May 24, 2013
April 27, 2013
A few weeks ago I threw this picture into the “Night at the Museum” post and promised to say more later. Later is now.
I started sculpting dinosaur claws because of the coincidental arrival of two things in my life. One was a cast of OMNH 780, the horrifically awesome thumb claw of Jurassic megapredator Saurophaganax maximus, which I blogged about here. (If you’re curious, I’m using it to amaze people at public talks, so it is serving a semi-legit educational purpose.)
The other is this video of Adam Savage’s TED talk on how he got into sculpting two very different birds. I’ve watched it about a zillion times and shown it to loads of friends, because Savage so nicely captures what it’s like to be obsessed by interesting things. We have different objects of desire, and, okay, I don’t have 20 gigs of photos of anything, but when I’m having a lousy day, watching that video reminds me why I do what I do. You should blow off the rest of this post and go watch it right now.
Back so soon? So, I am a little obsessed with theropod claws right now (aesthetically and fanboyishly, not scientifically), and I thought it would be cool to try my hand at making them. Also, I’ve been wanting to do some molding and casting, and I wanted to be able to practice on cool stuff without having any ethical concerns about trading in fossils or replicating someone else’s specimen. More on the molding and casting in a future post.
A final boring note before the actual instructions: I have no idea what I’m doing. Those two claws in the photo above? The little one on the right is the first thing I’ve sculpted out of anything more serious than Play-Doh, and the big one on the left–the subject of this post–is the second. If I can do this, you can do this.
On to the how.
Sculpey isn’t really clay in the traditional sense. It’s slightly oily plastic that polymerizes when baked. When it first comes out of the package, it’s surprisingly brittle and crumbly. You have to knead it for a while before you can do anything useful with it.
Here’s a lump after some kneading. My work surface here is a dinner plate covered with aluminum foil.
At the local hobby store you can buy a set of clay sculpting tools, in plastic for about five bucks or in wood for up to thirty. But unless you’re a professional sculptor you can skip all that folderol and just use your fingers and crap you find around the house.
The main thing I learned during this stage? You can achieve just about any shape you want, depending on how much time you’re willing to invest. I worked iteratively, smoothing and resmoothing and smoothing some more.
Cheap tools in action: using popsicle sticks to smooth the edges of the claw. You can get a bag of 100 of these suckers at the dollar store. If you don’t already have a decent pair of wire cutters, you can get them at the dollar store, too, and you can use the wire cutters to cut all kinds of edges into the popsicle sticks. So that’s like 100 clay tools for a buck or two.
If it seems like I’m hating on fancy clay tools, it’s because IME real artists just get on with making art and don’t get too precious about it. Here’s Zak Smith on painting (warning–nothing bad in that post, but there is some NSFW stuff elsewhere on that site):
the process is as follows: I take a very small paint brush with wet paint on it, put it on the paper, and move my hand around. There is no magic or machinery involved and it is done freehand. Sometimes I look at a real thing or person and paint it, sometimes its a picture i took, and sometimes i just make it up. How to tell? If its a picture with a title like “Lisa” then probably that’s from real life, if it’s, say, a zebra-man with two samurai next to it, then that’s made up.
“What kind of paint?” The cheapest kind they have at whatever store I am at.
So it drives me crazy when I see wannabe artists shelling out thirty bucks for tools they could make or emulate for less than a tenth of that. (If you’re serious enough to have actual fancy tools, holster the angry comments, I don’t think you’re keeping the local Hobby Lobby in business buying the faux-fancy tools.)
Need a clay knife? Floss picks work pretty well. I used this one a LOT. Here I’m angling the articular facet for the next phalanx.
Blood vessel grooves. I think I used the blunt end of a bamboo kabob skewer to install these, with some follow-up shaping with popsicle sticks. I also straightened and shortened the claw tip a bit from the previous photo.
Funny story: a few years ago I was going through the public exhibits at a certain nameless museum and at the “touch a fossil” table an excited young docent started to explain how the “blood groove” was there to let the blood flow out of the wound so the claw wouldn’t get trapped by suction. I tried to explain that it was really there to hold the vessels that nourished the keratin sheath that covered the bony claw in life, but he was unpersuaded. I wished, for the first and only time, that I had a cast Tenontosaurus claw with me so he could explain why herbivores needed “blood grooves” on their claws, too…
Now: detailing. I didn’t want to sculpt the claw as it was in life, I wanted a fossil claw, something that looked like it might have been left out in the rain for 145 million years. The bone I picked up on the beach, and the exposed spongiosa is just perfect for putting a realistic bone texture on stuff. The rock is a rock. I used it for nicks and gouges.
I carve cracks with a straight pin. I carve them fairly deep, a couple of mm, so if I accidentally smudge some clay over a crack I can cut or sand it off, post-baking, and get the crack back. I don’t worry about raised edges along the edges of the cracks–these sand off in a heartbeat after baking. Just carve away.
Right after the above photo was taken, I popped the whole plate in the oven for about 45 minutes at 295 F to bake the Sculpey. There are lots of different kinds of Sculpey and other polymer clays on the market, so read the instructions on the box before you bake. Also, the baking drives off the oils that made the stuff kneadable, so save your baking for a nice day when you can have the windows open. If you’re going to bake a lot of Sculpey, you might want a separate oven for it. The vapors from the baking Sculpey do make me feel a little ill, so I get some good airflow through the house and limit my exposure. Caveat sculptor.
Here’s the claw right after baking. Some areas are smooth and shiny from being in more intimate contact with the foil. If you’re not going to sculpt the other side of something and you want a perfectly flat, smooth surface, watch out for this.
The only point of this photo is to show that the baked Sculpey is not rock-hard. The tip of the claw is drooping under its own weight here. For my first, smaller claw, I carved a groove in the flat side with a Dremel and put in a section of bent hanger wire to help it maintain its shape. For this second one, I figured the other half of the claw would give it sufficient thickness to hold its shape after baking, and I was right.
Here’s the reverse side, sculpted using the same techniques as I used for the first side, but not baked yet. I suppose there might be some kind of Sculpey Einstein out there who can do a whole claw in one go, but I couldn’t figure out how to do both sides without leaving fingerprints everywhere, or how to support the thing while it baked, so I did the two sides sequentially. If you think of a better solution, let me know, although really this is not much extra work–about an hour, max, while I was watching Mythbusters.
Now we gotta talk about asbestos for a while (this is relevant, I promise). Here’s a photomicrograph of a macrophage (a kind of white blood cell) self-impaled on some asbestos fibers, in what started out as attempted consumption of foreign material by the macrophage, and ended up closer to a crucifixion.
Here’s the deal: you have macrophages roaming around in your lungs, and when they find stuff that isn’t supposed to be there–which is pretty much everything other than your own living cells–they eat the offending material. And by “eat” I mean “engulf and try to chemically destroy”, using all kinds of profoundly noxious stuff–hydrochloric acid, hydrogen peroxide, chlorine gas. And if the offending material is extremely resistant to such treatment, as is the case with asbestos, the macrophages just keep unleashing hell. Forever. Which doesn’t dissolve the asbestos, but does eventually dissolve your lungs. Asbestos by itself doesn’t hurt you much–it’s what you do to yourself trying to get rid of it that kills you.
Why am I bringing up this depressing stuff? Partly because you are in command of a human body and you should know something about how it works. And partly because, if you have been following this little how-to, very soon you are going to be sanding your Sculpey dinosaur claw. Which is made out of plastic. Which is going to shed tiny particles of plastic into the air while you sand it. Which you are going to inhale unless you are wearing a mask. Now, I don’t know the actual resilience of baked Sculpey particles under the chemical assault your macrophages are prepared to light them up with, and I don’t recommend that you perform the experiment on yourself. I got a pack of five of these:
for two bucks at the hardware store. If you can afford ten bucks for a block of Sculpey, you can afford to spend two more to save your lungs.
This goes for sanding just about everything, by the way. It’s like germs or radiation, just because you can’t see or feel the damage doesn’t mean that it isn’t happening. Also like germs and radiation, some simple precautions are all you need to avoid the vast majority of the problems. Or you can skip them, and someday someone like me may be using your corpse to teach people about how not to care for a human body. Your pick!
Sanding. I only do one pass, with 220 grit. If you start with 60 grit, you can say goodbye to all the details you put in, because they are going to be gone very quickly. Basically I’m just trying to knock off the most egregious of the rough edges. I’m not trying to get a very smooth surface–that comes next.
I didn’t take any pictures of this, but after the sandpaper I scrubbed the whole claw with 000 steel wool. I had never used this stuff before–I only learned about it from that Adam Savage TED talk–and it is pretty amazing. For one thing, it will give whatever you are sanding a shockingly smooth finish. For another, it actually goes away as you use it. You’ll start out with a full-sized bundle and after sanding for 10 minutes you’ll be down to a half-size bundle. If you’re slouching in front of the TV, it will look like a metal cat shed all over your t-shirt. The chances of actually inhaling a tiny sliver of steel and having it get all the way down into your lungs are probably pretty slim, but I masked up anyway (there are still microscopic Sculpey shards coming off at this stage). Anyway, the steel wool gives a very even appearance to the surface, so you can’t tell what areas got really hit by the sandpaper, and for me it was one of the most satisfying parts of the whole process.
And here’s the final result. On the right the tip is a little blackened from over-baking, since the right side went through the oven twice, but it’s not bad. At this point you can paint or do whatever. I haven’t experimented with painting Sculpey yet, and online sources are mixed about what works best. You don’t want to use anything thick for a primer or you’ll lose the fine details. When I do finally get around to painting, I’m going to start with flat black auto primer, just like Adam Savage used on his Maltese Falcon (which I know was resin, not Sculpey, but still), and see if that doesn’t do the trick. If you know of something better, please tell us in a comment.
Next up in this series: molding and casting.
April 26, 2013
Earlier this spring London and I got on a building dinosaurs kick, inspired by this post at Tumblehome Learning. I used a few of these photos as filler in this post, but I haven’t talked much about what we did and what we learned.
Above is my first attempt at a wire skeleton for a papier mache dinosaur. Yes, despite being a dino-geek from the age of three on, I had never made a papier mache dinosaur before this spring. The thicker white wires are from a hanger, and the thin ones are from a reel of wire I found in the hardware section at Wal-Mart. It’s held together with masking tape, and the thick wires running down the legs of the dino are going into holes I drilled in that piece of scrap wood.
Here’s part of the wireframe for my first skull. At this point I was still thinking of Alioramus. Notice the sections of drinking straw, split and popped onto the wires to bulk out the wireframe and give the papier mache more than a 2D plane to bite on.
Here’s that lower jaw with the rest, a skull of some kind of predatory coelurosaur. Fairly early on I abandoned the strict Alioramus plan and followed in the footsteps in Barnas Monteith at Tumblehome Learning (who posted the instructions linked above) in going for a sort of generic critter instead of any particular real-life taxon. Therefore, I was free to freewheel without having to worry too much about accuracy (Robert Frost would have said I was playing tennis with the net down). As you can see here, this is another wire job held together with duck tape, and the lower jaw already has the first layer of papier mache on.
Papier mache is pretty hard to screw up: put some water in a bowl, add flour until it gets thick, stick pieces of torn-up newspaper in the mix and put them on whatever you’re making. Anything more than that, you should learn on your own by experimentation.
Progress on “Rexy” and my skull was going too slow for London, so I knocked out a crude Velociraptor skull in cardboard for him to work on at his own pace. This became “Rapty”.
An early family portrait: “Rapty”, “Rexy”, and my “Uglioramus” skull. You can see the Wedel method for not messing up the dining room table: first, put down a layer of plastic trash bags taped together, then a layer of newspapers taped together. For Rexy, we put down a layer of cling wrap to keep the papier mache drips off the wood base, which was a huge win in the long run. Rapty and Ulgioramus are sitting on foil-covered pizza-baking sheets. Those turned out to be useful for…
…baking skulls. Papier mache dries s l o w l y in cool, wet weather. But if it will fit, you can pop your thing in the oven on low heat for 15-20 minutes and get’er done quickly. This worked for both skulls, but it worked better for Rapty. On Uglioramus, the metal expanded enough to keep poking its way out of the papier mache, so I did a lot of patching. Still probably faster than waiting for the whole thing to air-dry.
Teeth. I went a little nuts with these in terms of size (I know, those teeth won’t fit into that maxilla, but it looks rad if you switch your brain off, kind of like Jurassic Park). They’re made up of flat cardboard from a cheap box (not corrugated) layered together with wood glue to give them some thickness, and coated with more wood glue and papier mache goo to soften the contour lines.
Before painting I sealed the whole thing with a thin layer of Titebond wood glue. That probably wasn’t 100% necessary, given what went on next, but I knew it would get the job done and strengthen the structure.
Back to “Rapty”: he got a set of teeth–one layer of thin cardboard this time–entirely speculative nasal and parietal horns courtesy of London, and a couple of coats of Kilz2 white latex primer left over from a telescope-making project. Then he was off to school for show-and-tell. Since then he’s gotten one thin coat of brown watercolor paint. Some of the holes in the skull just about closed up during papier-macheing, but since the impetus for the project was to have fun, it doesn’t trouble me.
Here’s Uglioramus, also dressed in Kilz, awaiting his first coat of paint in my expensive, professional paint box. Leaving a freshly-painted object without overhead protection in this neighborhood is just asking for it to be hit by falling vegetation.
And here we are after the first coat. I use Krylon because it’s cheap, tough, and dries fast, but with the Kilz on I could probably use just about anything.
And that brings us up to the present. I have some ideas on how to finish Uglioramus to make it look more like a fossil skull and less like some cast-off from a flea market, but those will have to wait for another post.
The upshot of all of this is that I am not an expert on either theropod skulls or papier mache, and if a doofus like me can do this well the first time out, you can probably do as well or better yourself. And it’s cheap, messy fun. Highly recommended.
April 19, 2013
Up top there is a commercially obtained
cast sculpture of a thumb claw of Megaraptor. Down below is an unpainted urethane cast of one of my favorite inanimate objects in the universe: OMNH 780, a thumb claw of Saurophaganax. I dunno how much of the Megaraptor claw is real [none, it turns out, but it's based on a true story]; certainly the cast is faithful enough to record some tool-marks in the rugose part near the base. But I know how much of OMNH 780 is legit, and that is all of it. I would have put in a photo of the actual specimen but irritatingly I forgot to take any during my recent visit, and I didn’t have the Megaraptor claw back then anyway. Hopefully I’ll get back to the OMNH this summer, and then it is ON.
The kaiju-loving fanboys of CarnivoraForum undoubtedly want to know how these two compare. Well, much to my disappointment, the Megaraptor claw is a shade longer (28.7 cm max straight-line distance) than the Saurophaganax claw (26.3 cm). But the Saurophaganax claw is about twice as thick and way more robust, and the flexor tubercle which anchored the tendon that powered the claw’s movement is friggin’ immense. It’s like pitting an NBA forward against an NFL linebacker: one is a little taller, but the other one will pound you like a tent stake.
If anyone’s wondering, these claws are both waaay shorter than those of Therizinosaurus (half a meter and up), which still holds the longest-claws-of-anything-ever title. The problem for fans of excessive violence is that Therizinosaurus probably wasn’t doing terribly exciting things with its claws–grooming its feathers, making veggie kabobs, and scratching its ample behind, most likely.
The same was not true for Saurophaganax, which the unbelievers call Allosaurus maximus, a red-blooded all American murder machine with a triple PhD in kicking your ass. When it wasn’t drinking camptosaur blood straight from the jugular, it was eating mud-mired diplodocids butt first while they were still alive. And what about those rumors that Saurophaganax was completely feathered in $100 bills, or that it was the direct linear ancestor of Charles Bronson and Steven McQueen? It’s probably too soon to say, since I just made them up, but I’ll bet your mind is blown nonetheless.
How dangerous was Saurophaganax? Let me put it this way: it’s still dangerous. Thanks to the high concentration of heavy elements in Morrison dinosaur bones, you’re supposed to air out the specimen cabinets before you start working so the radon can escape. Otherwise you might breathe in freakin’ radioactive gas and get cancer (in contrast to some “facts” in the previous paragraph, this is actually true). That’s right, Saurophaganax can kill you, just by lying around in a drawer. After 145 million years, it’s still reaping souls for Hades. By god, that’s giving them what for!
In short, the thumb claw of Saurophaganax is the most impressive instrument of dinosaurian destruction I’ve yet laid eyes on. If you want to see it in context, check out the mounted skeleton at the Oklahoma Museum of Natural History in Norman.
All I want to do in this post is make people aware that there is a difference between these two things, and occasionally that affects those of us who work in natural history.
In one of his books or essays, Stephen Jay Gould made the point that in natural history we are usually not dealing with whether phenomena are possible or not, but rather trying to determine their frequency. If we find that in a particular population of quail most of the birds eat ants but some avoid them, then we know some things: that quail can tolerate eating ants, that quail are not required to eat ants, and that both strategies can persist in a single population.
This idea has obvious repercussions for paleoart, especially when it comes to “long-tail” behaviors. I dealt with that in this post, and also in the comment thread to this one. But that’s not what I want to talk about today.
Sometimes it is useful to talk about things that never happen, or that have at least never occurred in the sample of things we know of. Obviously how certain you can be in these cases depends on the intensity of sampling and the inherent likelihood of a surprising result, which can be hard to judge. If you argued right now that T. rex lacked feathers because no T. rex specimens have been found with feathers, you’d most likely be wrong; it is almost certainly just a matter of time before someone finds direct evidence of feathers in T. rex, given the number of T. rex specimens waiting to be found and the strength of the indirect evidence (e.g., phylogenetic inference, analogy: ornithomimids are known to be feathered even though most specimens are found without feather impressions). If you argue that sauropods are unique among terrestrial animals in having necks more than five meters long, you’re most likely right; being wrong would imply the existence of some as-yet undiscovered land animal of sauropod size, or with seriously wacky proportions (or both), and our sampling of terrestrial vertebrates is good enough to make that extremely unlikely.
The reason for this post is that sometimes people confuse that last argument, which is about sampling and induction, with the argument from personal incredulity.
For example, in our no-necks-for-sex paper (Taylor et al. 2011), we included this passage:
Sauropoda also had a long evolutionary history, originating about 210 million years ago in the Carnian or Norian Age of the Late Triassic, and persisting until the end-Cretaceous extinction of all non-avian dinosaurs about 65 millions years ago. Thus the ‘necks-for-sex’ hypothesis requires that this clade continued to sexually select for exaggeration of the same organ for nearly 150 million years, a scenario without precedent in tetrapod evolutionary history.
One of the reviewers argued that we couldn’t include that section, because it was just the argument from personal incredulity writ large, like so:
There are no other known cases of X in tetrapod evolutionary history, and therefore we don’t believe that the case in question is the sole exception.
…with the second part of that unstated (by us) but implied. But we disagreed, and argued (successfully) that it was an argument based on sampling, like so:
There are no other known cases of X in tetrapod evolutionary history, and therefore it is unlikely that the case in question is the sole exception.
Now, it is perfectly fair to criticize arguments like that based on the thoroughness of the sampling and the likelihood of exceptions, as discussed above for T. rex feathers. Just don’t mistake arguments like that for arguments from personal incredulity.* On the flip side, if someone makes an argument from personal incredulity, see if the same thing can be restated as an argument about sampling. Maybe they’re correct but just expressing themselves poorly (“I refuse to believe that the moon is made out of cheese”), and maybe they’re wrong and restating things in terms of sampling will help you understand why.
* If you want to get super pedantic about it, they’re both arguments from ignorance. But one of them is at least potentially justifiable by reference to sampling. Absence of evidence is not necessarily evidence of absence, but it may get to be that way as the sampling improves (e.g., there is no evidence of planets closer to the sun than Mercury, and at this point, that is pretty persuasive evidence that no such planets exist).
Parting shot: one thing that has always stuck in my head from Simberloff (1983) is the bit about imagining a large enough universe of possible outcomes. And I’ve always had a perverse fascination with Larry Niven’s “Down in Flames”, in which he pretty much demolished his Known Space universe by assuming that every basic postulate of that universe was false. Neither of these follow directly on from the main point of the post, but they’re not completely unrelated, either. Because I think that they yield a pretty good heuristic for how to do science: imagine what it would take for you to be wrong–imagine a universe in which you are wrong–and then go see if the thing that makes you wrong, whatever it is, can be shown to exist or to work. If not, it doesn’t mean you’re right, but it means you’re maybe less wrong, which, if we get right down to it, is the best that we can hope for.
The photos have nothing to do with the post, they’re just pretty pictures from the LACM to liven things up a little.
- Simberloff, D. (1983). Competition theory, hypothesis-testing, and other community ecological buzzwords. The American Naturalist, 122(5), 626-635.
- Taylor, M. P., Hone, D. W., Wedel, M. J., & Naish, D. (2011). The long necks of sauropods did not evolve primarily through sexual selection. Journal of Zoology, 285(2), 150-161.
April 10, 2013
This is a caudal vertebra from the middle of the tail of an ostrich, LACM Bj342:
The middle row shows it in anterior, left lateral and posterior views; above and below the anterior view are the dorsal and ventral views. It’s about 5 cm across the transverse processes. (This figure is from a manuscript that Matt and I will submit to a journal probably within 24 hours.)
In compositing the different views, I had a heck of a time recognising what was what. The dorsal view looks so much more like what we’d expect a ventral view to look like — indeed, the two are more similar for this vertebra than for any other I’ve seen.
How about those big pnuematic foramina right at the top of the bone? At first, Matt and I thought we’d never seen anything like that before. But then we realised that we sort of had — in a cervical vertebra of Apatosaurus which appears as part one of Taylor and Wedel (2013: figure 9).
This is Apatosaurus sp. OMNH 01341 in right posterodorsolateral view. “las” marks a ligament attachment site — a big, baseball-sized rugose lump — and right next to it is a pneumatic foramen, marked “pfo”.
Just like this, the ostrich caudal is a saurischian vertebra with a bifid neural spine, and with pneumatic foramina within the intermetapophyseal cleft.
April 8, 2013
Last night London and I spent the night in the Natural History Museum of Los Angeles County (LACM), as part of the Camp Dino overnight adventure. So we got lots of time to roam the exhibit halls when they were–very atypically–almost empty. Above are the museum’s mounted Triceratops–or one of them, anyway–and mounted cast of the Mamenchisaurus hochuanensis holotype, presented in glorious not-stygian-darkness (if you went through the old dino hall, pre-renovation, you know what I mean).
We got there early and had time to roam around the museum grounds in Exposition Park. The darned-near-life-size bronze dinos out front are a minor LA landmark.
The rose garden was already closed, but we walked by anyway, and caught this rainbow in the big fountain.
After we checked in we had a little time to roam the museum on our own. I’ve been meaning to blog about how much I love the renovated dinosaur halls. The bases are cleverly designed to prohibit people touching the skeletons without putting railings or more than minimal glass in the way, and you can walk all the way around the mounted skeletons and look down on them from the mezzanine–none of that People’s Gloriously Efficient Cattle Chute of Compulsory Dinosaur Appreciation business. Signage is discreet and informative, and so are the handful of interactive gizmos. London and I spent a few minutes using a big touch-screen with a slider that controlled continental drift from the Triassic to the present–a nice example of using technology to add value to an exhibit without taking away from the real stuff that’s on display. There are even a few places to sit and just take it all in. That’s pretty much everything I want in a dinosaur hall.
Also, check out the jumbotron on the left in the above photo. It was running a (blessedly) narration-free video on how fossils are found, collected, prepared, mounted, and studied, on about a five-minute loop. Lots of pretty pictures. Including this next one.
There are a couple of levels of perspective distortion going on here, both in the original photo and in my photo of that photo projected on the jumbotron.
Still, I feel confident positing that that is one goldurned big ilium. I’m not going to claim it’s the biggest bone I’ve ever seen–that rarely ends well–but sheesh, it’s gotta be pretty freakin’ big. And apparently a brachiosaurid, or close to it. Never mind, it’s almost certainly an upside-down Triceratops skull. Thanks to Adam Yates for the catch. I will now diminish, and go into the West.
Triceratops, Styracosaurus, and Einiosaurus–collect the whole set!
Of course, the centerpiece of the second dinosaur hall–and how great is it that there are two!?–is the T. rex trio: baby, juvenile (out of frame to the right), and subadult. Yes, subadult: the “big” one is not as big as the really big rexes, and from the second floor you can see unfused neural arches in some of the caudal vertebrae (many thanks to Ashley Fragomeni for pointing those out to me on a previous visit).
Awwwww! C’mere, little fella!
Still, this ain’t Vulgar Overstudied Theropod Picture of the Week. Here are some sweet pneumatic diplodocid caudals in the big wall o’ fossils (visible behind Mamenchisaurus in the overhead photo above). The greenish color is legit–in the Dino Lab on the second floor, they’re prepping a bunch of sauropod elements that look like they were carved out of jade.
Sudden violent topic shift, the reason for which will be become clear shortly: London and I have been sculpting weapons of mass predation in our spare time. In some of the photos you may be able to see his necklace, which has a shark tooth he sculpted himself. Here are a couple of allosaur claws I made–more on those another time.
The point is, enthusiasm for DIY fossils is running very high at Casa Wedel, so London’s favorite activity of the evening was molding and casting. Everyone got to make a press mold using a small theropod tooth, a trilobite, or a Velociraptor claw. Most of the kids I overheard opted for the tooth, but London went straight for the claw.
Ready for plaster! Everyone got to pick up their cast at breakfast this morning, with instructions to let them cure until this evening. All went well, so I’ll spare you a photo of this same shape in reverse.
We were split into three tribes of maybe 30-40 people each, and each tribe bedded down in a different hall. The T. rex and Raptor tribes got the North American wildlife halls, but our Triceratops tribe got the African wildlife hall, which as a place to sleep is about 900 times cooler. Someone had already claimed the lions when we got there, so London picked hyenas as our totem animals.
Lights out was at 10:30 PM, and the lights came back on at 7:00 this morning. Breakfast was out from 7:15 to 8:00, and then we had the museum to ourselves until the public came in at 9:30. So I got a lot of uncluttered photos of stuff I don’t usually get to photograph, like this ammonite. Everyone should have one of these.
London’s favorite dino in the museum is Carnotaurus. It’s sufficiently weird that I can respect that choice.
Not that there’s anything wrong with the old standards, especially when they’re presented as cleanly and innovatively as they are here.
Finally, the LACM has a no tripod policy, and if they see you trying to carry one in they will make you take it back to your car. At least during normal business hours. But no one searched my backpack when we went in last night, and I put that sucker to some good use. Including getting my first non-bigfoot picture of the cast Argentinosaurus dorsal. It was a little deja-vu-ey after just spending so much time with the giant Oklahoma Apatosaurus–elements of the two animals really are very comparable in size.
If you’re in the LA area and interested in spending a night at the museum–or at the tar pits!–check out the “Overnight Adventures” page on the museum’s website. Cost is $50 per person for members or $55 for non-members, and worth every penny IMHO. It’s one of those things I wish we’d done years ago.
March 11, 2013
For a paper that I and Matt are preparing, we needed to measure the centrum length of a bunch of turkey cervicals. That turns out to be harder than you’d think, because of the curious negative curvature of the articular surfaces.
Above is a C7 from a turkey: anterior view on the left; dorsal, left lateral and ventral views in the middle row; and posterior on the right. As you can see from the anterior, dorsal and ventral views, the anterior articular surface is convex dorsoventrally but concave transversely; and as you can see from the lateral view, the posterior face is concave dorsoventrally and convex transversely.
This means you can’t just put calipers around the vertebra. If you approach the vertebra from the top or bottom, then the upper or lower lip of the posterior articular surface will protrude past the centre of the saddle, and give you too long a length. If you approach from the side, the same will happen with the left and right lips of the anterior articular surface.
What are we trying to measure anyway?
But this raises the question of what it is we’re trying to measure. I said “we needed to measure the centrum length of a bunch of turkey cervicals”, but what exactly is centrum length? Why shouldn’t the upper and lower lips of the posterior articular surface count towards it?
What does centrum length mean?
The problem doesn’t only arise with bird cervicals. The same issue arises in measuring more sensible and elegant vertebrae, such as our old friend HMN SII:C8, or MB.R.2181:C8 as we must now learn to call it.
Although the back of the vertebra is nice and simple here — it’s obvious what line we’re measuring to at the back — we have three choices of where the “front” of the vertebra is, and a case can be made for any of them as being “the length of the vertebra”.
The longest measurement (here marked “T” for “total length”) goes to the front of the prezygapophyseal rami. The next one (“C” for “centrum length”) goes to the anteriormost point of the condyle. The distinction is important: as noted recently, the longest vertebra in the world belongs to Sauroposeidon if we use total length, but to Supersaurus if we use centrum length.
But in life, most of the condyle would be buried in the cotyle of the preceding vertebra. So should it count towards the length of the vertebra? If you consider a string of articulated vertebrae, the buried condyles don’t contribute to the overall length of the neck. So Matt and I call the length from the posterior margin of the condyle to the posterior margin of the cotyle the functional length (marked “F” above), which I believe is a new term.
Another way to think of the functional length is the distance from a given point on a vertebra (in this case the posterior margin of the cotyle) to the same point on the adjacent vertebra:
For our current project, Matt and I are interested in how the lengths of individual vertebrae contribute to total neck length, so for our purposes, functional length is definitely what we want.
By the way, Janensch is the only author I know of to have even recognised the importance of functional length. The measurement tables on pages 39 and 44 have columns for “Gesamtlänge des Wirbels ab Vorderende per Präzygapophyse”, “Gesamtlänge der Wirbel-Körpers in 1/2 Höhe” and “Länge der Wirbel-körpers ohne Condylus in 1/2 Höhe” — that is, ”Total length of the vertebra from the anterior end of the prezygapophysis”, “Total length of the centrum measured at mid-height” and “Length of the centrum minus condyle at mid-height”. This is typical of his careful and methodical approach. Kudos!
Hey! I thought this was about turkeys
And so it is. Here is the functional length measurement for a turkey cervical:
It’s the shortest anteroposterior distance between the two articular surfaces.
Measuring functional length
Matt and I chatted about this at some length, and I am ashamed to say that we thought through all sorts of complicated solution involving subtracting measurements from known scaffold length and suchlike.
It took us a stupidly long to to arrive at the very obvious solution, which is just to modify the calipers to have a “tooth” that can protrude into the concavity of the anterior articulation between its left and right lips. Easily done with a flat-ended screw and a blob of wood glue:
With the measurements of all the vertebrae in my series, I can now fairly confidently expect that the sum of the individual lengths will come out at about the length of the complete neck.
You know, unless intervertebral cartilage turns out to be important or something.
- Janensch, Werner. 1950. Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3:27-93.
1. Matt and I are so used to opisthocoelous sauropod presacrals that when we’re talking about vertebrae — any vertebrae — we tend to say “condyle” and “cotyle” for the anterior and posterior articular surfaces, no matter what their morphology. When talking about crocodile cervicals or titanosaur caudals, we’re even likely to say ridiculous things like “the condyle is concave and the cotyle is convex”. Nonsense, of course: condyle means “A rounded prominence at the end of a bone, most often for articulation with another bone.” What we should say is “the condyle is at the back and the cotyle is in front”.
Big news yesterday. Identical bills were introduced into the US House of Representatives and Senate that, if passed, will make federally-funded research freely available within six months of publication. Here’s the exact wording, from the press release on Mike Doyle’s (D-PA) website:
The Fair Access to Science and Technology Research Act (FASTR) would require federal agencies with annual extramural research budgets of $100 million or more to provide the public with online access to research manuscripts stemming from funded research no later than six months after publication in a peer-reviewed journal.
As Peter Suber explains here and here, FASTR is a stronger version of FRPAA, the Federal Research Public Access Act, which has been introduced in Congress three times before (2006, 2009, and 2012) but never come up for a vote. However, momentum for open access is gathering, both on the supply side with progressive new outlets like eLife and PeerJ, and on the demand side of, well, citizens demanding access to the research they’ve already paid for, and legislators increasingly agreeing with them. So FASTR has a real shot at getting to a vote, and if voted on, could well pass. Which would be awesome, because we all need access.
I am especially happy that FASTR has bipartisan sponsorship in both houses of Congress. The sponsoring representatives in the House are Mike Doyle (D-PA), Kevin Yoder (R-KS), and Zoe Lofgren (D-CA). The identical Senate bill was introduced by John Cornyn (R-TX) and Ron Wyden (D-OR). So we’ve got Democrats from deeply blue states and Republicans from deeply red states, which is awesome and totally appropriate, because this issue really does cut across party lines. And, hell, last year Elsevier managed to hire bipartisan sponsorship for their toxic–in more ways than one–and rapidly-killed Research Works Act, so it’s nicely symmetrical that politicians from both sides of the aisle have come together to sponsor that bill’s near-opposite.
What can you do? If you live in the US, contact your legislators and tell them to support FASTR! It takes almost no time at all and it makes a big difference. This afternoon I called all five of the sponsoring legislators to thank them, and I called my representative and both California senators to encourage them to support the bill, and all told it took just a little over half an hour. If you skipped the thank yous and just got in touch with the legislators who represent you, it could be done in 15 minutes, and you’ve probably wasted more time than that today daydreaming about dinosaurs. Here’s what you’ll need.
Encourage your legislators:
Thank the bills’ sponsors:
- Senator John Cornyn (R-TX): (202) 224-2934
- Senator Ron Wyden (D-OR): (202) 224-5244
- Representative Mike Doyle (D-PA): (202) 225-2135
- Representative Zoe Lofgren (D-CA): (202) 225-3072
- Representative Kevin Yoder (R-KS): (202) 225-2865
This is big. This matters. Send an email, pick up the phone, make a difference.
I didn’t have any really motivational “contact your legislators!” artwork so the photos in this post are of papier mache dinosaurs–all stinkin’ theropods, I’m afraid–that I’m building with my son. More to come on that soon, but in the meantime, check this out and give it a whirl–after you contact your legislators!
January 14, 2013
My friend, colleague, and sometime coauthor Dave Hone sent the above cartoon, knowing about my more-than-passing interest in sauropod neurology. It was drawn by Ed McLachlan in the early 1980s for Punch! magazine in the UK (you can buy prints starting at £18.99 here).
I know that this isn’t the only image in the “oblivious sauropods getting eaten” genre. There’s a satirical drawing in Bakker’s The Dinosaur Heresies showing a sleeping brontosaur getting its tail gnawed on by some pesky mammals. I’ll scan that and post it when I get time. I’m sure there must be others in a similar vein–point me to them in the comments or email me and I’ll post as many as I can get my hands on.
I wouldn’t post stuff like this if I didn’t think it was funny. But if you want the real scoop on whether sauropods could have responded quickly to injuries to their distant extremities, here’s the deal:
First of all, sauropods really did have individual sensory nerve cells that ran from their extremities (tip of tail, soles of feet)–and from the rest of their skin–to their brainstems. In the longest sauropods, these cells were probably something like 150 feet long, and may have been the longest cells in the history of life. We haven’t found any fossils of these nerves and almost certainly never will, but we can be sure that sauropods had them because all vertebrates do, from hagfish on up. That’s just how we’re built. (This is all rehash for regular readers–see this post and the linked paper.)
So how long does it take to send a nerve impulse 150 feet? The fastest nerve conduction velocities are in the neighborhood of 120 meters per second, so a signal from the very tip of the tail in a 150-foot sauropod would take about half a second to reach the brain.
Is it possible that sauropods had accelerated nerve conduction velocities, to bring in those distant signals faster? To the brain, probably not. The only ways to speed up a nerve impulse are to increase the diameter of the axon itself, which some invertebrates do, and to increase the thickness of the myelin sheath around the axon, which is what vertebrates tend to do (some invertebrates have myelin-like tissues that apparently help accelerate their nerve impulses, too). Fatter axons mean fatter nerves, and for at least half the trip to the brain, the axons in question are part of the spinal cord. And we know that sauropod spinal cords were pretty small, relative to their body size, because the neural canals of their vertebrae, through which their spinal cords passed, are themselves small–Hatcher wrote about this more than a century ago. So there’s a tradeoff–sauropods could have had very fast, very fat axons, but not very many of them, and therefore poor “coverage” at their extremities, with nerve endings widely spaced, or better coverage with more axons, but those axons would be skinnier and therefore slower. We don’t know which way they went.
Incidentally, you can experiment with the density of sensory nerve endings in your own body. Close your eyes or blindfold yourself, and have a friend poke you in various places with chopsticks. Seriously–start with the two chopsticks right together, and gradually spread them out until you can feel two distinct points (or, if you want to get really tricky, have your friend mix up the close and widely spread touches so there’s no direction for you to anticipate). The least sensitive part of your body is your back–over your back and shoulders, you’ll probably have a hard time distinguishing points of touch that are less than an inch apart. On your hands and face, you’ll probably be able to distinguish points only a few millimeters apart; in fact, for fingertips you’ll probably need finer instruments than chopsticks–maybe toothpicks or pins, but I take no responsibility for any accidental acupuncture!
Back to sauropods. Could predators have taken advantage of the comparatively long nerve conduction velocities in sauropods? I seriously doubt it, for several reasons:
- Simple reflex arcs are governed by interneurons in the spinal cord. The tail-tip-to-spinal-cord distance was a lot shorter than the tail-tip-to-brain route. Even over the round trip of “sensory impulse in, motor impulse out”, it would have been at worst equal, and that’s assuming the nerve impulse had to go all the way to the base of the tail.* Call it half a second, max.
- It gets worse: the peripheral nerves outside the spinal cord are not limited by the size of the neural canal, so they can be more heavily myelinated, with faster conduction times. For example, each of the sciatic nerves running down the backs of your thighs is much larger in cross-section than your entire spinal cord. If sauropod peripheral nerves were selected for fast conduction, they might have been bigger and faster than anything around today.
- Half a second is not much time for a theropod to formulate a plan, especially if Step 1 of the plan is “grab 150-foot sauropod by the tail”.
- This assumes that said theropod was able to sneak right up to the sauropod without being detected. You go try that with a big wild herbivore and let me know how it works out. (Also, a big animal tolerating your presence, because you are pathetically small and weak, is not the same as it being unaware of your presence.)
- All of this assumes the theropod only went for the bony whip-lash at the tip of the tail–the fastest-moving extremity, and the least-nourishing single bite anywhere on the target. If the theropod went for a meatier bite closer to the base of the tail, it would have to sneak closer to the sauropod’s head (better chance of being spotted), and the nerve conduction delay would be shortened.
- A 150-foot sauropod would probably mass somewhere between 50 and 100 tons, and would be capable of dealing incredible damage to even the largest theropods, which maxed out around 15 tons. There’s a good reason predators go after the young, sick, and weak. Smaller sauropods would be less dangerous, but they’d also have faster tail-to-central-nervous-system-and-back reaction times.
- A theropod big enough to go after a 150-foot sauropod would also be subject to fairly long nerve-conduction delays, which would limit whatever trifling advantage it might have gotten from such delays in the sauropod.
So, although I have no doubt that in their long history together, giant theropods did occasionally tackle full-grown giant sauropods–because real animals do all kinds of weird things if you watch them long enough, and lions will take on elephants when they get desperate–I am extremely skeptical that the theropods enjoyed any advantage based on the “slow” nervous systems of those sauropods.
* Some relevant hard-core anatomy for the curious: sauropods have neural canals in their tail vertebrae, and usually far down their tails, too. But that doesn’t mean much–you have neural canals to the bottom half of your sacrum, but your spinal cord stops around your first or second lumbar vertebra. From there on down, you just have nerve roots. So the shortest reflex arc from your big toe has to go up to your lower back and return. Why is your spinal cord so short? Basically because your central nervous system stops growing when you’re still a child–it will add new connections after that, and a few new cells in your olfactory bulbs and hippocampus, but it won’t get appreciably bigger or longer. After mid-childhood, your body keeps growing but your spinal cord stays the same length, so you end up with this freaky little-kid spinal cord tucked up inside your grown-up vertebral column. Weird, huh?
So did sauropod spinal cords stop at mid-back or go all the way into the tail? We have several conflicting lines of evidence. In extant reptiles, the spinal cord does extend into the tail in at least some taxa (I haven’t done anything like a complete survey, just read a couple of papers). Birds are no help because their tails are extremely short, but their spinal cords do extend into the synsacrum (and expand there, thanks to the glycogen body, which was probably also present in sauropods and responsible for the inaccurate “second brain” meme). But then birds grow up very fast, with even the largest reaching full size in a year or two, so they don’t share our problem of the body outgrowing the nervous system. We know that sauropods grew pretty quickly, but they also took a while to mature–somewhere between one and three decades, probably. Did that protracted growth period give their vertebral columns the time to outgrow their spinal cords? I have no idea, because the division of the spinal cord into roots happens inside the dura mater and doesn’t leave any skeletal traces that I know of. Someone should go figure it out–or at least figure out if it can be figured out!