). For another view of the same mount from five years ago, see this post.

So I guess the moral is that even thought this reconstructed forelimb looks impressive, the humerus was several inches longer, even before we account for any shrinkage in the molding and casting process, and the gaps between the bones for joint cartilage should probably be much wider, so the actual shoulder height of this individual might have been something like a foot taller than this mount. A mount, by the way, that is about as good as it could practically be, and which I love — I’m including all the caveats and such partly because I’m an arch-pedant, and partly because it’s genuinely useful to know all the ways in which a museum mount might be subtly warping the truth, especially if you’re interested in the biggest of the big.

All of which is a long walk to the conclusion that brachiosaurs are pretty awesome. More on that real soon now. Stay tuned.

When I visited Dinosaur National Monument in October with Brian Engh and Yara Haridy, we spent a decent amount of time checking out DNM 28, a skull and associated bits of Camarasaurus. In particular, I got some shots of the axis (the second cervical vertebra behind the head), and it got me thinking about pneumaticity in this unusual element. Why I failed to get a full set of orthogonal shots is quite beyond my capacity, but we can roll with what I have. Before we go on, you might want to revisit Tutorial 36 to brush up on the general parts of the atlas-axis complex.


Here’s the axis in left lateral view (so, anterior to the left).

And a labeled version of the same. A few things to note:

  • One oddity of sauropod axes (and of axes of most critters) is that not only are the articular facets of the prezygapophyses not set forward of the neural arch, they’re set backward, well behind the forward point of the arch.
  • The dens epistrophei or odontoid process is sticking out immediately below the neural canal. This is the tongue of bone that articulated with the atlas (first cervical vertebra) in life.
  • Check out the prominent epipophysis above the postzygapophysis, which anchored the long dorsal neck muscles. (For more on epipophyses, see these posts, and especially this one.)
  • The diapophysis and parapophysis articulated with a cervical rib, which is not shown here. In fact, I don’t remember seeing it in the drawer that this vert came from. The atlantal and axial cervical ribs are small, apparently fused late in life if they fused at all, and are easily lost through taphonomic processes.
  • At least three pneumatic features are visible in this lateral view: the lateral fossa on the centrum, which is referred to as the “pleurocoel” in a lot of older literature; a ventral fossa that lies between the parapophysis and the midline ventral keel; and a fossa on the neural arch, behind the postzygodiapophyseal lamina. In the nomenclature of Wilson et al. (2011), this is the postzygocentrodiapophyseal fossa.

“Postzygocentrodiapophyseal fossa” is a mouthful, but I think it’s the only way to go. To be unambiguous, anatomical terminology needs to references specific landmarks, and the schemes proposed by Wilson (1999) for vertebral laminae and Wilson et al. (2011) for vertebral fossae are the bee’s knees in my book.

Nomenclatural issues aside, how do we know that these fossae were all pneumatic? Well, they’re invasive, there’s no other soft-tissue system that makes invasive fossae like that in archosaur vertebrae (although crocs sometimes have shallow fossae that are filled with cartilage or fat), and the same fossae sometimes have unambiguous pneumatic foramina in other vertebrae or in other sauropods.

Most of the features labeled above are also visible on the right side of the vertebra, although the ventral fossa is a little less well-defined in this view, and I can’t make out the prezyg facet. Admittedly, some of the uncertainty here is because of my dumb shadow falling across the vertebra. Specimen photography fail!

The paired ventral fossae are more prominent in this ventral view, on either side of the midline ventral keel (anterior is to the top).

And here’s a labeled version of the same ventral view.

Finally, here’s the posterior view. It’s apparent now that the neural spine is a proportionally huge slab of bone, like a broad, tilted shield between the postzygapophyses (which are also quite large for the size of this vertebra). The back side of the neural spine is deeply excavated by a complex fossa with several subfossae (kudos again to Jeff Wilson [1999] for that eminently useful term).

Here’s the same shot with some features of interest labeled. If I’ve read Wilson et al. (2011) correctly, the whole space on the back side of the neural spine and above the postzygs could be considered the spinopostzygapophyseal fossa, but here I’ve left the interspinous ligament scar (ILS) unshaded, on the expectation that the pneumatic diverticula that created that fossa were separated on the midline by the interspinous ligament. I might have drawn the ILS too conservatively, conceivably the whole space between the large deeply-shadowed subfossae was occupied by the interspinous ligament.

I’m particularly interested in those three paired subfossae, which for convenience I’m simply calling A, B, and C. Subfossa A may just be the leftover space between the spinopostzgyapophyseal laminae laterally and the interspinous ligament medially. I think subfossa B is invading the ramus of bone that goes to the epipophysis and postzygapophysis, but I didn’t think to check and see how far it goes (that might require CT anyway).

Subfossa C is the most intriguing. Together, those paired fossae form a couple of shallow pits, just on either side of the midline, and aimed straight forward. They can’t be centropostzygapophyseal fossae, which used to be called peduncular fossae, because they’re not in the peduncles on either side of the neural canal, they’re up above the lamina that connects the two postzygapophyses. Could they be ligament attachments? Maybe, but I’m skeptical for at least four reasons:

  1. Although interspinous ligament attachments often manifest as pits in the cervical vertebrae of birds, in sauropods they usually form rugosities or even spikes of bone that stick out, not inward. Furthermore, these pits are smooth, not rough like the interspinous ligament scars of birds.
  2. The interspinous ligament in tetrapods is typically a single, midline structure, and these pits are paired.
  3. Similar pits in front of the neural spine are present in some sauropod caudals, and they appear to be pneumatic (see Wedel 2009: p. 11 and figure 9).
  4. Pits at the base of the neural spine seem to be fairly uncommon in sauropod vertebrae. If they were attachment scars from the universally-present interspinous ligaments, we should expect them to be more prominent and more widespread.

But if these paired pits are not ligament scars, what are they? Why are they present, and why are they so distinct? Sometimes (often?) subfossae and accessory laminae look like the outcome of pneumatic diverticulum and bone reacting to each other (I almost wrote ‘playing together’), in what looks like a haphazard process of adaptation to local loading. But the symmetry of these pits argues against them being incidental or random. They don’t seem to be going anywhere, so maaaybe they are the first hoofbeats of the embossed laminae and “unfossae” that we see in the vertebrae of more derived sauropods (for which see this post), but again, their symmetry in size and placement isn’t really consistent with the “developmental program gone wild” appearance of “unfossae”. I really don’t know what to make of them, but if you have ideas, arguments, or observations to bring to bear, the comment field is open.

In summary, sauropod axes are more interesting than I thought, even in a derpasaurus like Cam. I’ll have to pay more attention to them going forward.

References

 

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.