This past weekend I was camping up the coast at Hearst San Simeon State Park, with my son, London, and Brian Engh.

We went to see the elephant seal colony at Piedras Blancas. It was my first time seeing elephant seals in the wild. Not having done any research in advance, I was expecting something like this:

In other words, a small number of elephant seals, not doing much, basically at binocular distance from the viewing area. Obviously we did get some of that, since I have a picture of it. But that was up the coast a bit, at the start of Boucher Trail near the Piedras Blancas lighthouse.

We spent most of our time at the main Piedras Blancas rookery, where just the southeastern half of the viewing area looked – and sounded – like this:

We also saw a lot of this (semi-groady iPhone-through-binocular shot by me):

and even some of this (much nicer photo courtesy of Brian Engh):

I’ll have a lot more to say about this real soon, including more video, but it’s late and I need sleep. Stay tuned!

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This post started out as a comment on this thread, kicked off by Dale McInnes, in which Mike Habib got into a discussion with Mike Taylor about the max size of sauropods. Stand by for some arm-waving. All the photos of outdoor models were taken at Dino-Park Münchehagen back in late 2008.

I think it’s all too easy to confuse how big things do get from how big they could get, assuming different selection pressures and ecological opportunities. I’m sure someone could write a very compelling paper about how elephants are as big as they could possibly be, or Komodo dragons, if we didn’t have indricotheres and Megalania to show that the upper limit is elsewhere. This is basically what Economos (1981) did for indricotheres, either forgetting about sauropods or assuming they were all aquatic.

Truly, a mammal of excellence and distinction. With Mike and some dumb rhino for scale.

In fact, I’ll go further: a lot of pop discussions of sauropod size assume that sauropods got big because of external factors (oxygen levels, etc.) but were ultimately limited by internal factors, like bone and cartilage strength or cardiovascular issues. I think the opposite is more likely: sauropods got big because of a happy, never-repeated confluence of internal factors (the Sander/et al. [2008, 2011, 2013] hypothesis, which I think is extremely robust), and their size was limited by external, ecological factors.

Take a full-size Argentinosaurus or Bruhathkayosaurus – even modest estimates put them at around 10x the mass of the largest contemporary predators. Full-grown adults were probably truly predator-immune, barring disease or senescence. So any resources devoted to pushing the size disparity higher, instead of invested in making more eggs, would basically be wasted.

If there was reproductive competition among the super-giants, could the 100-tonners have been out-reproduced by the 70-tonners, which put those extra 30 tonnes into making babies? Or would the 100-tonners make so many more eggs than the 70-tonners (over some span of years) that they’d still come out on top? I admit, I don’t know enough reproductive biology to answer that. (If you do, speak up in the comments!) But if – if – 70-tonners could out-reproduce 100-tonners, that by itself might have been enough to put a cap on the size of the largest sauropods.

Another possibility is that max-size adult sauropods were neither common nor the target of selection. In most populations most of the time, the largest individuals might have been reproductively active but skeletally-immature and still-growing subadults (keep in mind that category would encompass most mounted sauropod skeletons, including the mounted brachiosaurs in Chicago and Berlin). If such individuals were the primary targets of selection, and they were selected for a balance of reproductive output and growth, then the few max-size adults might represent the relatively rare instances in which the developmental program “overshot” the selection target.

Dave Hone and Andy Farke and I mentioned this briefly in our 2016 paper, and it’s come up here on the blog several times before, but I still have a hard time wrapping my head around what that would mean. Maybe the max-size adults don’t represent the selective optimum, but rather beneficial traits carried to extreme ends by runaway development. It seems at least conceivable that the bodies of such animals might have been heavily loaded with morphological excrescences – like 15- to 17-meter necks – that were well past the selective optimum. As long as those features weren’t inherently fatal, they could possibly have been pretty darned inefficient, riding around on big predator-immune platforms that could walk for hundreds of kilometers and survive on garbage.

What does that swerve into weird-but-by-now-well-trod ground have to do with the limits on sauropod size? This: if max-size adults were not heavy selection targets, either because the focus of selection was on younger, reproductively-active subadults, or because they’d gotten so big that the only selection pressure that could really affect them was a continent-wide famine – or both – then they might not have gotten as big as they could have (i.e., never hit any internally-imposed, anatomical or biomechanical limits) because nothing external was pushing them to get any bigger than they already were.

Or maybe that’s just a big pile of arm-wavy BS. Let’s try tearing it down, and find out. The comment thread is open.

References

Vicki and London and I were in downtown Los Angeles for a friend’s wedding on Dec. 30, and afterward we visited The Last Bookstore. Embarrassingly, even though I’m LA-adjacent, I had not been before. I believe the mounted woolly mammoth visible in the far corner was one of the last ones to be shot in the LA Basin.

The Last Bookstore is an awesome place, with two floors of new and used books, records, comics, and related esoterica. Made me nostalgic for Logos in downtown Santa Cruz, which sadly closed shop this past summer.

The visit was a momentous occasion for me. Although my book with Mark Hallett has been out for almost a year and a half now, and many copies have passed through my hands at book signings, I’d never run into one out in the wild.

I quickly and quietly did a guerilla signing, and left the book on the shelf. And I intend to keep doing them, as often as I run into unsigned copies. As a public service message, if you ever find a copy of the book out in the world that looks like it’s been signed by me, it’s probably legit (send me a pic or post in the comments if you have doubts). Since I’m inflicting these on an unsuspecting public, if you get stuck with a signed copy but would prefer otherwise, let me know and I’ll swap a fresh book for your vandalized one.

I also did okay finding books for myself. I got two: On a Piece of Chalk, by Thomas Henry Huxley, and The Anatomy of the Salamander, by Eric T.B. Francis.

On a Piece of Chalk is a legendary bit of natural history. In 1868, T.H. Huxley gave a public lecture with that title to the working folk of Norwich, during a meeting of the British Association for the Advancement of Science. A piece of chalk was both his physical tool and his subject, which he used to illustrate, literally and figuratively, the evidence for uniformitarian stratigraphy and biological evolution. Huxley’s talk has been printed twice: later in 1868 by Macmillan’s Magazine of London, and in a nice hardback in 1967 by Charles Scribner’s Sons of New York. I found a copy of the latter for five bucks, which I note is the going rate for used copies on Amazon. But I can’t actually find any evidence that my copy has been used. It appears to be utterly pristine, and I suspect it may be New Old Stock.

If you don’t own a copy of this wonderful book, you should drop what you’re doing, acquire one, and read it. If you’re reading this blog, you probably know Huxley’s punchline. But the way Huxley draws the reader in, illustrates his points with clear and compelling examples, and builds his argument steadily outward, from a piece of chalk to the vertiginous spectacle of deep time, is masterful in both concept and execution.

I know less about the salamander anatomy book, but I snagged it anyway. It’s a reprint of an original 1934 text, published in 2002 by the Society for the Study of Amphibians and Reptiles. Reproduction quality is excellent, especially of the numerous and minutely detailed plates. I picked up the book for two reasons: one, because I’m getting progressively more interested in the peripheral nervous systems of nonhuman tetrapods, and two, because I have a peculiar fetish for good illustrations of the recurrent largyneal nerve, especially in short-necked animals (for example). I did not come away disappointed.

The moral of the story? Stay alert for good natural history writing. I find that older natural history books turn up in used bookstores pretty regularly, and it’s possible to grow your library inexpensively if you are patient. And support your local bookstore, while it’s still there to support.

I have used this photo in loads of talks, but as far as I can tell, this is the first time I’ve put it up on SV-POW! (I am certain that, having said that, someone will find a previous instance – if so, consider this an extremely inefficient and lazy form of search.) The vert is OMNH 1670, the most complete and nicest dorsal of the giant Oklahoma apatosaurine, probably a D5 or D6. That’s me back in 2004. Photo by my then fellow grad student in the Padian lab, Andrew Lee. I’m 6’2″ and have normally-proportioned human arms, but if you’re trying to figure out the scale, that vert is 135cm tall, with an anterior centrum face 38cm tall by 46cm wide (partly reconstructed but probably accurate). See this post for more details and a fairly exhaustive list of measurements.

Here’s a stupid thing: roughly 2-3 times a year I go to the field or to a museum and get hundreds of SV-POW!-able photos. Then I get back to the world and catch up on all of the work that piled up while I was away. And by the time I’m done with that, whatever motivating spark I had – to get some of those photos posted and talk about the exciting things I figured out – has dissipated.

Case in point – this bitchin’ shark, prepped in ventral view, which I saw last month in the natural history museum in Vienna. Look at that fat, muscular tail – this shark is swole.

That’s dumb. And this blog is in danger of slipping into senescence, and irrelevance.

So here’s my New Year blog resolution for 2018: I’m getting us back to our roots. I, or we – I am taking this plunge without consulting with Mike (surprise, buddy!) – will post a new, never-posted-before photo, at least once a week, for the whole year. It may not always be a sauropod vertebra, but if often will be, because that’s what I have the most of, and the most to yap about. And I will try to write something interesting about each photo, without lapsing into the logorrhea that has too often made this blog too exhausting to contemplate (at least from this side of the keyboard).

Wish me luck!

Here’s my face.

I went to the dentists’ office recently for a regular checkup and cleaning, and when my dentist learned that I taught human anatomy, he volunteered to send me a high-res copy of my panoramic x-ray. I couldn’t think of any plausible scenario wherein someone could use it for evil, and it has lots of cool stuff in it besides teeth, so decided to post it so I could yakk about it.

First things first: my teeth are in pretty good shape. I had to have my wisdom teeth (3rd molars) pulled back in 2009, and my upper 1st molar on the left has a root canal and a porcelain crown, which stands out bright white on the radiograph. Everyone else is present and looking good. If it’s been a while since you’ve covered this, the full human dentition consists of 2 incisors, 1 canine, 2 premolars, and 3 molars on each side, top and bottom, for a total of 32 teeth. Because I’ve had all four 3rd molars removed, I’m down to 28.

I could go on and on about the cool stuff in this image. Here are 12 things that stand out:

  1. The mandibular condyle, which is the articular end of the mandible that fits into the mandibular fossa, a shallow socket on the inferior surface of the temporal bone, to form the temporomandibular joint (TMJ). There’s an articular disk made of fibrocartilage inside the joint, which separates it into two fluid-filled spaces, one against the condyle and one against the fossa. This allows us to do all kinds of wacky stuff with our lower jaws besides simply opening and closing them, such as slide the jaw fore and aft or side to side. This is a strong contrast to most carnivores, which bite down hard and therefore need a jaw joint that works as a pure hinge. See this post for pictures and discussion of the jaw joint in a bear skull.
  2. The coronoid process of the mandible, which is a muscle attachment site. A few fibers of the masseter and buccinator muscles can encroach onto the coronoid process, but mostly it is buried in the temporalis, one of the primary jaw-closing muscles. Put your fingers on the side of your head a little above and in front of your ear and bite down. That muscle you feel bulging outward is the temporalis. Back in the 1960s, Melvin Moss (1968) discovered that if he removed the temporalis muscles from newborn rats, the coronoid processes would fail to develop. Moss’s ambition was to discover the quanta of anatomy, which in his view were “functional matrices” – finite sets of soft tissues related by development and function, which might contain “skeletal units” that grew because of the morphogenetic demands of the functional matrices. His tagline was, “Functional matrices evolve, skeletal units respond”. Not all of Moss’s ideas have aged well in light of what we now know about the genetic underpinnings of skeletal development, but he wasn’t completely wrong, either, and functional matrix theory is still an interesting and frequently productive way to think about the interrelationships of bones and soft tissues. For more horrifying/enlightening Moss experiments on baby rats, see this post.
  3. The mandibular angle, which is another muscle attachment. The medial pterygoid muscle attaches to the medial surface, and the masseter attaches laterally. You can feel this, too, by putting your fingers over your mandibular angle and biting down – that’s the masseter you feel bulging outward. Note that the angle flares downward and outward on either side of my jaw. This flaring of the angle tends to be more pronounced in males than in females, and it is one of many features that forensic anthropologists (like the one I belong to) take into account when attempting to determine biological sex from human skeletal remains. Like most sexually dimorphic features of the skeleton, this is a tendency along a spectrum of variation rather than a binary yes/no thing. There are women with flared jaw angles (Courtney Thorne-Smith, probably) and men with slender mandibles, so you wouldn’t want to sex a skeleton by that feature alone.
  4. The mandibular canal, a tubular channel through the mandible that houses the inferior alveolar artery, vein, and nerve. This neurovascular bundle provides innervation and blood supply to the tooth-bearing part of the mandible and to the teeth themselves, and emerges through the mental foramen to provide sensory innervation and blood supply to the chin.
  5. The upper surface of the hard palate, formed by the palatine process of the maxilla anteriorly and by the palatine bones posteriorly. The palate is the roof of the mouth and the floor of the nasal airways.
  6. The median septum of the nasal cavity, formed by cartilage anteriorly, the perpendicular plate of the ethmoid bone superiorly, and the vomer posteriorly and inferiorly.
  7. The blue lines are the inferior margins of my maxillary sinuses – air-filled spaces created when pneumatic diverticula of the nasal cavity hollow out the maxillae. You have these, too, as well as air spaces in your frontal, ethmoid, sphenoid, and temporal bones. It looks like many of the roots of my upper molars stick up into my maxillary sinuses. This is not an illusion, as shown below.
  8. When I had the root canal on my left upper 2nd molar, the endodontist filled the pulp cavities of the tooth roots with gutta-percha, a rigid natural latex made from the sap of the tree Palaquium gutta. Gutta-percha is bioinert, so it makes a good filling material (it was also used to insulate transoceanic telegraph cables), and it’s radiopaque, which allows endodontists to confirm that the cavities have been filled completely. The other teeth show the typical structure of a dense enamel crown, less dense dentine forming the bulk of the tooth, and radiolucent pulp cavities containing blood vessels and nerves.
  9. This is the rubber bit I gripped with my incisors to keep my teeth apart and my head motionless while the CT machine rotated around me to make the scan. Not that cool in a science sense, but I figured it deserved a label.
  10. Note that the roots of the canines go farther into the jaws than those of the other teeth. This is true for all four canines, it’s just easiest to see with this one. This is a pretty standard mammalian thing, for taxa that still have canines – they tend to be big and mechanically important, so they have deep roots. Even though our canines are absolutely and proportionally much smaller than those in the other great apes, we can still see traces of their earlier importance, like these deep roots.
  11. In places you can see the trabecular internal structure of my mandible clearly. As someone who geeks out pretty much anytime I get a look inside a bone, this tickled me.
  12. The remains of an alveolus or tooth socket. I had my 3rd molars out almost a decade ago, and by now the sockets will have mostly filled in with new trabecular bone. But you can still see the ghostly outline of at least this one – a sort of morphogenetic trace fossil buried inside my mandible. I assume that in another decade or two this will have disappeared through regular bone remodeling.

Here’s a closeup of my left upper 2nd premolar and first two (and only remaining) molars. The gutta-percha filling the pulp cavities of the three roots of the 1st molar is obvious. The disparity in root length is mostly illusory – this was an oblique shot and the two ‘short’ roots are foreshortened.

Here’s the same image with the roots of the 2nd molar traced in pink, and the inferior margin of the maxillary sinus traced in blue. It’s not that uncommon for upper molar roots to stick up into the maxillary sinuses. That was true of my 3rd molars as well, and when I had them taken out, the endodontist had to put stitches into my gums to close the holes. Otherwise I would have had open connections between my oral cavity and maxillary sinuses, which would have sucked and been dangerous. Nasal mucus in the maxillary sinuses could have drained into my mouth, and food I was chewing could have been forced up into the sinuses, where it would have decomposed and caused a truly vile sinus infection.

In a developmental sense, it’s not that the roots of the teeth grow upward into the sinuses, it’s that the sinuses grow downward, eroding the bone around the roots of the teeth. This happens well after the teeth are done forming – the sinuses continue to expand as long as the skull is growing, and they retain the potential to remodel the surrounding bone for as long as we live. Even in cases like mine where the roots of the molars stick up into the sinuses, the tooth roots are still covered by soft tissue, including branches of the superior alveolar artery, vein, and nerve that enter the pulp cavities of the tooth roots through foramina at their tips.

If you ask your dentist for copies of your own dental x-rays, you’ll probably get them. If you do, have fun exploring the weird territory inside your head.

Reference

  • Moss, M. L. (1968). A theoretical analysis of the functional matrix. Acta Biotheoretica, 18(1), 195-202.

Upcoming book signings

April 19, 2017

Come gawk at this weirdo in public!

I’ll be signing copies of The Sauropod Dinosaurs: Life in the Age of Giants at regional events the next two weekends.

This this coming Saturday, April 22, I’ll be at the Inland Empire Science Festival, which will run from 10 AM to 4 PM at the Western Science Center in Hemet, California. There will be a ton of other special exhibits and activities, too. I don’t know all of them off the top of my head, but I know that Brian Engh will have the table next to mine, so come by and get two doses of awesome paleo art.

The following Friday, April 28, I’ll be at Beer N’ Bones 2017, which runs from 7-11 PM at the Arizona Museum of Natural History in Mesa, Arizona. In addition to signing books, I’ll also be in the “Speed Dating a Scientist” thing, where small groups of people get five minutes each at a table with a researcher, to ask whatever they want. Not just paleontologists, but scientists of all stripes. That said, I know of a couple of other local paleontologists who will also be there as guests – Andy Farke and Thierra Nalley. I was at Beer N’ Bones last year and it was a blast. As you might suspect from the name, it is 21-and-over only.

I’ll have books for sale – at a healthy discount – at both events. Hopefully I’ll see you out there.

This is very belated, but back in the summer of 2014 I was approached to write a bunch of sections — all of them to do with dinosaurs, naturally — in the book Evolution: The Whole Story. I did seven group overviews (Dinosauria overview, prosauropods, sauropods, stegosaurs, ankylosaurs, marginocephalians, and hadrosaurs), having managed to hand the theropod work over to Darren.

My author copy arrived in February 2016 (which, yes, is over a year ago. Your point?) It’s really nice:

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And at 576 heavy, glossy pages, it’s a hefty tome.

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My contribution was fairly minimal, really: I provided about 35 pages. Darren wrote a lot more of it. Still, I’m pleased to have been involved. It’s nicely produced.

Here a sample spread — the first two of a four-page overview of sauropods, showing some nice illustrations and a typical timeline across the bottom of the page.

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And here’s one of the ten “highlights” sections I did, mostly on individual dinosaurs. This is the best one, of course, based on sheer taxon awesomeness, since it deals with Giraffatitan:

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Unfortunately, not all of the artwork is of this quality. For example, the life restoration that graces my spread on Argentinosaurus makes me want to stab my own eyes out:

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Still, putting it all together, this is an excellent book, providing a really helpful overview of the whole tree of life, each section written by experts. It’s selling for a frankly ludicrous £16.55 in the UK — it’s easily worth two or three times that; and $30.24 in the US is also excellent value.

Highly recommended, if I do say it myself.