Vanessa Graff and I spent yesterday working in the herpetology and ornithology collections at the Natural History Museum of Los Angeles County (LACM). The herpetology collections manager, Neftali Comacho, pointed us to this skull of Alligator mississippiensis. It’s not world’s biggest gator–about which more in a second–but it’s the biggest I’ve seen in person. Normally it lives in a big rubbermaid tub in the collections area, but this Sunday it will be out on display for Reptile and Amphibian Appreciation Day (RAAD) at the LACM. RAAD will include guest talks, tours of the collections, and live animal demonstrations. If you’re in SoCal and you’re into herps–or have kids, grandkids, nephews or nieces that are into herps–it will be well worth checking out. While you’re there, don’t neglect the newly renovated Age of Dinosaurs and Age of Mammals halls, which are frankly phenomenal: spacious, well-lit, loads of actual material on display, skeletons you can walk all the way around, informative but unobtrusive signage, tasteful integration with existing architecture…I could go on. Better if you just go and see for yourself.

About that gator. First the bad news.  It came to the LACM from another collection, and has no data–no locality, no date collected, nothing. The skull is also missing all of its teeth, the left retroarticular process, the back end of the braincase and the occipital condyle. I think the latter losses were probably caused by a foramen of Winchester.*

Now, the awesome news. The length from the snout tip to the end of the articulars was 680mm and from the snout to the end of the quadrates was 590mm. Irritatingly I did not get a dorsal head length, which is the gold standard for comparative croc skull measurements, because I only reread Darren’s giant croc skull post after I got home last night. Going from the photos, I think the dorsal head length was right around 50 cm (beware, the yardstick in the photos is marked off in inches).

Darren’s post led me to this one, which has some very useful measurements (yay!) of giant croc skulls. The table at the end of that post lists alligator skulls with dorsal head lengths of 58, 60, and 64 cm, so the big LACM gator is nowhere near being the world’s largest. In fact, the 64 cm skull would be a quarter again as large, which is a truly horrifying thought. Still, it’s a big damn skull from a big damn gator.

You might get the impression that here in the Wedel lab we are shamelessly obsessed with giant saurians. And that is in fact true. But we also look at tiny ones, too. Here I’m playing with the skull of a little Tomistoma, the false gharial. Tomistoma is notable because another individual of the genus produced the longest skull of any known extant crocodilian–a whopping 84 cm dorsal head length (photos of this monster are in both of the giant croc skull posts linked above).

The moral of the story? If the sign says don’t go swimming, don’t go swimming. Go to RAAD instead, and see the giant alligator skull, and a ton of other cool stuff besides. And if you’re into gator skulls or just like geeking out on awesome anatomy, check out the 3D Alligator Skull site, a joint project of the Holliday lab and Witmer lab. Have fun!

* bullet hole

The work continues

August 27, 2011

Not always solemnly.

Wedel’s Theorem:

freezer full of interesting dead animals + great anatomy student who actually wants to get up on Saturday morning and dissect = happiness

The rhea has been the gift that keeps on giving. Saturday was my fourth session with some part of this bird, going back to 2006 (previous posts are here, here, and here). The first two sessions were just about reducing the bird to its component parts, and the last session was all about midline structures.

The goal for the neck is to dissect down to the vertebrae and document everything along the way–muscles, tendons, fascia, blood vessels, and especially diverticula. In the past I have been pessimistic about the chances of seeing diverticula without having them injected with latex or resin or something. But this bird is changing my mind, as we saw in a previous post and as you can see below.

The goal for Vanessa is to grok all of this anatomy, and hopefully make some publishable observations along the way. She has a chance to do something that I think is rather rare for a sauropod paleobiologist, which is to get a firm, dissection-based grounding in bird and croc anatomy before she first sets foot in a museum collection to play with sauropod bones.

That sounds awesome, and probably will be awesome, but before there can be any awesomeness, the fascia has to be picked off the neck. And by ‘picked’ I mean ‘actually cut away, millimeter by arduous millimeter’. It wasn’t that bad everywhere–the fascia over the long dorsal muscles came off very easily. But the lateral neck muscles were actually originating, in part, from the inner surface of the fascia. That’s not unheard of, it happens in the human forearm and leg all the time, but I’ve never seen it as consistently as in this rhea. So picking fascia took a loooong time–that’s what Vanessa is doing in the photo at top.

Once the fascia was off, Vanessa started parting out the long tendons of the hypaxial muscles in the left half of the neck. Meanwhile, I started stripping fascia from the right half. I had forgotten that the right half of the neck still had the trachea and esophagus adhered to the side. That probably sounds weird, given that our trachea and esophagus–and those of most mammals–run right down the middle of our necks and aren’t free to move around much. In birds, they’re more free-floating and can drift around between the skin and the vertebral muscles, sometimes even ending up dorsal to the  vertebral column–there’s a great x-ray of a duck in a  2001 paper that shows this, which I’ll have to blog sometime.

Anyway, when I cut the fascia to pull back the trachea and esophagus, I found that they were separated from the underlying tissues by a dense network of pneumatic diverticula winding through the fascia.

I had heard, anecdotally, of networks of diverticula described as looking like bubble wrap. I can now confirm that is true, for at least some networks. What was especially cool about these is that they were occupying space that would be filled with adipose or other loose connective tissue in a mammal, which illustrates the point that pneumatic epithelium seems to replace many kinds of connective tissue, not just bone–something Pat O’Connor has talked about, and which I also briefly discussed in this post.

I should mention that there was no connection between these diverticula and the trachea, as there is between the subcutaneous throat sac and the trachea in the emu (story and pictures here).

While I was geeking out on diverticula, Vanessa was methodically separating the long hypaxial muscles, which looked pretty cool all fanned out.

And that’s all we had time for on Saturday. But we’re cutting again soon, so more pictures should be along shortly.

On a lighter note…

August 21, 2011

Something about this photo from the last post has been bugging me all week. It’s the expression on my face. The set jaw, the thrust forward chin, the cocked eyebrow…I knew I had seen these things before. It took me a while, but I was finally able to place it. My doppelganger:

If this is an omen, I have no idea what it means.

Science will resume shortly.

It’s an anniversary of sorts. Not today, nor any particular day this year, but this year, 2011, marks my 15th year doing research. The last time I blogged about this was the 10th anniversary, back in 2006. Back then I was in my fifth year as a PhD student in Kevin Padian’s lab at Berkeley. I knew I’d have to finish and get a job, but I had no idea how either of those things was going to happen. And although I talk a big game about seeking out new experiences, I was flatly terrified. But things have worked out. I have a tenure-track job doing what I love, research is still rolling along, and life continues to change in unexpected ways. Time’s arrow flies on.

If that paragraph seemed insufferably self-absorbed, don’t worry. This isn’t my story anymore.

I’m taking on my first graduate student this semester: Vanessa Graff, who is pursuing a master’s degree through the Graduate College of Biomedical Sciences here at WesternU. Vanessa’s going to be a doctor someday, but for the immediate future she’s signed on as a sauropod paleobiologist in training.

My feelings about this are complex. I am acutely aware of exactly how nowhere I’d be without the generosity and guidance of Rich Cifelli, Kevin Padian, Bill Clemens, and the host of people who showed up in my life at the right time and said the right words to steer me to where I am now. Fifteen years ago I had a conversation with Trish Schwagmeyer that literally changed the course of my life. It started with her reviewing my less-than-mediocre grades, looking me in the eye, and saying, “You’re blowing it”, and ended with her recommending that I find a faculty sponsor for an independent study (ultimately, this). I have been walking around with that debt for my entire adult life (if I’d been an adult in 1996, we wouldn’t have needed to have that talk). And although I have thanked Trish and told her how pivotal that conversation turned out to be, I can’t ever pay that back. Or any of the rest, that I owe to more people than I can readily count.

But now, unexpectedly, I have a chance to start–just start–paying it all forward. I don’t have any delusions that I will do so perfectly. Rich, Kevin, and Bill were all seasoned pros when they took me on. Whereas I…well, let’s acknowledge that I’m no Rich Cifelli and leave it at that, shall we? So as a first-time advisor I oscillate between exhilaration and sheer terror–come to think of it, pretty much the same as I did as a PhD candidate at Berkeley, and as an undergrad at OU. Plus ça change

I closed the Acknowledgments of my dissertation with, “Everything they ever taught me has paid off. I have tried to make my career an act of thanks.” At the time I was writing about my parents, but now I have the perspective to see that I was actually writing about my advisors as well. Four years out of the nest, and once again I find myself following their example as I attempt something I’ve never done before. Like everything I do as a professional, my actions will be imperfect imitations of theirs, somewhere on the spectrum between homage and pastiche.

But like I said, it’s not my story anymore. It’s Vanessa’s. And in the brief time that we’ve been working together she has shown more grit and maturity than I had at her age, and just as much enthusiasm. I am confident that her surpluses in those areas will carry her through my inevitable fumbles. She is rolling, and there is the familiar sense of a snowball at the top of a mountain, at the moment where motion goes from potential to perceptible to inevitable.

Where will that motion take her? Beats me. We’ll find out as we go–just like I did with Rich and Kevin and Bill. That will be Vanessa’s story to tell, in conference presentations and papers and whatever other venues she chooses. I’ll help her all I can, and hope for the good sense to know when to nudge and when to get out of the way.

Rich, Kevin, Bill–you left me some damn big shoes to fill. I will not succeed, not completely. But I will strive to make my advising an act of thanks.