Things to Make and Do, part 6c: fragments of ostrich skull
June 25, 2010
After the third simmering, Veronica the Ostrich Head started to come apart beautifully — more so than she should have done in one or two places, as it became apparent that her skull, as well as being incompletely fused due to presumed subadult age at time of death, was slightly damaged. Still, I’ve been able to tease the bones apart nicely, remove pretty much all the remaining soft tissue, and figure out where most bits go, well enough that I think I’ll be able to put her back together once everything’s been cleaned.
Here’s my girl as she emerged from the pot (cranium only — the mandible was separate by this point). What may not be apparent here is just how fragile she was by this stage: I had to hold her snout as well as the main part of the skull to prevent it from falling off. You can see that it’s skewed a little sideways, rotating clockwise with respect to the rest of the skull so that the posterodorsally oriented midline “tongue” of bone is off to the left (our right), and lies alongside the central bulging bone rather than overlying it as in earlier stages.
The squamosals are still in place at the sides of the back of the skull, but they came away very easily, and cleaned up nicely.
I carefully removed the snout, and was astounded to see how very thin the bones that connect it to the rest of the skull laterally are:
The midline bone here apparently is the fused ascending processes of the premaxillae, despite my having said last time that it probably wasn’t — thanks to Nick Gardner for putting me straight. but what are the posterolaterally directed spines? Can they also be processes of the premaxillae? Or are they the maxillae? I think the former: read on.
It’s hard to tell in part, of course, because of the horny beak which obscures whatever sutures might be up there at the front of the skull. I don’t want to remove that, partly for fear of causing damage to the bones but mostly just because it’s nice to keep. What I’d not appreciated until I started this exercise is that there’s no hard demarcation between beak and soft-tissue, but they grade into each other so that the posteriormost preserved parts of the beak are not horny at all, but rubbery — even stretchy. It’s hard to know how much of this to remove. If there’s a Standard Operating Procedure, I don’t know it — anyone? Maybe I’ll leave the snout in a bug-box and let the dermestids decide. (Let the Dermestids Decide would be a good title for a debut novel, and its Oscar-winning movie adaptation.)
(Of course this continuous gradation between tissue types is familiar to all of us who’ve ever tried to remove the cartilage from a skeleton: in some cases, like the cartilage caps on long bones, there’s clear bone and clear cartilage, but in other cases it’s not so well-defined. Think, for example, of the partially ossified but partially cartilaginous breastbone of a chicken — take a look the next time you have a Sunday roast. This is a real problem in cleaning skeletons.)
Once I’d removed the snout, here’s what remained:
On the midline, half way along the remaining skull (i.e. anteromedial of the orbits) is a very fragile self-contained bony capsule which seems to be full of some kind of soft tissue — maybe fat. It’s not easy to make out its boundaries in this photo, so here is another that I took of the skull after lifting the capsule out — you can see it in the background. Does anyone know what the capsule is? My feeble bird-skull literature isn’t telling me anything about this.
With this capsule gone, it was with me the work of a moment to lift out the two big, spongy, soft-tissue masses from in front of the orbits, which you’ll remember I decided not to attempt last time. A very good decision that proved. Having removed them, I found a neat cartilaginous midline structure which I’d like to preserve for the final reconstruction of the skull, but which is already changing shape dramatically as it dries up so I fear I’m going to have to let it go. Anyway, the bony structure of the remainder of the skull is now much more apparent:
I am guessing that the anteriormost lateral bones are the maxillae, which are a super-weird shape. As you can see, the left bone is broken: its anterior portion is missing. Happily, I have this bit, and it’s a perfect fit for the posterior part, so a bit of superglue should fix this problem — but it does emphasise just how insanely delicate many of the skull bones are.
I think the “wing” bones projecting laterally from near the back of the skull must be quadrates: if so, then the bones that project anteriorly from them are quadratojugals, which shade into straight, elongate jugals (you can see the junction in the near side of the photo above) and then connect with the maxillae.
The midline bone, which is surprisingly robust, seems to be made up of fused vomers or somethingat the front, and the parasphenoid rostrum to the rear [thanks to Nick Gardner for this and other corrections]. They’re hard to see in this photo, but there’s also a pair of oddly shaped more-or-less horizontal plates ventrolateral to this midline bone (I think they must be the palatinespterygoids) and two longer, narrower bones anterior to these (which might be the vomers, in which case the fused midline bones are something else? are the palatines).
Once I’d removed all these, I was left with a solid braincase fused together with that midline bone that might be vomersmade up of the parasphenoid rostrum and vomers. And that, with surprising suddenness, was that.
So here is the complete set of skull bones, laid out in something resembling their order in life: top of the skull at the top of the picture, facing left, with vertebrae to their right; bottom half of the skull (mandible first, then palate) at the bottom of the picture, also facing left. (Sorry that the contrast is not great: the sun was almost down by the time I took this photo):
When I looked at this, I was reminded of a passage in one of Dave Barry’s old columns, ‘Mister Mediocre’ Restaurants, in which he proposed some surefire business ideas, including a place where you could have your non-functional gadgets permanently destroyed:
The idea there was that consumers would bring their broken electronic devices, such as television sets and VCR’s, to the destruction centers, where trained personnel would whack them (the devices) with sledgehammers. With their devices thus permanently destroyed, consumers would then be free to go out and buy new devices, rather than have to fritter away years of their lives trying to have the old ones repaired at so-called factory service centers, which in fact consist of two men named Lester poking at the insides of broken electronic devices with cheap cigars and going, Lookit all them WIRES in there!
Similarly, I found myself thinking: lookit all them BONES in there!
Happily, help was on the way: Nick Gardner sent me a copy of Maxwell 2009, which has a few useful figures, and from these I was able to take pretty good guesses on the identities of more of the bones. (That’s why I’ve included more guesswork above than in previous articles in this series.) So I leave you with an annotated version of the photo above, with my best guess at identifying the bones. PLEASE MAKE CORRECTIONS IN THE COMMENTS — I will make up a revised version of this annotated photo once they’re all in. For for now, here it is Here is the initial version, which Nick critiqued in the comments:
And here is the corrected version, so far at least:
Now let’s get those corrections going!
- Maxwell, Erin E. 2009. Comparative ossiﬁcation and development of the skull in palaeognathous birds (Aves: Palaeognathae). Zoological Journal of the Linnean Society 156:184-200.