January 10, 2014
I made these back in the day. The idea was that you could print them out and have them along while dissecting bird necks, so you could draw on the muscles.
It’s basically one drawing of an ostrich vertebra, morphed in GIMP and stacked to simulate articulation. All of the ones in this post show the vertebrae in left lateral view. If you need right views, flip ‘em in GIMP or heck, I think even Windows Explorer will do that for you. The one above has dorsal views in the top row, lateral view in the middle row, and ventral views in the bottom row.
Here’s a sheet with two rows in lateral view, the idea being that you draw on the more superficial multi-segment muscles on one row, and the deeper single- or two-segment muscles on the other row.
A version with 12 vertebrae, so you can map out the often complicated patterns of origins and insertions in the really long muscles. How complicated? Well, check out this rhea neck with the M. longus colli dorsalis and M. longus colli ventralis fanned out.
That’s all. Have fun!
December 18, 2013
When we last left my better half, Dr. Vicki Wedel, she was helping to identify a Jane Doe who had been dead for 37 years by counting growth rings in the woman’s teeth. That case nicely illustrated Vicki’s overriding interest: to advance forensic anthropology by developing new methods and refining existing ones. To that end, for the past few years she has been working with her PhD advisor, Dr. Alison Galloway at UC Santa Cruz, to revise and update Alison’s 1999 book, Broken Bones: Anthropological Analysis of Blunt Force Trauma. The revised and much expanded (504 pages vs 371) second edition, co-edited by Vicki and Alison, came out Monday (Amazon, Amazon.co.uk).
You can read the whole table of contents on Amazon (click to look INSIDE!), but the short short version is that the book has three major sections. The first covers the science and practice of trauma analysis (pp. 5-130), and the second classifies hundreds of common fractures throughout the skeleton, with illustrations (pp. 133-313). The chapters in these sections were all written by Vicki, Alison, and another of Alison’s former students, Dr. Lauren Zephro, solo and in varying combinations. Lauren, whom I always think of as “the Amazon cop”, is a 6-foot blackbelt forensic anthropologist for the Santa Cruz County Sheriff’s Office. If push came to shove I have no doubt that she could beat me to death with her bare hands and then produce a technical analysis of my corpse.
The final section (pp. 314-410) consists of nine case studies contributed by forensic anthropologists, pathologists, medical examiners, forensic and medical artists, and a DoD casualty analyst, based across the Anglophone world from Hawaii to Scotland. There’s some grim stuff in there: trauma to the homeless and elderly, from intimate partner violence, and from child abuse. It’s gut-churningly awful that the defenseless suffer from bone-breaking violence; it’s always been amazing to me that people like Vicki, Alison, Lauren, and the other contributors have both the courage to face these horrors and the technical chops to make the unspeakable solvable.
Beyond that unavoidable darkness, if you’re interested in the many, varied, and often just plain weird ways in which people die, the book is a treasure trove. There’s an elderly woman lying on her deathbed for six years, slowly turning into a natural mummy… (wait for it) …while her daughter went on living in the same house. There’s a classification of plane crashes with a description of what human remains will be found and over what area. There are people hit by trains; the funniest line in this very serious book is the deadpan and unsurprising, “The typical pedestrian hit by a train is male and often highly intoxicated.”
That’s from the top of page 122. At the bottom of the same page is my one contribution to the book, which also appears as the cover art (yeah, nepotism, whatcha gonna do). There’s a story behind this. This guy–yes, male, dunno if he was intoxicated–was hit by a train and his head was sheared in half, with the somewhat fractured but mostly intact facial skeleton separated by a lot of missing bone from the occipital region. With no way to obtain the deceased guy’s permission to use his mortal remains in the book, Alison and Vicki didn’t feel comfortable including their photos, so I spent a weekend bashing out a technical drawing for them to use instead. That reawakened my interest in pen-and-ink work and led to the dödö pöst.
I should say two things right here: first, that yes, I am hijacking the rest of the post to talk about myself. (Is anyone really surprised? I thought not.) Second, that I have had no training and possibly my stippling violates Art Rules or best practice guidelines of which I am ignorant. But I hope it also illustrates what can be achieved in a couple of days, with about $15 worth of supplies, by a guy whose only rule is “möre döts”.
So anyway, if you’re curious, here’s the method I use for my pen-and-ink illustrations:
- Get a decent-sized photo of the object to be drawn. I usually roll with $2 8x10s from MalWart, in this case one for each half of the skull.
- Tape the photo down to your work surface. I have a large, incredibly hard, perfectly smooth cutting board that I use for this, but in a pinch you could use just about anything, including just a larger piece of paper. Cardboard off the backs of desk calendars is nice.
- Over the photo, tape down a piece of tracing paper.
- Lightly trace the outline of the photo and all the major details in pencil.
- Once you’ve gone as far as you can with that, peel up one side of the tracing paper, unstick the photo from the work surface, and remove it. Stick the tracing paper back down the work surface.
- Using the uncovered photo as a reference, pencil in any other salient details by eye. Also contour lines for shadows. All of the pencil lines are going to be erased later, so don’t be shy.
- Whenever you decide you’re done with the pencil, get a good pen and start tracing, directly over the pencil lines. I tend not to be too persnicketty about my tools but decent pens are a real help here. For these recent works, I picked up a three-pack of beige-tubed Micron pens for $7 (this set).
- In all of the following pen-related steps, be careful to keep your big stupid hand and arm off the wet ink you just laid down–one careless smear can ruin a few hours’ work. Having a work surface that you can rotate is nice, so your pen hand can approach the drawing from any angle. Anytime I have to lay my hand on the drawing, I put down a piece of clean scrap paper first. Even if the underlying ink is dry, it just feels like a smart precaution.
- Once the lines are on, add döts to taste. With a little experimentation, you can get patterns of dots to not only indicate light and dark but also suggest textures. Different pen tips and amounts of pressure will yield dots of different sizes, which can also be useful. Dense, overlapping dots can produce an effect similar to scratchboard. BTW, sometimes I do “gear down” and place each dot with thought and care, but in the dense sections I just rat-a-tat-tat like a Lilliputian jackhammer. Try different speeds and see what you can tolerate.
- When you’re done dötting, at least to a first approximation, and you’re dead certain the ink is all dry, get a decent eraser and erase all of the pencil lines. I used one of those clicky mechanical erasers because it was cheap and soft enough to not tear up the paper.
- Re-ink any lines lightened by the erasing. I find that the döts are usually unaffected, but lines are often knocked down a bit by the eraser work. I suppose it would be cleaner to just draw natively in pen, with no prior pencilling and therefore no erasing, but the few times I’ve tried it, it hasn’t gone well. YMMV. If you’re drawing a 3D solid, this is a good time to employ an old illustrator’s trick, which is to make the bottom outline heavier and darker than the rest, to subtly convey a sense of weight.
- Scan, touch up as needed in GIMP, post to blog, bask in self-admiration.
In this case I had a few more steps, which consisted of making variants of the drawing and test-driving them by Vicki and Alison so they could pick their favorites.
This is just embarrassing: after scanning the two drawings and doing a little touch-up, I just scooted them together until they looked like a skull. The problem is that the occiput is nowhere near anatomical position. See that flange of bone above the ear-hole, pointed down and right at a 45-degree angle? That’s the back end of the zygomatic arch, and it should be aimed at the forward stump of the arch, which is just down and back from the eye socket.
Here’s the B version, where I was working entirely off of the zygomatic arch ends, and trying to get the skull into anatomical position. Scientifically this is probably the best variant I produced (I’m not claiming it’s the best possible), but aesthetically it’s a little crowded.
I’ll spare you versions C-E, all of which just scooted the back end of the skull around in an attempt to find a balance between scientific and aesthetic concerns. Here’s the winning F version, which got used for the figure, and became the seed variant for the cover.
For the cover, we tried a lot of things, including the white skull on a black background, and one that was simply inverted from the figure. By this point the publisher had sent Vicki some test versions of the cover, and I thought it would be cool if the drawing was in the same color as the cover text, so I sampled that color from the publisher’s sample cover image and applied it to all of the drawn bits. They knocked it down a few tones for the printed version, so happily it’s not this garish.
Incidentally, I had never tried to replace a bunch of discontinuous areas of the same color with another color in GIMP, so I had to look it up. The two key steps are Select > By color, with the threshold set to zero (or not, if you want to grab a bunch of related colors at once), and “Fill whole selection” in the Bucket tool. Hat tip to this dude and his commenters.
One last step: I thought the bare, unfilled yellow version looked too flat, so I tried different levels of fill to make the skull pop out from the background. I didn’t use bucket fill here–too fiddly with so many dots and edges. Instead I created a new layer of solid yellow and dropped the opacity to 17%. Then went to the drawing layer and used the magic wand tool to select the whole non-skull background. Then popped back to the yellow layer and cleared that selection, leaving yellow fill only in the boundaries of the skull outline. I also tried 10% and 25% opacity for the fill layer, but 10% was too subtle and 25% was starting to swamp some of the detail in the drawing. Between goofing around with colors and opacity levels we went through 10 versions at this stage, of which the one above is the ultimate champion.
So, that’s how the cover art came to be. Back to the book. There’s a bibliography with 1237 references (Vicki knows), and an index. The book is hardbound, with a printed cover and no dustjacket, and IMHO reasonably priced at $65, currently a few bucks less on Amazon. You probably already know whether you want a copy. If so, do the right thing–it’s not too late to get it by Christmas.
November 8, 2013
One aspect of sauropod neck cartilage that’s been overlooked — and this applies to all non-avian dinosaurs, not just sauropods — is the configuration of the cartilage in their necks. It’s not widely appreciated that birds’ necks differ from those of all other animals in this respect, and we don’t yet know whether sauropods resembled birds or mammals.
Here’s a classic sagittal view of a mammal neck — in this case a human — from The Basics of MRI (Joseph P. Hornak, 1996-2013):
You can see two distinct kinds of structure alternating along the neck: the big, square ones are vertebral centra (slightly hollow at each end), and the narrower lens-shaped ones are the intervertebral discs.
In mammals, and most animals, we find this distinct fibrocartilaginous element, the disc, between the centra of consecutive vertebrae. These discs have a complex structure of their own, consisting of an annulus fibrosus (fibrous ring), made of several layers of fibrocartilage, surrounding a nucleus pulposus (pulpy centre) with the consistency of jelly.
But in birds, uniquely among extant animals, there is no separate cartilaginous element. Instead, the articular surfaces of the bones are covered with layers of hyaline cartilage which articulate directly with one another, and are free to slide across each other. The adjacent articular surfaces are enclosed in synovial capsules similar to those that enclose the zygapophyseal joints. You can see this in the hemisected Rhea neck from last time:
The difference between these two constructions is very apparent in dissection: in birds, adjacent vertebrae come apart easily once the surrounding soft tissue is removed; but in mammals, it is very difficult to separate consecutive vertebrae, as they are firmly attached to the intervening intervertebral disc.To complicate matters further, thin articular discs occur in the necks of some birds — for example, the ostrich (see illustration below), the swan, and the king penguin. But these discs do not occur in all birds — for example, they are absent in the turkey and the rhea. When they are present, these articular discs divide the synovial cavity and prevent the (cartilage-covered) bones on either side from ever articulating directly with each other, just like the articular discs in the human temporomandibular and sternoclavicular joints. These discs are thinner than the true intervertebral discs of mammals and crocodilians; and they are different in composition, lacking the annulus/nucleus structure and consisting of a simple sheet of fibrocartilage.
Crucially, the extant phylogenetic bracket (EPB) does not help us to establish the nature of the intervertebral articulations in sauropods, as the two extant groups most closely related to them have different articulations. As noted, birds have synovial joints; but crocodilians, like mammals, have fibrocartilaginous intervertebral discs. So their most recent common ancestor, the ur-archosaur, could equally have had either condition, and so could its various descendants.
This seems like a mystery well worth solving. For one thing, in the wholly inadequate database that we assembled for the paper, the birds had much thinner cartilage than the other animals. Since they are also the only animals with synovial neck joints, thin cartilage correlates with this kind of joint — at least across that tiny database. Is that correlation reliable? Does it hold out across a bigger sample? Is there a causation? If so, then finding out what kind of intervertebral joints sauropods had would help us to determine how thick their cartilage was, and so what their actual neutral posture was.
But we can’t tell this directly unless we find sensationally well preserved specimens that let us see the structure of the cartilage. We might speculate that since birds have unique saddle-shaped joints and sauropods have ball-and-socket joints like those of mammals and crocs, they’d be more likely to resemble the latter in this respect, too, but that’s rather hand-wavey.
Can we do better?
If we can, it will be through osteological correlates: that is, features of the bones (which are preserved in fossils) that are consistently correlated with features of the soft tissues (which are not). We’d want to find out from analysis of extant animals what correlates might exist, then go looking for them in the bones of extinct animals.
A couple of times now, I’ve pitched this as an abstract for a Masters project, hoping someone at Bristol will work on it with me as co-supervisor, but so far no-one’s bitten. Maybe next year. It would be a very specimen-based project, which I’d think would be a plus in most people’s eyes.
Anyway, the awful truth is that at the moment we know spectacularly little about the cartilage in the necks of sauropods. We don’t know whether they had true intervertebral discs. If not, we don’t know whether they had articular discs like those of ostriches. We don’t know how thick these elements, if present, were. We don’t know how thick the hyaline cartilage on the bones’ articular surfaces was, or how evenly it covered its those surfaces.
And until we know those things, we don’t really know anything about neck posture or range of movement.
There’s lots of work to be done here!
February 6, 2013
Continuing the recent theme. We’re not giving this a “Things to Make and Do” header because the spirit of that category is to showcase anatomical preparations that average people could do in the comfort of their own homes and gardens (provided they can get hold of dead wallabies, bear skulls, etc.), and freezing and band-sawing a horse is probably outside that envelope for almost everyone (I hadn’t though of that when I posted the gator!).
In the spirit of MYDHHH:
This ain’t mine, it’s a teaching specimen from our vet school, which has a no-kill policy. All of the animal cadavers used in the anatomy labs are donated by the owners at the ends of the animals’ natural lives. So no animals were harmed in the making of this science.
But I wish it was mine. And as long as I’m dreaming, I’d like a pony. Anyone want to go halvesies?
January 24, 2013
Okay, before some wag makes this point, the gator is missing a good chunk of its tail, so this is more like the left half of the anterior two-thirds of a gator. But that would make a lousy title.
We might have more to say about this in the future, but for now, I’m going to let this 1000-word-equivalent speak for itself.
Many thanks to Elizabeth Rega for the use of the gator.
March 14, 2012
Another picture from the recent ostrich dissection (click for full-size, unlabeled version). Last time we were in the middle of the neck, looking from anterior to posterior. This shot is from closer to the base of the neck, looking from posterior to anterior. A lot of the stuff is the same: the ragged cut from the saw at the meat processing plant where the ostrich was cut up; the spinal cord with the supramedullary airways above it in the neural canal; and the large interspinous ligament with diverticula on either side. We’ll have reason to refer back to some of those things in the not-too-distant future, but right now I want to draw your attention to something else: the tendons of the paired longus colli dorsalis muscles toward the top of the photo.
Here’s a modified version of Wedel and Sander (2002: fig. 2) with the course of the longus colli dorsalis highlighted in red (anterior is to the left). It is a curious aspect of bird necks that the large dorsal muscles do not insert on the neural spines but on the epipophyses (or dorsal tori or dorsal tubercles) above the postzygs. A naive approach based on beam theory would suggest that inserting on the neural spines would give those muscles more leverage, but necks are tricky and often defy such a priori predictions.
Instead of inserting on the neural spines, the longus colli dorsalis muscles originate from them, especially in the posterior part of the neck, and that’s what the photo at the top shows. From the reader’s point of view, the big interspinous ligament runs forward to attach to the posterior side of the neural spine (not visible because it’s buried in gloop, but it’s about a third of the way down from the top). The longus colli dorsalis tendons are running forward from the anterior side of the neural spine.
Here’s the same thing again, also in an ostrich, but in an MRI this time (and with anterior to the right; Wedel et al. 2000: fig. 20). The dark streaks running forward from the neural spines are those longus colli dorsalis tendons. The interspinous ligament also shows up nicely as a series of white bands connecting adjacent neural spines.
- Wedel, M.J. 2005. Postcranial skeletal pneumaticity in sauropods and its implications for mass estimates; pp. 201-228 in Wilson, J.A., and Curry-Rogers, K. (eds.), The Sauropods: Evolution and Paleobiology. University of California Press, Berkeley.
- Wedel, M.J., R.L. Cifelli and R.K. Sanders. 2000. Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon. Acta Palaeontologica Polonica 45(4): 343-388.
March 10, 2012
Those ostrich necks I went to Oro Grande to get last Thursday? Vanessa and I started dissecting them last Friday. The necks came to us pre-cut into segments with two to three vertebrae per segment. The transverse cuts were made without regard for joints so we got a bunch of cross sections at varying points through the vertebrae. This was fortuitous; we got to see a bunch of cool stuff at the cut faces, and those cut faces gave us convenient avenues for picking up structures and dissecting them out further.
In particular, the pneumatic diverticula in the neck of this ostrich were really prominent and not hard at all to see and to follow. The photo above shows most of the external diverticula; click through for the full-resolution, unlabeled version. The only ones that aren’t shown or labeled are the diverticula around the esophagus and trachea (which had already been stripped off the neck segments, so those diverticula were simply gone), those around carotid arteries, which are probably buried in the gloop toward the bottom of the photo, and the intermuscular diverticula, of which we found a few in parting out the dorsal and lateral neck muscles.
There is one final group of diverticula that are shown in the photo but not labeled: the interosseous diverticula that fill the air spaces inside the bone.
We have tons of cool photos from this dissection, so expect more posts on this stuff in the future.
For previous posts showing diverticula in bird neck dissections, see:
Things to Make and Do, part 7b: more fun with rhea necks (admittedly, not the most creative title ever)
February 20, 2012
An important new paper is out:
R. Kent Sanders and Colleen G. Farmer. 2012. The pulmonary anatomy of Alligator mississippiensis and Its similarity to the avian respiratory system. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology (advance online publication). doi:10.1002/ar.22427
(It’s paywalled, naturally, but let’s just assume that everyone who reads this blog is affiliated with a big university and has access.)
First of all, congratulations to the authors on doing this properly: publishing a proper paper (sixteen pages) to follow up their big-splash Science paper of just over a year ago. As Mickey Mortimer has shown, follow-through rates when people publish in Science and Nature are generally not at all good, and it’s always encouraging to see an exception.
Here’s the abstract:
Using gross dissections and computed tomography we studied the lungs of juvenile American alligators (Alligator mississippiensis). Our findings indicate that both the external and internal morphology of the lungs is strikingly similar to the embryonic avian respiratory system (lungs + air sacs). We identified bronchi that we propose are homologous to the avian ventrobronchi (entobronchi), laterobronchi, dorsobronchi (ectobronchi), as well as regions of the lung hypothesized to be homologous to the cervical, interclavicular, anterior thoracic, posterior thoracic, and abdominal air sacs. Furthermore, we suggest that many of the features that alligators and birds share are homologous and that some of these features are important to the aerodynamic valve mechanism and are likely plesiomorphic for Archosauria.
The main reason I want to post this (apart from the fact that it’s an important finding) is because someone had to blog David Marjanovic’s classic response on the Dinosaur Mailing List (quoted with permission, since David doesn’t have his own blog):
See, this is the kind of thing where I’m totally baffled that it wasn’t figured out a hundred years ago, or 120 or 130.
I suppose the logic that has prevented people from dissecting crocodilian lungs for so long went like this:
1) Crocodilians are reptiles.
2) So, crocodilians have reptile lungs, not mammal lungs or bird lungs.
3) What are reptile lungs like? Let’s dissect the nearest reptile and find out!
4) We’re in Europe, so let’s just take the nearest lacertid, perhaps the nearest “colubrid” and maybe the nearest viperid and cut them open.
5) <snip> <snip>
6) Hooray! We’ve figured out what reptile lungs are like!
7) Textbook describes and illustrates generic non-varanid squamate lung as “reptile lung”.
8) Everyone believes it is known what reptile lungs are like.
9) Everyone believes it is known what crocodilian lungs are like, because crocodilians are reptiles.
Ceterum censeo Reptilia esse nomen delendum.
If you must keep the name, follow Joseph Collins and restrict it to Squamata or Lepidosauria. Otherwise, destroy it. Kill it with fire.
We could draw a whole lot of conclusions from this analysis, but let’s just concentrate on one: look at animals. See how they behave. Then cut them open and see what’s inside. Don’t assume. Don’t guess. Find out. To quote the splendid motto of the Kirkcaldy Engineering Works, “FACTS, NOT OPINIONS”.
Seriously. Who’d have though there was a Science paper and an Anatomical Record paper just in cutting open an alligator and having a poke around in there? Sometimes, science doesn’t progress by paradigm shifts; sometimes it progresses just by looking at things.
November 23, 2011
Here at SV-POW! we are ardently pro-turkey. As the largest extant saurischians that one can find at most butchers and grocery stores, turkeys (Meleagris gallopavo) are an important source of delicious, succulent data. With Thanksgiving upon us and Christmas just around the corner, here’s an SV-POW!-centric roundup of turkey-based geekery.
The picture at the top of the post shows a couple of wild turkeys that frequented our campsite in Big Bend in the winter of 2007. Full story here.
If you’re wondering what to do with your turkey, the answer is GRILL IT. I use the recipe (available on Facebook) of my good friend and colleague, Brian Kraatz, who has fallen to the Dark Side and works on mammals–rabbit tooth homology, even (Kraatz et al. 2010)–but still grills a mean theropod. (In his defense, Kraatz has published on extinct saurischians–see Bibi et al. 2006.) My own adventures in turkey grilling are chronicled in this post, which will show you the steps to attaining enlightenment, or at least a larger circumference.
While you’re cooking and eating, you might as well learn something about muscles. This shot of the fanned-out longus colli dorsalis muscles in a turkey neck was the raison d’etre for this post, and turned up again with different muscles labeled in one of the recent Apatosaurus maquette review posts. Mike and I ate those muscles, by the way.
After the meal, you’ll have most of a turkey skeleton to play with. This diagram is from my other ‘holiday dinosaur’ page, which I put together for the Lawrence Hall of Science and UCMP back in 2005. That page has instructions on how to turn your pile of greasy leftovers into a nice set of clean white bones. Tom Holtz is widely acknowledged as King of the Dino-Geeks, and in kingly fashion he took the above diagram and turned the geek-o-meter up to 11. Steel yourself, gentle reader, before checking out the result here.
Speaking of bones, here’s a turkey cervical from Mike’s magisterial work in this area, which first appeared as a tack-on to a post about the holotype dorsal vertebra of the now-defunct genus Ultrasauros. The huge version of the composite photo has its own page on Mike’s website, where it is available in three different background colors. The lateral view also turned up in one of my rhea neck posts.
From the serving platter to publication: when I was young and dumb, I used a photo of a broken turkey vert to illustrate the small air spaces, or camellae, that are commonly found in the pneumatic bones of birds and some sauropods (Wedel and Cifelli 2005:fig. 11F).
I made a much better version by sanding the end off a cleaned-up vertebra, and used that in Wedel (2007), in this popular article on pneumaticity (which has instructions for making your own), and way back in Tutorial 3–only the 12th ever post on SV-POW!
Finally, it would be remiss of me not to point out that turkeys are not only readily accessible, tasty sources of anatomical information, they are also pretty interesting while they’re still alive. Don’t stare at the disgusting freak in the photo above or you might lose your will to eat. Instead, head over to Tetrapod Zoology v2 for Darren’s musings on caruncles, snoods, and other turkey parts that don’t even sound like words.
That does it for now. If you actually follow all of the links in this post, you might just have enough reading to keep you occupied during that post-holiday-meal interval when getting up and moving around is neither desirable nor physically possible. If you’re in the US, have a happy Thanksgiving; if you’re not, have a happy Thursday; and no matter where you are, take a moment to give thanks for turkeys.
- Bibi, F., Shabel, A.B., Kraatz, B.P., and Stidham, T.A. 2006. New fossil ratite (Aves: Palaeognathae) eggshell discoveries from the Late Miocene Baynunah Formation of the United Arab Emirates, Arabian Peninsula. Palaeontologia Electronica Vol. 9, Issue 1; 2A:13p.
- Kraatz, B.P., Meng, J., Weksler, M., and Li, C. 2010. Evolutionary patterns in the dentition of Duplicidentata (Mammalia) and a novel trend in the molarization of premolars. PLoS ONE 5(9): e12838. doi:10.1371/journal.pone.0012838
- Wedel, M.J. 2007. Aligerando a los gigantes (Lightening the giants). ¡Fundamental! 12:1-84. [in Spanish, with English translation]
- Wedel, M.J., and Cifelli, R.L. 2005. Sauroposeidon: Oklahoma’s Native Giant. Oklahoma Geology Notes 65 (2):40-57.
November 18, 2011
- Part 1: introduction
- Part 2: the head
- Part 4: body, tail, limbs, base, and skull
- Part 5: posture
- Part 6: texture and color
- Part 7: verdict
It is probably no surprise, given my proclivities, that I have more to say about the neck than about anything else. So unless I develop an abnormal curiosity about and mastery of, say, sauropod foot anatomy in the next few days, this will be the longest post in the series.
As with the head, the neck of the Apatosaurus maquette illustrates a lot of interesting anatomy. Some of this is unique to Apatosaurus and some of it is characteristic of sauropods in general. I’ll start with the general and move toward the specific.
As we’ve discussed before, the necks of most sauropods were not round in cross section (see here and here). The cervical ribs stuck out far enough ventrolaterally that even with a lot of muscle, the neck would have been fairly flat across the ventral surface, and in many taxa it would have been wider ventrally than dorsally.
The non-circular cross section would have been exaggerated in Apatosaurus, which had simply ridiculous cervical ribs (photo above is from this post). The widely bifurcated neural spines would also have created a broad and probably flattish surface on the dorsal aspect of the neck. The extreme width of the vertebrae and the cervical ribs created a very broad neck base. As in Camarasaurus, the base of the neck was a substantial fraction of the width of the thorax (discussed here). Consequently, the cervico-thoracic junction probably appeared more abrupt in narrow-necked taxa like Diplodocus and Giraffatitan, and more smoothly blended in Apatosaurus and Camarasaurus.
All of these features–the non-circular cross-section, the flattish dorsal and ventral surfaces, the wide neck base blending smoothly into the thorax–are captured in the Apatosaurus maquette.
The ventrolateral ‘corners’ of the neck have a ribbed appearance created by, well, ribs. Cervical ribs, that is, and big ones. In contrast to most other sauropods, which had long, overlapping cervical ribs, diplodocoids had short cervical ribs that did not overlap. But in Apatosaurus they were immense, proportionally larger than in any other sauropod and probably larger than in any other tetrapod. What Apatosaurus was doing with those immense ribs is beyond me. Some people have suggested combat, akin to the necking behavior of giraffes, and although I haven’t seen any evidence to support that hypothesis over others, neither does it strike me as far-fetched (an important nuance: giraffes use their heads as clubs, clearly not an option for the small-headed and fragile-skulled sauropods). Whatever the reason, the cervical ribs of Apatosaurus were amazingly large, and may well have been visible from the outside.
Mounted skeleton of Apatosaurus louisae in the Carnegie Museum, from Wikipedia.
Now this brings me to a something that, although not universal, has at least become fairly common in paleoart. This is the tendency by some artists to render (in 2D, 3D, or virtually) sauropods with dished-in areas along the neck, between the bony loops where the cervical ribs fuse to the centra. I am going to be as diplomatic as I can, since some of the people who have used this style of restoration are good friends of mine. But it’s a fine example of shrink-wrapped dinosaur syndrome, and it simply cannot be correct.
Adjacent cervical ribs loops in sauropods would have been spanned by intertransversarii muscles, as they are in all extant tetrapods. And outside of those single-segment muscles were long belts of flexor colli lateralis and cervicalis ascendens, which are also anchored by the cervical rib loops. All of these muscles are present in birds, and only vary in their degree of development in different parts of the neck and in different taxa. The spaces between adjacent cervical rib loops are not only not dished-in, they actually bulge outward, as in the turkey neck above.
And we’re still not done; running up through the cervical rib loops, underneath all of those muscles, were pneumatic diverticula. Not just any diverticula, but the big lateral diverticula that carried the air up the neck from the cervical air sacs at the base of the neck to the vertebrae near the head end (diverticula are reconstructed here in a cervical vertebra of Brachiosaurus, from Wedel 2005: fig. 7.2). Now, it’s unlikely that the diverticula exerted any outward pressure on the lateral neck muscles, but they were still there, occupying space (except when the muscles bulged inward and impinged on them during contraction), and with the muscles they would have prevented the neck from having visible indentations between the cervical rib loops of adjacent vertebrae.
Okay, so sauropod necks shouldn’t be dished in. But might the cervical ribs have stuck out? It might seem like the same question, only seen from the other side, but it’s not. We’ve established that adjacent cervical rib loops supported bands of single-segment muscles that spanned from one vertebra to the next, and longer, multi-segment muscles that crossed many vertebrae. But could the bony eminences of the cervical ribs have projected outward, through the muscle, and made bumps visible through the skin? The idea has some precedent in the literature; in his 1988 paper on Giraffatitan, Greg Paul (p. 9) argued that,
The intensely pneumatic and very bird-like neck vertebrae of sauropods were much lighter in life than they look as mineralized fossils, and the skulls they supported were small. This suggests that the cervical musculature was also light and rather bird-like, just sufficient to properly operate the head-neck system. The bulge of each neck vertebra was probably visible in life, as is the case in large ground birds, camels, and giraffes.
Paul has illustrated this in various iterations of his Tendaguru Giraffatitan scene; the one below is from The Princeton Field Guide to Dinosaurs (Paul 2010) and is borrowed from the Princeton University Press blog.
There is much to discuss here. First, I have no qualms about being able to see individual vertebrae in the necks of camels and giraffes, and it’s not hard to find photos that show these. It makes sense: these are stinkin’ mammals with the usual seven cervical vertebrae, so the verts have to be longer, proportionally, and bend farther at each joint than in other long-necked animals. I’m more skeptical about the claim that individual vertebrae can be seen in the necks of large ground birds. I’ve dissected the necks of an ostrich, an emu, and a rhea, and it seems to me that the neck muscles are just too thick to allow the individual vertebrae to be picked out. In a flamingo, certainly–see the sharp bends in the cranial half of the neck in the photo below–but flamingos have freakishly skinny necks even for birds, and their cervicals are proportionally much longer, relative to their width, than those of even ostriches.
What about sauropods? As discussed in this post, sauropod cervicals were almost certainly proportionally closer to the surface of the neck than in birds, which would tend to make them more likely to be visible as bulges. However, the long bony rods of the cervical ribs in most sauropods would have kept the ventral profile of the neck fairly smooth. The ossified cervical ribs of sauropods ran in bundles, just like the unossified hypaxial tendons in birds (that’s Vanessa Graff dissecting the neck of Rhea americana below), and whereas the latter are free to bend sharply around the ventral prominences of each vertebra, the former were probably not.
All of which applies to sauropods with long, overlapping cervical ribs, which is most of them. But as mentioned above, diplodocoids had short cervical ribs. Presumably they had long hypaxial tendons that looked very much like the cervical ribs of sauropods but just weren’t ossified. Whether the vertebrae could have bent enough at each segment to create bulges, and whether the overlying muscles were thin enough to allow those bends to be seen, are difficult questions. No-one actually knows how much muscle there was on sauropod necks, not even within a factor of two. There has been no realistic attempt, even, to publish on this. Published works on sauropod neck muscles (Wedel and Sanders 2002, Schwarz et al. 2007) have focused on their topology, not their cross-sectional area or bulk.
But then there’s Apatosaurus (AMNH mount shown here). If any sauropod had a chance of having its cervical vertebrae visible from the outside, surely it was Apatosaurus. And in fact I am not opposed to the idea. The cervical ribs of Apatosaurus are unusual not only in being large and robust, but also in curving dorsally toward their tips. If one accepts that the cervical ribs of sauropods are ossified hypaxial tendons–which seems almost unarguable, given that the cervical ribs in both crocs and birds anchor converging V-shaped wedges of muscle–then the ossified portion of each cervical rib must point back along the direction taken by the unossified portion of the tendon. In which case, the upwardly-curving cervical ribs in Apatosaurus suggest that the muscles inserting on them were doing so at least partially from above. So maybe the most ventrolateral portion of each rib did stick out enough to make an externally visible bulge.
Maybe. Many Apatosaurus cervical ribs also have bony bumps at their ventrolateral margins–the ‘ventrolateral processes’ or VLPs illustrated by Wedel and Sander (2002: fig. 3). If these processes anchored neck muscles, as seems likely, then even the immense cervical ribs of Apatosaurus might have been jacketed in enough muscle to prevent them from showing through on the outside.
Still. It’s Apatosaurus. It’s simply a ridiculous animal–a sauropod among sauropods. If this were a model of Mamenchisaurus and it had visible bulges for the cervical rib loops, I’d be deeply skeptical. For Apatosaurus, it’s at least plausible.
Because the cervical ribs are visible in the maquette as distinct bulges, it’s possible to count the cervical vertebrae. Apatosaurus has 15 cervicals, and that seems about right for the maquette. The neck bumps reveal 11 cervicals, but they don’t run up all the way to the head. This is realistic: the most anterior cervicals anchored muscles that supported and moved the head, and these overlie the segmental muscles and cervical ribs in extant tetrapods. The most anterior part of the neck in the maquette, with no cervical rib bumps, looks about the right length to contain C1-C3. Plus the 11 vertebrae visible from their bumps, that makes 14 cervicals, and the 15th was probably buried in the anterior body wall.
One last thing: because the cervical ribs are huge, the neck of Apatosaurus was fat. To the point that the head looks almost comically tiny, even though it’s about the right size for a sauropod head. I first got a visceral appreciation for this when I was making my own skeletal reconstruction of Apatosaurus, for a project that eventually evaporated into limbo. Once you draw an outline of flesh around the vertebrae, the weirdness of the massive neck of Apatosaurus is thrown into stark relief. Apatosaurus is robust all over, but even on such a massive animal the neck seems anomalous. I don’t know what Apatosaurus was doing with its neck, but it’s hard not to think that it must have been doing something. Anyway, I bring this up because the maquette captures the neck-fatness very well. So much so that when I sit back from the computer and my eyes roam around the office and fall on the maquette, I can’t help thinking, for the thousandth time, “Damn, that’s weird.”
In sum, the neck of the Sideshow Apatosaurus maquette gets the non-circular cross-section right, appears to have the correct number of cervical vertebrae, and looks weirdly fat, which turns out to be just right for Apatosaurus. The bumps for the individual vertebrae are plausible, and the maquette correctly avoids the dished-in, emaciated appearance–cocaine chic for sauropods–that has become popular in recent years. It manages to be eye-catching and even mildly disturbing, even for a jaded sauropodologist like yours truly, in that it confronts me with the essential weirdness of sauropods in general, and of Apatosaurus in particular. These are all very good things.
Next time: as much of the rest of the body as I can fit into one post (all of it, it turned out).
- Paul, G.S. 1988. The brachiosaur giants of the Morrison and Tendaguru with a description of a new subgenus, Giraffatitan, and a comparison of the world’s largest dinosaurs. Hunteria 2(3):1-14.
- Paul, G.S. 2010. The Princeton Field Guide to Dinosaurs. Princeton University Press, 320 pp.
- Schwarz, D., Frey, E., and Meyer, C.A. 2007. Pneumaticity and soft−tissue reconstructions in the neck of diplodocid anddicraeosaurid sauropods. Acta Palaeontologica Polonica 52(1):167–188.
- Wedel, M.J. 2005. Postcranial skeletal pneumaticity in sauropods and its implications for mass estimates; pp. 201-228 in Wilson, J.A., and Curry-Rogers, K. (eds.), The Sauropods: Evolution and Paleobiology. University of California Press, Berkeley.
- Wedel, M.J., and Sanders, R.K. 2002. Osteological correlates of cervical musculature in Aves and Sauropoda (Dinosauria: Saurischia), with comments on the cervical ribs of Apatosaurus. PaleoBios 22(3):1-6.