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Archive for November, 2012

A vignette from research I’m engaged in with a couple of different projects follows. Below is a photo I took of two humeri (upper arm bones; humerus is singular).

One is from a Black Rhinoceros; Diceros bicornis (modern; specimen #H.6481 from the University Museum of Zoology, Cambridge), which was collected in 1873 in Bogos, Abyssinia by zoologist ?Edward? Gerrard.

The other, larger one is from a giant long-necked and (presumably) hornless rhinocerotoid; Paraceratherium [AKA Indricotherium, Baluchitherium] (extinct of course; specimen #NHMUK PV M 12251 from The Natural History Museum, London); which was collected in 1911 in the Siwalik Hills of India by palaeontologist Forster Cooper. My photo is shown with kind permission of the Natural History Museum, London.

For an idea of scale, the smaller one is 39 cm (just over a foot) long, so about the same length as your humerus, give or take a bit. It comes from an animal that probably weighed around one tonne (1000 kg; 2200 lbs) or so. Look back at the picture, and pause to reflect on the scale. This is one of the largest living land animals right here, and despite that size it is quite an athlete (watch the classic John Wayne chasing-animals-around-Africa film Hatari! if you want elegant proof, or browse Youtube videos of boisterous rhinos).

But any living rhino pales in comparison to the giant Oligocene form, whose humerus is twice the length (~80 cm; almost as long as your entire leg, probably) and quite a bit more robust. The best estimates of mass for such an animal are up to 15-20 tonnes, on a par with the largest mammoths and other elephant relatives. That’s like a ten-rhino rhino! Sure, they all pale somewhat in scale against the largest sauropods (or whales, which cheat by living in water). Yet for my money (warning: subjective value judgement ahead!) a rhinoceros is cooler than any sauropod at the same size, and sauropods are extinct so we have less left to study. (I’m being deliberately provocative for my sauropod researcher friends, but in a loving way)

The scale, and often cramped conditions, make it hard getting a good photo of a Paraceratherium skeleton or reconstruction, but here’s one I took at Tokyo’s Museum of Nature and Science.

Now, of course if you know me, you know I am thinking about how such giant land animals moved. Authors such as Gregory Paul and Per Christiansen have made arguments based on real data, both qualitative anatomy and quantitative bone dimension measurements, that even giant rhinos like Paraceratherium could trot and gallop much like living rhinos do, despite their giant size. They have inferred from the limb joint structure that these giant rhinos were more crouched, were less columnar (vertical-limbed) than living elephants are (although I’ve shown with my team that this characterization of elephants is quite misleading; they get quite un-columnar, rather crouched, as they attain faster speeds). If Paul and Christiansen were correct, it would be remarkable. I can’t definitively show either way, just yet. But I want to see how well this argument holds up with other data and methods, so I’ve been planning to test this idea for a long time. We’ll see how it goes.

Anyway, that was my brief tale of two scales. On one hand we have living “giants” in the form of the five currently remaining species of rhinoceroses, which are quite extraordinary in many ways, albeit in big trouble. On the other hand we have amazing, mysterious uber-giants like Paraceratherium, two or more times the size in linear dimensions and an order of magnitude greater in weight. Both are certainly giants by any measure of size in land animals.

But was the bigger rhino living in a rather different world, even more dominated by gravity than its smaller relative is today? (No, gravity was no different! It was only 30 or so million years ago; relatively recent!) Or did they live in relatively similar worlds of just being “bloody huge and devastatingly powerful, thank you very much”? I find that question really exciting and wondrous to ponder. What do you think?

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Hey, Americans and others happening to be gobbling down Meleagris gallopavo today– don’t forget to practice your anatomy! Such a great opportunity. Dig in to that carcass and horrify/amaze your family and friends! This pic might help you get started (info below if you want it), and is my WIJF blog wish of happiness to you all, today.

Stomach-Churning Rating: 6 out of 10; a small picture of some fresh turkey leg muscles, but not that bad really.

Click to embiggen.

Wondering what’s shown here?

On the left: an ossified (turned into bone!) tendon, probably part of the M. flexor perforans et perforatus group (a wickedly complex set of muscles that go from the knee region to the toes, and act mainly to flex the knee, extend the ankle and (plantar)flex the toes; i.e curl the toes up). What’s particularly cool is that, towards the top, you can see the divisions where the pennate (angled) fibers of the short, meaty muscle belly sat. If you are eating a turkey drumstick, you will be picking some of these out of the meat, although many turkeys seem to have fewer bony tendons due to human breeding and young age at slaughter.

In the middle, top: a crude experiment where we hung a frozen turkey’s body in a few different orientations to determine its centre of mass, important for biomechanical calculations. Mad science, but simple science.

In the middle, bottom: the right hip joint of a turkey in lateral (side) view, showing a few of the key muscles of the thigh. The ITC is M. (abbreviated Latin for Musculus) iliotrochantericus caudalis. Practice saying that (ill-ee-oh-tro-kan-tare-ick-us caw-dahl-iss) to impress your friends. It sits in a depression in the ilium (top pelvic bone), in front of the hip joint. The ITC is also important for helping birds to support their weight, as Steve Gatesy and I discussed in our 2000 Paleobiology paper. The ITC leaves a lovely crescent-shaped scar on the top of the femur (thigh bone). Show off your culinary skills by noting to your dinner party that this muscle is the best bit of the bird, AKA the “oyster”. (A little tip is here for how to find it; in a chicken but the anatomy is almost the same in a turkey)

The OM is the obturatorius medialis (obb-turr-ahh-tor-ee-us mee-dee-ahl-iss), an antagonist to the ITC, used to swing the leg. It is mostly hidden inside the pelvis so you just see its tendon (dotted line), and especially in turkeys (seriously, they have very nicely visible muscle attachments on their leg bones, for any bird!), a little knobby bit of bone that helps guide the tendon to keep it in its little groove on the femur. Unless you’re very industrious and break open the body cavity to excavate into the pelvis, you won’t be eating this muscle.

The IFE; M. iliofemoralis externus (ill-ee-oh-fem-oh-rahl-iss ex-ter-nuss); arching over the ITC and OM tendons, is a vestigial muscle, often lost in birds, and having little major function but helping a bit to draw the leg away from the body (abduction). Even though it is a puny muscle, it still has a nice little pit for its insertion on the femur. Turkeys are just cool that way. But it’s not much in the way of eating.

And now you know three of the ~40 main muscles of the avian leg, well done! 

I love these muscles not only because I did a lot of my PhD (and later) research on them, but also because they leave great scars on bird and other dinosaurian bones that allow us to reconstruct how muscles evolved. I better stop here or I’ll be writing for days… don’t wind me up further! :)

On the right: the foot of a turkey in front and back views. Lots of ossified tendons are visible if you squint. Why do birds only have ossified tendons below their knee joints, and why only some muscles in some birds, and not so commonly in most other species of land animals? This is one of those cool mysteries that remain for people doing evolutionary or biomechanics research to sort out.

Hope you enjoyed a quick anatomy tour with our pal Meleagris!

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More mysterious morphology for you

I hope that you like it too

But there is a trick

The bone here is thick

And the beast might be rude, it’s true!

(What is it and what from? Answers must be in limerick form to count. Pilot scans explained in this post.)

This post is dedicated in memory of the late, great Professor Farish Jenkins, Jr; one of the best anatomists and functional morphologists ever. Excellent retrospectives here and here and here.

Aaaaaand here is the current scoreboard, as promised last time; starting from this post onwards–

RULES: 5 pts for correct, spot-on and FIRST right answer, 4 pts for very close or second, 3 pts for partly right or third in line with right answer, 2 pts for a good try, 1 pt consolation prize for just trying, or for a good joke!

If you post as “anonymous” name then it all goes into the same tomb of the unknown anatomist.

If you change your answer, you lose ~1 pt. Answers posted via Twitter, Facebook, email or whatever do not count! No appeals. I am a frigid dictator. :-)

(more…)

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A quick report on an exciting event for my team, from this week: We got a box! A big one! With 10 frozen crocodiles.

Stomach-Churning Rating: 5 out of 10. Just 1 picture with some blood.

 

These come from a breeding centre in southern France, and died of natural causes. Here is a little, icy box of five Crocodylus moreletii, a species that has featured here before:

And five young Nile crocodiles (remember WCROC?), one of which seems to have had an uncomfortable encounter with a larger relative:

Science shall blossom from their demise.

The end.

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