November 21, 2011
- Part 1: intro
- Part 2: the head
- Part 3: the neck
- Part 5: posture
- Part 6: texture and color
- Part 7: verdict
A long-running theme here at SV-POW! is that the torsos of most sauropods were not just deep and slab-sided, they were unusually deep and slab-sided, more so than in most other tetrapods (see this and this, and for a more pessimistic take, this). This is something that is easy to get wrong; we are used to seeing round mammalian torsos and a lot of toy sauropods have nearly circular cross-sections. A lot of sculptors of collectible dinos do get the torso cross-section right, though, and the folks who made this Apatosaurus are no exception.
Next item: there’s an upward kink at the base of the tail, as there should be. Gilmore was the first to point this out, in his 1932 paper on the mounting of the Smithsonian Diplodocus (that’s plate 6 from that paper above; the skeleton on the bottom is the more correct one). This came up in the comment thread of the first post in this series, and since I haven’t had any deeper thoughts on the issue in the past week, I’m just going to copy and paste what I wrote then:
The upkink at the base of the tail is unavoidable; the sacrum is shaped like an inverted keystone and there’s no way to get the proximal caudals to do anything but angle upward without disarticulating them…. The reverse keystoning of sauropod sacra is weird. And it’s in every sauropod sacrum I can remember seeing with my own eyes, including Brachiosaurus altithorax. And yet the only authors I can think of off the top of my head who have discussed it seriously are Gilmore (1932), Greg Paul (2010, maybe a magazine article or two I haven’t seen), maybe Jim Jensen (1988), and IIRC Salgado et al. (1997). If there are more, please let me know–this is something I’m very curious about.
The back is gently arched, with the highest point about midway between the shoulder and hip joints. Where the highest point in the back falls depends on a host of factors, including the relative lengths of the forelimb and hindlimb bones, the amount of cartilage on the ends of those bones, the position and angle of the scapula on the ribcage, and the intrinsic curvature, if any, of the articulated series of dorsal vertebrae, which were themselves separated by an unknown amount of cartilage. Opinions are all over the map on most of these issues, particularly scapular orientation. As a scientist, I am agnostic on most of these points; I don’t think that they’re beyond being sorted out, but there’s a lot of work in progress right now and I haven’t seen evidence that would definitely convince me one way or another. So in lieu of saying that Apatosaurus must have had this scapular orientation and that dorsal curvature and so on, I’ll just note that the maquette has been a dominant feature in my office for a few weeks now and nothing about the body profile, shoulder position, or limb length has ever struck me as odd or worthy of comment. It looks like Apatosaurus to me. Moving on…
In the last post I talked about the visible bulges in the neck that allow one to count the cervical vertebrae. The maquette also has low bumps along the back that mark the neural spines of the dorsal vertebrae. This doesn’t strike me as unreasonable. Attachment scars for interspinous ligaments run all the way up to the tips of the neural spines in most sauropods, so the entire height of one neural spine was often webbed to the next by a continuous ligamentous sheet, as Janensch (1929: plate 4) drew for Dicraeosaurus in the illustration above (isp.L). I don’t think those ligaments would have prevented the bony tips of the vertebrae from being visible, necessarily, and the epaxial muscles should have been on either side of the interspinous ligaments and in the triangular spaces between the spine tips and the transverse processes.
What might have smoothed out the dorsal body profile are supraspinous ligaments (ssp.L in the plate above). These are present in crocs (Frey 1988: figs. 14, 16, 17) but apparently absent in most birds; at least, I haven’t seen any myself, and the Nomina Anatomica Avium does not mention any (Baumel et al. 1993: 156-157). So on phylogenetic grounds their presence in sauropods is equivocal. That said, the tips of the neural spines in most sauropods are fairly rugose. Does that mean that they were webbed one to the next by interspinous ligaments only, or that they were embedded in supraspinous ligaments as well? I don’t know the answer, and I don’t know if anyone else does, either. The whole issue of intervertebral ligaments in sauropods has received too little attention to date. In the absence of better data, I’ll just say that although I wouldn’t put any money on the proposition that the spines made externally visible bumps in life, neither does it offend me.
There is one fairly nit-picky point that I am honor-bound to mention. Because the dorsal neural spines make bumps, it is possible to count the dorsals, just like the cervicals last time. And this count doesn’t work out quite as well. Apatosaurus should have 10 dorsal vertebrae, but try as I might I can’t see more than 8 bumps along the back, and that’s generously assuming that c14′s spine is pretty well ahead of its rib. Is this pathologically anal to complain about? Quite possibly. On the other hand, by sculpting in those details the artists were basically begging geeks like me to come along and count vertebrae just because we could.
The tail is pretty cool. It is appropriately massive where it leaves the body, and has a visible bulge for the caudofemoralis muscle, which originated in the tail and inserted on the fourth trochanter of the femur. The caudofemoralis is the major femur retractor in lizards and crocs and in most non-avian dinosaurs, and rather than go on about it I’ll just point you to Heinrich Mallison’s awesome post about dinosaur butts. The tail of the maquette also has an awesome whiplash. I could say a ton more about the hypothesized uses of whiplash tails in diplodocids and other sauropods, but I don’t feel like climbing that hill just now. Suffice it to say that the maquette’s whiplash is pretty sweet, and avoids the “scale is too small so I just stuck in a piece of wire” mode of making whiplashes that I’ve seen in other, smaller diplodocid sculpts.
The tail has a row of little spines running down the dorsal midline, which have been de rigeur for life restorations of diplodocids and many other sauropods (ahem) since they were first reported by Czerkas (1993). AFAIK, such spines have only been found preserved in the tail region of diplodocids. That’s not to say that they weren’t present in the neck or the back of diplodocids, or in other sauropod taxa, just that the only good fossil traces of them to date have been from the tails of diplodocids, and maybe just one or two tails. So the presence of little spines in the tail of the maquette and not the back or the neck is perfectly–one might even say slavishly–consistent with the fossil evidence. I’ll discuss the flamboyancy or lack thereof in the maquette in another post, so I’ll say no more about this design choice for now.
The limbs are mostly good. The muscles under the skin look plausible, with one exception. As noted before in this series, Apatosaurus was a freakishly robust critter, and the limbs look appropriately sturdy and well-muscled, except where the thigh meets the hip. There is a visible bulge for the ilium, and the anterior margin of the thigh should converge with the most forward point on the ilium. That’s what the preacetabular blade of the ilium is for: to anchor thigh muscles (discussed here, and also nicely illustrated here). Unless the animal had some kind of wasting disease, there was no bone sticking out beyond the muscle, and so the anterior-most point of the ilium has to be the start of the anterior margin of the thigh.
On the positive side, there’s a little ridge running down from the anterior arm onto the forearm for the biceps tendon, which is a nice touch. The manus shows the short, solid arc of metacarpals typical for diplodocids, and an inward-curving thumb claw. The hind feet have the big laterally-curving claws on the first three digits that one expects.
In a way that is difficult to describe in words, the feet really look they are bearing a lot of weight, and this impression of solidity helps to ground the whole maquette. It doesn’t look like a sauropod-shaped balloon that just happens to be poling itself along with limbs that barely touch the ground–an impression that I have gotten occasionally from some other sculptures with overly skinny limbs and too-small feet. This critter looks big, heavy, and powerful, and those are exactly the adjectives one wants to come to mind when looking at Apatosaurus. (I do wonder if doing a Diplodocus in the same scale would be more difficult. How do you convey ‘multi-ton animal’ and ‘gracile’ at the same time?)
To sum up, in the trunk, tail, and limbs I find much to like and little to criticize. The only noteworthy problems are the insufficient dorsal count and the mismatch between the ilium and anterior thigh profile. On one hand these are puzzling goofs, given the overall attention to detail and the numerous points at which the sculpt is not just good but surprisingly good. On the other hand, I didn’t notice the dorsal thing until I bothered to count, and I didn’t notice the thigh thing until the other day when I was writing the first draft of this post, so both problems went unnoticed for weeks and are probably below the threshold of perception for the vast majority of people. The accuracy of the sculpt is so high that my approach to its problems has not been, “Where do I begin?” but rather, “What is keeping this thing from being perfect?” And the answer is, not very much.
The base is nice. It’s not just a generic slab of earth, it’s a muddy surface marked with the tracks of other dinosaurs, including a couple of theropods. The base sits nice and flat, and the Apatosaurus sits nice and flat on it, with no rocking at either point of contact. Not only do the feet of the Apatosaurus fit neatly into the sculpted footprints, one of the hindfeet has a little metal rod that slots into a socket in one of the hindfoot prints, to keep the maquette firmly on the base. That means that if you want to display the maquette off the base, you’ll have to either cut off the rod or make sure that your alternative surface will accommodate it.
The skull is…less satisfying. It’s a nice enough rendition of an Apatosaurus skull, and if it had come by itself I would have been very happy with it. The trouble is that the maquette is considerably more detailed, so when the skull sits next to the maquette it suffers by comparison. But what else are you going to do with it? Make a separate shrine to Apatosaurus somewhere else?
The difference in sculpt quality between the maquette and base on one hand and the skull on the other is apparent even on casual inspection. My copies are sitting on a bookcase adjacent to my office door. Sometimes people walking down the hall pop their heads in, and so far the most common comments are that the maquette is “awesome” and that the base is “cool”. People have been genuinely impressed that the base is a realistically detailed chunk of the environment and not just a flat slab. The only people who have commented on the skull have said that it seems “lame” compared to the maquette.
The base is included in the basic package with the maquette, in a limited edition of 500, which as of this writing goes for $289.99 (here). The package with the skull accessory is in an edition of 100, and goes for $299.99 (here). So the skull is only $10 more, and although it is not quite as nice as the maquette, I think it’s a steal at the price. Mine is certainly not going anywhere.
So much for the gross anatomy. You probably noticed that I haven’t said anything about how the maquette is posed or textured or colored. Those will all be topics for next time.
- Baumel, J.J., King, A.S., Breazile, J.E., Evans, H.E., and Vanden Berge, J.C. (eds.) 1993. Handbook of Avian Anatomy: Nomina Anatomica Avium, 2nd ed. Publications of the Nuttall Ornithological Club, No. 23. Cambridge, Massachusetts, 779 pp.
- Czerkas, S.A. 1993. Discovery of dermal spines reveals a new look for sauropod dinosaurs. Geology 20:1068–1070.
- Frey, E. 1988. Anatomie des Körperstammes von Alligator mississippiensis Daudin.
- Gilmore, C. W. 1932. On a newly mounted skeleton of Diplodocus in the United States National Museum. Proceedings of the United States National Museum 81:1-21.
- Janensch, W. 1929. Die Wirbelsäule der Gattung Dicraeosaurus. Palaeontographica Suppl. 7(1), 3(2), 37-133.
- Jensen, J.A. 1988. A fourth new sauropod dinosaur from the Upper Jurassic of the Colorado Plateau and sauropod bipedalism. Great Basin Naturalist 48(2):121-145.
- Paul, G.S. 2010. The Princeton Field Guide to Dinosaurs. Princeton University Press, 320 pp.
- Salgado, L., R.A. Coria, and J.O. Calvo. 1997. Evolution of titanosaurid sauropods. I: Phylogenetic analysis based on the postcranial evidence. Ameghiniana 34:3-32.
November 16, 2011
This is the second in a series of posts in which I review the Sideshow Collectibles Apatosaurus maquette. The rest of the series:
- Part 1: introduction
- Part 3: the neck
- Part 4: body, tail, limbs, base, and skull
- Part 5: posture
- Part 6: texture and color
- Part 7: verdict
First, a note on the photos. There a few minute white flecks on the head in the pictures. These are near-microscopic pieces of styrofoam packing material, which I only discovered after I’d shot the photos–they are, seriously, too small to be noticed otherwise. Just be aware that they are not flaws in the paint. The whole head, from external ear to snout tip, is 35 mm long, which gives you some idea of the quality of the sculpting and painting. The entire maquette is detailed to the same degree.
The general form and proportions are a good match for the skull of Apatosaurus. In particular, the head is roughly rectangular in dorsal view, with a very squared-off snout. Among extant animals, square snouts are typically found among grazers, and grazing on low-growing vegetation has been suggested for diplodocids as well (Stevens and Parrish 1999, Whitlock 2011). It is worth keeping mind, however, that anatomy is not destiny (Smith and Redford 1990); the behavior of living animals is often more varied than their skeletal form might suggest, and in some cases morphological specialization can lead to ecological generalization.
In a paper with direct relevance to grazing and browsing, Feranec (2003: 230) analyzed the diet of the Pleistocene camel Hemiauchenia. He found that “hypsodonty is not strictly associated with obligate grazing; instead it may, in this case, represent an adaptation to widen niche breadth that allowed grazing as well as browsing.” In other words, the tall, long-wearing (hypsodont) teeth necessary for eating tough grass do not prevent hypsodont herbivores from browsing on softer vegetation as well, whereas committed browsers with lower tooth crowns would have a harder time dealing with tough, abrasive grasses.
Sauropods didn’t chew their food, so tall grinding molars are beside the point, but snout shape is not. It is possible that a broad snout widened the niche breadth of diplodocids to allow both grazing and browsing, whereas a narrow-snouted sauropod like Camarasaurus would probably have made a poor grazer. I’m not discounting the hypothesis that diplodocids were partially or even predominantly grazing animals–in particular, it would help make sense of Nigersaurus, which seems to have taken the grazing adaptations seen in other diplodocoids to an extreme. Just pointing out that certain kinds of morphological specializations broaden, rather than narrow, the ecological opportunities of the animals that bear them. I should also point out that Whitlock’s (2011) analysis did not rely on muzzle shape alone but also on some interesting tooth microwear data. That paper is well worth reading, and happily it’s free, so go read it if you haven’t.
Back to the maquette. Several issues of the soft tissues of the head deserve comment.
The nostrils are down near the end of the snout, as predicted by Witmer’s (2001) work on nostril position in extant vertebrates. I know that some people are skeptical about the nostril position in dinosaurs hypothesized by Witmer, but it makes good sense to me. First, in formulating the hypothesis, Witmer did something that none of his critics have done, which is actually establish the nostril position in a wide range of extant animals. By itself, this doesn’t show what the nostril position in dinosaurs must have been, but it establishes a null hypothesis, which should only be discarded if there is compelling evidence to the contrary. And the scarcity of counterexamples among extant vertebrates constitutes a second, normative argument: if the default nostril position was an easy constraint to break, we’d expect to see more taxa that have broken it. (Both of these arguments also apply to the alert neck posture of tetrapods, by the way.)
Second, Witmer’s hypothesis has explanatory power: it makes sense of the troughs and tracks in front of the nostrils in sauropods with retracted nares. These tracks are most clearly expressed in the skull of Giraffatitan (see, e.g., the images at the top of this post), but they are present in other sauropods as well, like the Denver museum Brachiosaurus sp. skull shown above. Witmer’s hypothesis of nostril position made good sense to me because of my experience working on postcranial pneumaticity in sauropods. External pneumatic traces on sauropod vertebrae often consist of pneumatic foramina set inside larger pneumatic fossae (see, for example, this, from here). Similarly, the bony nares of sauropods can be thought of as pneumatic foramina set at the posterior end of the pneumatic fossae formed by the troughs and tracks on the snouts.
One last thing on nostril position in dinosaurs. I’ve seen people argue that terminal nostrils would have been bad for dinosaurs (especially carnivores) because they would have gotten poked by vegetation or fouled with food. To which I can only say, good people, stop trying to figure out dinosaurs from first principles and just look at live animals.
Next item: the teeth are covered by fleshy lips. The hypothesis that some dinosaurs had lips is not new, but it hadn’t received much technical attention until recently. Enter Ashley Morhardt (research page, blog). For her MS work under Matt Bonnan (research page, blog) at Western Illinois University, she did something that no one had done before: she counted nutrient foramina (blood vessel holes) in the jawbones of extant vertebrates and related foramina counts to the kinds of soft tissues the jaws supported: marginal scales, muscular lips, beaks, and so on. Then she looked at dinosaurs and applied what she’d learned. That work is still on the road to publication, so I won’t give away the game. But I did ask Ashley specifically about the plausibility of the lips in the Apatosaurus maquette, and she was kind enough to share her thoughts. She writes (with permission to cite):
The foramina present at the margin of Apatosaurus‘ mouth are more similar in relative size, shape, and distribution to those of crocodylians than those of mammals. … A conservative EPB approach would shy away from reconstruction that might include any type of fleshy seal at the oral margin. This would leave the teeth bare and the posterior margin of the mouth covered in skin without any overhanging scales. … The current maquette is gorgeous, but potentially incorrect.
Ashley is now working on her PhD with Larry Witmer (research page, blog) at the University of Ohio, and we can surely expect more cool science from her in the future. Please also note that the question of dinosaur lips was recently the subject of a long, thoughtful post by Jaime Headden.
Since this post involves soft tissues of sauropod heads, I’m contractually obligated to point out that, like the maquette, real sauropods didn’t have trunks.
Finally, I’m happy to say that the head avoids shrink-wrapped dinosaur syndrome. There’s enough underlying anatomy to show that It’s built up from the skull of Apatosaurus, but you can’t see every little ridge and divot in the skull (nor should you). And the soft tissues are plausible and detailed, so the head doesn’t just look like a smooth bullet of meat. And the sculpting itself is detailed enough to support close examination. All of these are big pluses, even if the lips are a (small) step beyond what our current understanding will support.
- Feranec, R.S. 2003. Stable isotopes, hypsodonty, and the paleodiet of Hemiauchenia (Mammalia: Camelidae): a morphological specialization creating ecological generalization. Paleobiology 29(2):230-242.
- Smith, K.K., and Redford, K.H. 1990. The anatomy and function of the feeding apparatus in two armadillos (Dasypoda): anatomy is not destiny. Journal of Zoology 222:27-47.
- Stevens, K.A. and Parrish, J.M. 1999. Neck posture and feeding habits of two Jurassic sauropod dinosaurs. Science 284: 798-800.
- Whitlock, J.A. 2011. Inferences of diplodocoid (Sauropoda: Dinosauria) feeding behavior from snout shape and microwear analyses. PLoS ONE 6(4):e18304. doi:10.1371/journal.pone.0018304
- Witmer, L.M. 2001. Nostril position in dinosaurs and other vertebrates and its significance for nasal function. Science 293:850-853.
November 15, 2011
I only learned about a month ago that this exists. Mike had written to Sideshow Collectibles and offered to review their Apatosaurus maquette if they’d send him a review copy. The folks at Sideshow were game, and would have sent Mike a complimentary review copy and covered the shipping. But the import fees would have been appalling, so Mike very generously suggested that they send it to me instead. And here we are.
I’m grateful for the opportunity to review the Sideshow Apatosaurus maquette, not only because it’s a nice piece of kit that looks great in my office, but also because it gives me the opportunity to discuss some aspects of sauropod anatomy and behavior that haven’t come up here at SV-POW! before. Some of these are right on the cutting edge of sauropod paleobiology, and hopefully they’ll be good fodder for discussion.
As usual, what started in my mind as a fairly brief series of comments metastasized into something ponderous, so I’m breaking up the review into a series of posts, each of which will deal with different aspects of anatomy, function, and behavior. Links to the rest of the series are at the bottom of this post.
Something that looms over any review is the problem of objectivity, especially when the reviewer has received a complimentary copy of the review item. Maybe I’m a bit paranoid about this; after all, complimentary review copies are SOP for technical reviews in many fields, including reviews of academic books. In any case, I’ve been blathering about dinosaurs in public for many years now, so anything I say in this review series can be checked against what I’ve said before on the same topics. Also, I reference a lot of published work in the upcoming posts, so you won’t have to take my word where most points are concerned. Finally, insofar as possible, I’ll try to keep my personal opinions about the Apatosaurus maquette out of the main series of posts. I’ll tell you what I personally think about it–beyond the fact that it’s “a nice piece of kit”–in the conclusion to the series.
Links to the rest of the series:
- Part 2: the head
- Part 3: the neck
- Part 4: body, tail, limbs, base, and skull
- Part 5: posture
- Part 6: texture and color
- Part 7: verdict
November 7, 2011
This is the second post on the Wedel lab’s recently acquired skull of Ursus americanus, the American black bear. The first installment covered ended with the disinterred-but-still-filthy skull bits sitting on my dining room table. This post covers putting the teeth back in, and just enough anatomy to justify putting up more cool pictures.
About five minutes after I took the last picture from the last post, I put the cranium and mandible to soak in warm, soapy water and spent the rest of the day doing other things. Last night I got a couple of old toothbrushes and scrubbed off most of the dirt from the external surfaces of the skull. I alternated toothbrush work with running water from the bathtub faucet over and through the skull bits. I also used one of the rubber nasal aspirator bulbs (or “snot suckers”, as new parents in the real world invariably call them)–which make tremendous water guns–to sluice out some of the grimier cavities. It was fun to force water into the mandibular foramen and see it come shooting out the mental foramen, along the canal traveled by the inferior alveolar nerve and vessels.
All of the teeth were loose in their sockets, and the incisors and upper canines were either falling out or could be pulled out without too much trouble. I yanked all of the teeth that I could, figuring that it was better to yank-and-glue rather than leaving them loose. I set the loose teeth on separate plates, one upper, one lower, arranged in the same order they were in the alveoli, and let everything air dry overnight.
Shown above is my setup for replacing the teeth:
- a trash bag for protecting the table
- a dish towel to provide a soft surface
- the bear skull pieces
- loose teeth on their respective plates
- five minute epoxy
- toothpicks for mixing and spreading the epoxy
I had been going to use something less hardcore for the gluing, but fortunately Vicki got home and I was able to draw on her experience from reconstructing loads of human skulls from archaeological and forensic sites. She said just go with epoxy, and so I went.
Here we are about halfway through the process. A few tips, some obvious, some maybe less so:
- Even if you’ve done a perfect job of keeping the teeth in order, test-fit them anyway. If nothing else, this will give you a visceral sense of what the tooth feels like sliding into the socket, and it will help you figure out how much glue to apply. Also, test fit adjacent teeth together so you’ll know if they have to go back in in a particular order; sometimes one tooth is at a subtle angle and blocks the next tooth from coming out or going back in.
- Better to put the glue in the socket than on the tooth. The roots are not much smaller in diameter than the alveoli and the crowns stand out a bit from the bone (although the ‘exposed’ roots would have been covered with gums in life). If you put the glue on the tooth you’re liable to either have it bulldozed off by the alveolar rim as you slide the tooth into the socket, or you’ll put too much on and have a bunch of worthless glue on the exposed portion of the root.
- If the teeth are worn, like the incisors are here, it’s nice to do a bunch at once so you can get all of the wear surfaces lined up as they were in life. Better than having one tooth set up completely and then realizing it was all the way forward/back/in/out and the other teeth can’t match its orientation.
Everything back in. There are a couple of incisors still AWOL, and a few premolars, but the dentition is still reasonably complete (remember that I am used to working on Early Cretaceous North American sauropods, so a little completeness goes a long way). I ran a thin bead of epoxy around the bases of all of the teeth that had not come out of the alveoli, to hopefully rein in any future wanderlust on their parts.
Sweet action. I wish I had something more intellectual to say here, but I really don’t.
Nasal turbinates. Holy crap, were these a pain to get clean. I didn’t get them completely clean, there’s probably enough dirt up in there to germinate something. But I asymptotically approached the point where removing more dirt would have meant damaging the turbinates, which are at least manilla-envelope-thin if not laser-printer-paper-thin.
A closeup of the infraorbital foramen on the right, which transmitted the infraorbital artery and vessels in life. The neurovascular tracks on the external surface of the bone are pretty sweet; you can see them on the left side, in context, two photos up.
In addition to closing our jaws in a hinge-like motion, we can slide them fore and aft and also from side to side. Those kinds of motions are fine when you’ve got comparatively weak jaws like ours, and we still occasionally get into trouble–jawbreakers are so named for a reason. But those non-hinge-like motions would be disastrous for something that can close its jaws with several hundred pounds of force. So most big carnivores have wide, almost cylindrical jaw joints that constrain the motion to being almost purely hinge-like. In mustelids (weasels and kin), which have the strongest bites for their sizes of any mammals, the condyle is so cylindrical and the fossa so deeply enclosing (imagine a Q sitting inside a very slightly larger C–that’s the jaw joint seen from the side) that sometimes you simply can’t get the jaws to disarticulate after death. This ain’t quite that extreme, but it’s closer to the mustelid condition than the human. Not surprising, since weasels are united with bears and seals in the clade Arctoidea.
And here’s why bears need those cylindrical jaw joints: check out the muscle attachment scars on the back of the mandible. These are for the temporalis and masseter muscles, the same muscles you can feel bulging out on the side of your head and the corners of your jaw when you bite down forcefully or grit your teeth. IIRC, the maximum bite force a human can exert is around 180 pounds, and lions can do something like 900 pounds. Not sure where Ursus americanus falls, but definitely on the please-don’t-bite-me end of the scale.
And here’s why those muscle attachment scars are so big. The zygomatic arches are only partly complete here, but you can see how wide is the space between the left arch and the braincase. All of that space–two full inches, mediolaterally–was filled with temporalis muscle that provided most of the power for jaw-closing. This is why pit bulls have such wide, flat-looking heads: they have normal-sized dog brains and huge, thick jaw muscles. See also: my hyena dissection photos.
Looking very dog-like here in anterior view. There are some butchery marks on the skull, most noticeably across the external nares here, and along the mandibles. Not sure what that’s all about, since I can’t reconcile the stated backstory–cop shoots dangerous bear, buries head in backyard–with a need to make repeated cuts across the snout and jaws. And no, they’re not shovel marks. I knew that already, and Vicki confirmed that the marks are peri-mortem (around the time of death, but impossible to confirm as pre- or post-mortem). Anyway, I’m not complaining. Despite the damage, the skull is still an awesome thing, and the cut marks add a touch of mystery. I’ll post more pictures when I get the left temporal region glued back on.
November 6, 2011
After three months as a paleontology grad student, this morning Vanessa I. Graff got to sink a shovel in the service of science. Now, it was a bear skull, deliberately buried in someone’s back yard, so technically today’s exploits fall under the heading of contemporary zooarcheology rather than paleontology, but we’ll take what we can get.
This story has a backstory. The guy on the right here is Hossein Aziz, one of my advisees among the DO students at Western. His landlady’s ex-husband is in law enforcement, and about a year and a half ago he had to shoot a bear that had become a threat to humans. He buried the head in the backyard and separated from his then wife. She found out from Hossein that one of his professors was a paleontologist and offered to donate the skull to science, if only we’d come dig it up. So we did. Involved in the excavation (right to left in the above photo) were Hossein, his girlfriend Lia, my son London, Vanessa, and yours truly.
Additional note: Hossein’s landlady is a British expatriate, and she served us proper English tea. It was the most civilized dig I have been on, which, admittedly, is sort of like being the least worthless Kardashian. Anyway, the tea was great, and we all had a good time.
My wife, Dr. Vicki Wedel, was out of town, but she lent us her archaeological toolkit, so we had nice trowels and kneepads and such. Here Hossein is pretending to advise Vanessa and London on what they should be doing, which is funny because that’s usually my job (pretending, that is).
After about half an hour of digging, we found intact vertebrate remains! And there was much rejoicing.
First out of the ground was the mandible, which is in essentially perfect shape.
Ursus americanus mandible and lower dentition, Homo goofballensis for comparison and scale.
Lia and London clearing dirt from around the cranium, which looks disturbingly hominoid from this angle.
There really aren’t any words for what’s going on here. Just bask a moment in the glory and move on.
We were going for American Gothic here, but Vanessa blew it by smiling. Standard.
Lia and Hossein marveling at what is, after all, a pretty badass critter. Even a small bear has seriously impressive teeth, which you hope to never find embedded in your flesh.
Still, it can be fun to pretend otherwise.
Here’s what we have. The occipital region is just gone. The left temporal region is more intact and has a long crack leading away across the frontals. On the right, everything from the zygomatic process of the maxilla to the occiput is just gone. So I reckon the rifle bullet went in on the left and blew out an exit wound the size of an orange on the right side of the bear’s head.
After a good rinse in the tub, all the bits are now soaking in soapy water. I’ll post more pictures when I get it all cleaned up and presentable. In the meantime, many thanks to Hossein’s landlady for the skull, the tea, and her amused tolerance at having a bunch of dirty people digging in her yard, and to Hossein, Lia, Vanessa, and London for their work. It was a pretty darned good way to start the weekend.
October 6, 2011
Vanessa Graff and I spent yesterday working in the herpetology and ornithology collections at the Natural History Museum of Los Angeles County (LACM). The herpetology collections manager, Neftali Comacho, pointed us to this skull of Alligator mississippiensis. It’s not world’s biggest gator–about which more in a second–but it’s the biggest I’ve seen in person. Normally it lives in a big rubbermaid tub in the collections area, but this Sunday it will be out on display for Reptile and Amphibian Appreciation Day (RAAD) at the LACM. RAAD will include guest talks, tours of the collections, and live animal demonstrations. If you’re in SoCal and you’re into herps–or have kids, grandkids, nephews or nieces that are into herps–it will be well worth checking out. While you’re there, don’t neglect the newly renovated Age of Dinosaurs and Age of Mammals halls, which are frankly phenomenal: spacious, well-lit, loads of actual material on display, skeletons you can walk all the way around, informative but unobtrusive signage, tasteful integration with existing architecture…I could go on. Better if you just go and see for yourself.
About that gator. First the bad news. It came to the LACM from another collection, and has no data–no locality, no date collected, nothing. The skull is also missing all of its teeth, the left retroarticular process, the back end of the braincase and the occipital condyle. I think the latter losses were probably caused by a foramen of Winchester.*
Now, the awesome news. The length from the snout tip to the end of the articulars was 680mm and from the snout to the end of the quadrates was 590mm. Irritatingly I did not get a dorsal head length, which is the gold standard for comparative croc skull measurements, because I only reread Darren’s giant croc skull post after I got home last night. Going from the photos, I think the dorsal head length was right around 50 cm (beware, the yardstick in the photos is marked off in inches).
Darren’s post led me to this one, which has some very useful measurements (yay!) of giant croc skulls. The table at the end of that post lists alligator skulls with dorsal head lengths of 58, 60, and 64 cm, so the big LACM gator is nowhere near being the world’s largest. In fact, the 64 cm skull would be a quarter again as large, which is a truly horrifying thought. Still, it’s a big damn skull from a big damn gator.
You might get the impression that here in the Wedel lab we are shamelessly obsessed with giant saurians. And that is in fact true. But we also look at tiny ones, too. Here I’m playing with the skull of a little Tomistoma, the false gharial. Tomistoma is notable because another individual of the genus produced the longest skull of any known extant crocodilian–a whopping 84 cm dorsal head length (photos of this monster are in both of the giant croc skull posts linked above).
The moral of the story? If the sign says don’t go swimming, don’t go swimming. Go to RAAD instead, and see the giant alligator skull, and a ton of other cool stuff besides. And if you’re into gator skulls or just like geeking out on awesome anatomy, check out the 3D Alligator Skull site, a joint project of the Holliday lab and Witmer lab. Have fun!
* bullet hole
September 1, 2011
In a recent post I showed photos of the trachea in a rhea, running not along the ventral surface of the neck but along the right side. I promised to show that this is not uncommon, that the trachea and esophagus of birds are usually free to slide around under the skin and are not constrained to like along the ventral midline of the neck, as they usually are in mammals. Here goes.
Here’s figure 5 from van der Leeuw et al. (2001): a lateral x-ray of a duck, reaching up just a bit with its head and neck, possibly to get a bite or just look around. Click through for the unlabeled version.
There’s a LOT of stuff going on in this image:
- As promised, the trachea (blue lines) is taking a very different path to the head than the vertebrae and skeletal muscles.
- As usual for tetrapods, the neck is extended
at the basein the caudal half and flexed at the headin the cranial half.
- The epaxial (dorsal) muscles at the base of the neck are not tied down to the vertebral column so they are free to bowstring across the U-bend at the base of the neck (black arrow)–this was the point of the figure in the original paper. Although the gross outline of the neck also deviates from the vertebral column on the ventral side near the head, this is caused by the trachea and gullet approaching the pharynx, not because the hypaxial muscles are bowstringed across the curve.
- As the post title intimates, this neck lies: the cervical vertebrae are significantly more extended than one would expect based on the external appearance of the neck alone. The red line shows the angle of the most strongly retroverted vertebra, which I measure at 48.5 degrees from vertical (41.5 degrees above horizontal)–slightly closer to horizontal than to vertical! We have seen this before, in most mammals and in a couple of small birds (see this post); here we see it even in a reasonably large, long-necked bird.
- Worse, the gross outline of the neck–what one can see from the outside–lines up with nothing on the inside: the trachea is less curved and the vertebral column is more curved.
Same points again, this time in a chicken in an alert posture (Vidal et al. 1986: fig. 7). Here the most strongly retroverted cervical is 36 degrees from vertical (54 degrees above horizontal).
What’s all this got to do with sauropods?
First, it shows that even in animals with long, slender necks, it’s not enough to show a photo or painting of an extant animal and make assertions about what the cervicals are doing (necks lie, again). It’s even less defensible to make the dual assertions that (a) the gross outline of the neck shows the path of the cervicals and (b) the cervicals are in ONP, all based on a photo or painting of a living animal. The first point can only be established by radiography, and the second by manipulation of the skeleton, either physically or digitally. It may seem like I’m tilting at windmills here, but we’ve seen these very assertions made in conference talks. As always, we’ll follow where the evidence leads, but not until we see some actual evidence.
Second, I am increasingly haunted by the idea that we are all waaay too influenced, even (maybe especially) subconsciously, by big mammals when we think about sauropods and their necks. Big mammals–like, say, horses and giraffes–have:
- only 7 cervical vertebrae;
- lots of big muscles that attach to the thorax and the head and cross the cervical column without attaching to it much or at all;
- presacral neural spines that max out, height-wise, over the shoulders, creating withers;
- alert neck postures that are elevated (like all tetrapods) but often short of vertical, with the vertebrae often held more-or-less straight through the middle section of the neck (camels are an obvious exception here).
In contrast, birds have:
- many cervical vertebrae, from a 12 or so up to 27 or 28;
- almost no muscles that span from thorax to skull;
- presacral neural spines that rise monotonically to the synsacrum (except–maybe–in Giraffatitan);
- alert neck postures that are S-shaped, with the craniocervical joint over or just slightly in front of the cervicodorsal junction.
Which group sauropods had more in common with is left as an exercise for the reader.
- van der Leeuw, A.H.J., Bout, R.G., and Zweers, G.A. 2001. Evolutionary morphology of the neck system in ratites, fowl, and waterfowl. Netherlands Journal of Zoology 51(2):243-262.
- Vidal, P.P., Graf, W., and Berthoz, A. 1986. The orientation of the cervical vertebral column in unrestrained awake animals. Experimental Brain Research 61: 549-559.
August 21, 2011
Something about this photo from the last post has been bugging me all week. It’s the expression on my face. The set jaw, the thrust forward chin, the cocked eyebrow…I knew I had seen these things before. It took me a while, but I was finally able to place it. My doppelganger:
If this is an omen, I have no idea what it means.
Science will resume shortly.
June 9, 2011
Every now and then, you come across a sauropod skull so beautiful, it’s almost enough to distract you from the vertebrae that it was attached to. One such is the Giraffatitan brancai skull HMN T1, which you’ve seen here before if you’ve been around for a while.
(I am not kissing the real thing, but a slightly scaled 3d print of a scan made from the original.)
This is one of the many photos from the Berlin visit that was part of the German sauropod working group‘s 2008 conference. That conference, the first they held that was open to people outside of their group, was the best one I have ever been to. This year, they are holding a second conference, and Matt and I plan to be there again. It’ll be in early December; no doubt we’ll report back when we return.
April 7, 2011
“Sauropods are basically alien animals . . . What can be said of the habits of an animal with the nose of a Macrauchenia, the neck of a giraffe, the limbs of an elephant, the feet of a chalicothere, the lungs of a bird, and the tail of a lizard? With so many plausible but conflicting interpretations, it is unlikely there will be general agreement on sauropod habits as long as more than one paleontologist has an opinion on the matter.”
–Walter Coombs, 1975, “Sauropod habits and habitats”, page 29
I first encountered that passage at age 9, in The Dinosaurs, by William Stout, William Service, and Bryon Preiss. Peter Dodson quoted it in his introduction to the book, and it really stuck in my head. So much so that I quoted it myself when the opportunity arose, and now present it here for your consideration. More recent investigations have pretty well done in the idea that sauropods had trunks (for more about that, go here [which will lead you to this, which I had completely forgotten that I wrote, but quite like now that I've rediscovered it]), but the rest of Coombs’s comparisons are still apt. I had no idea when I was 9 how long a shadow the “lungs of a bird” part would cast over my life! And certainly there are aspects of sauropod biology that are still contentious, and some may always be so.
But I really feel like a synthetic view of sauropod paleobiology is emerging, and the best evidence of it to date is the massive paper by Sander et al. (2010) in Biological Reviews. That paper is one of the zillion things I’ve been intending to blog about, but have not gotten around to yet (and there’s a book by most or all of the same folks due shortly from Indiana University Press). When I read it right after it came out, I had the very strong feeling that it was a watershed moment for sauropod paleobiology, such that it will be fair to ask of any future study, “How is this an advance beyond Sander et al. (2010)?” I like papers like that–Coombs (1975) was one such–because they inspire me to start figuring out what’s going to come next.
- Coombs, W. P. 1975. Sauropod habits and habitats. Palaeogeography, Palaeoclimatology, Palaeoecology 17:1-33.
- Sander, P. M., A. Christian, M. Clauss, R. Fechner, C. T. Gee, E.-M. Griebeler, H.-C. Gunga, J. Hummel, H. Mallison, S. F. Perry, H. Preuschoft, O. W. M. Rauhut, K. Remes, T. Tütken, O. Wings, and U. Witzel. 2010. Biology of the sauropod dinosaurs: the evolution of gigantism. Biological Reviews. doi: 10.1111/j.1469-185X.2010.00137.x.