October 17, 2014
This arrived on my Facebook wall, courtesy of Raul Diaz. For a split second I really did think the one second from the right was an older-model Carnegie Brachiosaurus toy.
I assume that, like me, you have people in your life that you don’t correspond with very often, and when you remember that they exist, it just makes you happy. Like, yeah, there’s a slightly higher chance that our species is going to make it, just because that person is out there in the world, doing what they do. Raul is in that category for me. He’s a herpetologist, but that term doesn’t really do him justice; Raul is into herps like Genghis Khan was into real estate acquisition.
Now he’s an Assistant Professor at La Sierra University and also teaches at the Loma Linda University School of Medicine (Raul, that is, not Genghis Khan). But I’ve known him since he was an undergrad. He was a student in one of my discussion sections for the evolution course at Berkeley. I had a tradition in all the classes I taught as a grad student: on the last class meeting I’d have people bring food and we’d have a little potluck. Raul showed up with a six-pack of Pabst Blue Ribbon. No-one else was partaking, so Raul and I spent 50 minutes drinking PBR and talking about descent with modification. Good times.
Oh, and the “tiny brontosauruses” are actually coatis, genus Nasua, raccoon relatives that range from the southwestern US to northern South America. Surprisingly, I don’t think that Darren has ever covered coatis in detail at TetZoo; maybe this will spur him into action.
October 15, 2014
October 5, 2014
Remember I picked up those three sheep skulls (and some other bones, including a complete neck) from a shallow pit in a field near where we live? Here is first first of the skulls, cleaned up and photographed in orthogonal views.
It’s interesting to compare it to the pig skull from way back:
Sheep and pigs are both perfectly well-behaved artiodactyls, but their skulls are dramatically different. The pig is extraordinarily more robust, and has absolutely massive jaw-muscle fossae.
The sheep would have been difficult to prepare by the usual simmer-and-slice method — too easy to damage, especially inside the nasal cavity, where the respiratory turbinates are very fragile. The pig is a much easier proposition. I was able to clean out its nasal cavity just by running water through it at fairly high pressure, without doing any damage.
For anyone who wants to get into skull preparation, I definitely recommend starting with a pig.
October 1, 2014
Just over a year ago, in his write-up of the Edinburgh SVPCA, Matt included a photo of me standing in front of a Giant Irish Elk (Megaloceros), positioned so that the antlers seem to be growing out of my head. Matt finished his post with a background-free version of that photo, and commented:
… so he can be dropped right into posters, slide shows, and other works of science and art. I really, really hope that he turns up in conference talks and other presentations in the months and years to come. If so, send us a photo documenting his miraculous apparition and we’ll show it to the world.
It has come to pass.
Last week, Vladimir Socha gave a presentation about “famous paleontologists” during the “Night of the Scientists” event:
(I think that’s Bakker on the left of the slide.)
Here’s one of his slides:
Yep. That’s the Queen of England at the top, and me, her subject, beneath. With antlers.
Here’s a cleaner version of the slide that Vladimir sent me:
Apparently the text translates as:
Paleontologists should have a sense of humour, too. On the internet, this is largely shown for example by british computer programmer and sauropod expert Michael P. Taylor (*1968).
So there you go. I made it into “famous paleontologists”, ahead of a vast number of far worthier candidates, because of my antlers.
I think there’s a lesson there for all of us.
But I’m darned if I know what it is.
September 30, 2014
Just a quick photo-post today. A couple of months ago, walking around the fields near our house, I found a broad shallow pit with a lot of a sheep skeletal elements in it. I took my youngest son out on an expedition, and we rescued the good material. I’ve cleaned up the first two (of three) skulls. Here is the smaller of the two — which is also more complete, and the big one has lost its nasals.
Click through for glorious high-resolution (4000 x 3000, and not a pixel wasted).
I took a nice set of orthogonal-view photos of this skull. When I have time, I will clean them up and composite them as I did with my pig-skull, which I’m sure you all remember:
(Well … I call it my pig skull, but it’s not mine any longer. I donated it as the prize for winning the TetZooCon quiz, and it is now the proud possession of Kelvin Britton. But I have another one, so that’s all right.)
September 23, 2014
Here’s a thing I put together to help my students understand the many branches of the internal iliac artery in humans. In the image above, we’re looking in superomedial view into the right half of the sacrum and pelvis. Bones are white, ligaments blue, the piriformis muscle sort of meat-colored, and arteries red (for a tour of the pelvis identifying all of this stuff, see my pelvic foramina slideshow). At the top is a big inverted Y-shape: the common iliac arteries branching from the abdominal aorta, which continues on, much reduced, as the median sacral artery. The right common iliac artery is shown bifurcating into the external iliac artery, which continues on out of the pelvis to become the femoral artery, and the internal iliac artery, source of much fear and doubt.
The first thing to understand is that any particular branching pattern of the internal iliac arteries, whether in an anatomical altas, a lecture, revealed in a dream, or even in your own body, will probably have no bearing whatsoever on the branching pattern in the next person you encounter, alive or dead. Furthermore, the variation between right and left in a single person can be as great as that among different people. The branches to pelvic viscera are particularly fiendish; they sometimes travel far into the pelvis as a common trunk and then “starburst” near their target organs, making identification almost impossible. Do not waste your time trying to memorize any particular branching sequence. Instead, concentrate on matching the arteries to their targets; you will discover the identities of the branches by seeing where they are going, not the order in which they branch.
There are typically 10 named branches of the internal iliac artery. Authorities quibble on the details, as we’ll see in a moment, but if you know these 10, you’ll be fine for almost any conceivable purpose. A simple scheme of my own devising for remembering them is 2-4-4:
TWO to the back body wall:
- iliolumbar A—may arise from external or common iliac AA; sometimes double
- lateral sacral A—note branches to anterior sacral foramina and anastomoses with median sacral A
FOUR leaving the pelvis entirely:
- obturator A—often arises from the external iliac A instead, exits pelvis through obturator canal
- superior gluteal A—exits pelvis through suprapiriform foramen
- inferior gluteal A—exits pelvis through infrapiriform foramen, with internal pudendal A
- internal pudendal A—exits pelvis through infrapiriform foramen, with inferior gluteal A
FOUR to pelvic viscera:
- superior vesical A—usually the dominant artery of the anterior trunk, this is the patent part of the obliterated umbilical artery, which survives as the medial umbilical ligament
- inferior vesical A (males) / vaginal A (females)—may branch off uterine A (females) or superior vesical A (both)
- uterine A (females)—major artery to uterus, approaches laterally within the broad ligament
A to ductus deferens (males)—extremely small and difficult to trace
- middle rectal A—usually the most inferior branch of the entire internal iliac tree (at least inside the pelvis)
My way to explain those last four is to extend my index finger and say, “Everybody has to pee, so up front we have superior vesical.” Then extend my pinky and say, “And everyone has to poop, so in back we have middle rectal.” Then extend digits three and four and explain that the identity of the middle two arteries varies between the sexes (but that the inferior vesical artery of males and the vaginal artery of females are basically the same vessel).
There is a LOT of variation in the descriptions of the internal iliac artery branches among different sources — almost as much variation as there is in the arteries themselves.
- The Thieme Atlas of Anatomy, 2nd Ed (Gilroy et al. 2009), Table 19.1 on p. 254, includes the inferior vesical artery for both sexes. The artery to ductus deferens is listed as a branch of the superior vesical artery, and the uterine and vaginal arteries are listed separately, bringing the total for females to 11.
- Clinically Oriented Anatomy, 7th Ed (Moore et al. 2013), Table 3.4 and pp. 350-355, lists the 10 branches I went through above. Moore et al. explicitly say that the vaginal artery is the female homolog of the inferior vesical artery (p. 351).
- Gray’s Anatomy, 40th Ed (Standring et al. 2008), pp. 1085-1089, splits the difference. The artery to ductus deferens is not listed; instead, the ductus deferens is said to be supplied by the inferior vesical A (in contrast to Thieme, which has it is supplied by the superior vesical A). Both the vaginal and inferior vesical arteries are listed, but the vaginal artery is said to frequently replace the inferior vesical artery.
The upshot is that pretty much all of these sources agree on how the blood is getting distributed, there are just some minor differences over what we call certain vessels. I have never personally seen a dissection detailed enough to allow an interior vesical artery to be recognized separately from the vaginal artery — the vagina lies so close behind the bladder that whatever you call the artery that runs lateral to them, it could easily be supplying both structures, and probably does. As far as I’m concerned, the inferior vesical artery in males and the vaginal artery in females are the same artery, in that they both supply the inferior portion of the bladder. I think it’s just a historical hiccup that we call them by different names, possibly perpetrated by smelly, lonely, vagina-obsessed men of centuries past.
A final note, added in revision: some sources refer to two trunks or divisions of the internal iliac artery: a posterior trunk that gives rise to the iliolumbar, lateral sacral, and superior gluteal arteries, and an anterior trunk that gives rise to everything else. If that’s what your professor tells you, smile and nod and keep your heretical thoughts to yourself. Personally, I regard the notion of trunks of the internal iliac artery alongside phlogiston, luminiferous aether, and snorkeling sauropods, as romantic nonsense at best. I have seen an obturator artery arise from a superior gluteal artery and a pudendal artery arise from a superior vesical artery. In a world where variants like those can and do turn up frequently, the stability and reason implied by regular trunks is illusory.
- Gilroy, A., MacPherson, B., and Ross, L. (eds.) 2009. Atlas of Anatomy, 2nd ed. Thieme, Stuttgart.
- Moore, K.L., Dalley, A.F., and Agur, A.M. 2013. Clincially Oriented Anatomy, 7th ed. Lippincott Williams & Wilkins, Philadelphia.
- Standring, S. 2008. Gray’s Anatomy, 40 ed. Churchill Livingstone, London.