When I was nine, a copy of Don Glut’s The New Dinosaur Dictionary turned up in my local Waldenbooks. It wasn’t my first dinosaur book, by far – I’d been a dinosaurophile since the age of three. But The New Dinosaur Dictionary was different.

Up to that point, I had subsisted on a heavy diet of kids’ dino books and the occasional article in National Geographic and Ranger Rick. The kids’ books were aimed at kids and the magazine articles were pitched at an engagingly popular level. I didn’t understand every word, but they were clearly written for curious layfolk, not specialists.

A typical spread from The New Dinosaur Dictionary (Glut, 1982). The armored sauropod blew my young mind.

The New Dinosaur Dictionary was something else entirely. It had photos of actual dinosaur bones and illustrations of skeletons with cryptic captions like, “Skeleton of Daspletosaurus torosus. (After Russell)”. Okay, clearly this Russell cove was out there drawing dinosaur skeletons and this book had reproduced some of them. But nobody I knew talked like that, and the books I had access to up to that point held no comparable language.

The New Dinosaur Dictionary (Glut, 1982: p. 271)

Then there was stuff like this: “The so-called Von Hughenden sauropod restored as a brachiosaurid by Mark Hallett”. A chain of fascinating and pleasurable ideas detonated in my brain. “The so-called” – say what now? Nobody even knew what to call this thing? Somehow I had inadvertently sailed right to the edge of human knowledge of dinosaurs, and was peering out into taxa incognita. “Restored as a brachiosaurid” – so this was just one of several possible ways that the animal might have looked. Even the scientists weren’t sure. This was a far cry from the bland assurances and blithely patronizing tones of all my previous dinosaur books.

“By Mark Hallett.” I didn’t know who this Hallett guy was, but his art was all over the book, along with William Stout and some guy named Robert T. Bakker and a host of others who were exploding my conception of what paleo art could even be. Anyway, this Mark Hallett was someone to watch, not only because he got mentioned by name a lot, but because his art had a crisp quality that teetered on some hypercanny ridge between photorealism and scribbling. His sketches looked like they might just walk off the page.

In case that line about scribbling sounds dismissive: I have always preferred sketches by my favorite artists to their finished products. The polished works are frequently inhumanly good. They seem to have descended in a state of completed perfection from some divine realm, unattainable by mere mortals. Whereas sketches give us a look under the hood, and show how a good artist can conjure light, shadow, form, weight, and texture from a few pencil strokes. Put it this way: I am anatomist by temperament first, and by training and occupation second. Of course I want to see how things are put together.

The New Dinosaur Dictionary (Glut, 1982: p. 75)

Anyway, The New Dinosaur Dictionary was something completely new in my experience. It wasn’t aimed at kids and written as if by kids, like lots of kids’ books. It wasn’t even written by adults talking down (deliberately or inadvertently) to kids, or trying to reach a wide audience that might include kids. It was written by an adult, aiming at other adults. And it was admitting in plain language that we didn’t know everything yet, that there were lots of animals trembling on the outer threshold of scientific knowledge. I didn’t understand half of it – I was down in an ontogenetic trench, looking up as these packets of information exploded like fireworks over my head.

In Seeing In the Dark, the best book about why you should go out stargazing for yourself, Timothy Ferris writes about growing up on Florida’s Space Coast in the early 1960s, and watching the first generation of artificial satellites pass overhead:

I felt like an ancient lungfish contemplating the land from the sea. We could get up there.

That’s precisely the effect that The New Dinosaur Dictionary had on me: I could get up there. Maybe not immediately. But there were steps, bodies of knowledge that could be mastered piecemeal, and most of all, mysteries to be resolved. The book itself was like a sketch, showing how from isolated and broken bones and incomplete skeletons, scientists and artists reconstructed the world of the past, one hypothesis at a time. Now I take it for granted, because I’ve been behind the curtain for a couple of decades. But to my 9-year-old self, it was revolutionary.

This has all come roaring back because of something that came in the mail this week. Or rather, something that had been waiting in the mailroom for a while, that I finally picked up this week: a package from Mark Hallett, enclosing a copy of his 2018 dinosaur calendar. And also this:

 

An original sketch, which he gave to me as a Christmas present. The published version appears on one of the final pages of our book, where we discuss the boundaries between the known – the emerging synthesis of sauropod biology that we hoped to bring to a broader audience by writing the book in the first place – and the unknown – the enduring mysteries that Mark and I think will drive research in sauropod paleobiology for the next few decades. Presented without a caption or commentary, the sketch embodies sauropods as we see them: emerging from uncertainty and ignorance one hard-won line at a time, with ever-increasing solidity.

Thank you, Mark, sincerely. That sketch, what it evokes, both for me now and for my inner 9-year-old – you couldn’t have chosen a better gift. And I couldn’t be happier. Except perhaps to someday learn that our book exploded in the mind of a curious kid the way that The New Dinosaur Dictionary did for me 34 years ago, a time that now seems as distant and romantic as the primeval forests of the Mesozoic.

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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

Hey sports fans, as the year winds down I bring you another podcast appearance. This time out I’m rolling with Mark Hallett, and we’re talking about sauropods through the lens of our still-plausibly-somewhat-newish book, The Sauropod Dinosaurs: Life in the Age of Giants, on the I Know Dino podcast. Many thanks to Sabrina and Garret for having us on the show. While you’re on that page, check out the nice preview of Mark’s 2018 dinosaur calendar, which is available at Pomegranate and Amazon.

The photo shows the Diplodocus carnegii cast mounted in the natural history museum in Vienna, one of Andrew Carnegie’s gifts to the world. A happy seasonal metaphor, sez me. Hope your new year is equally happy!

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!

This was an interesting exercise. It was my first time generating a poster to be delivered at a conference since 2006. Scientific communication has evolved a lot in the intervening decade, which spans a full half of my research career to date. So I had a chance to take the principles that I say that I admire and try to put them into practice.

It helped that I wasn’t working alone. Jann and Brian both provided strong, simple images to help tell the story, and Mike and I were batting ideas back and forth, deciding on what we could safely leave out of our posters. Abstracts were the first to go, literature cited and acknowledgments were next. We both had the ambition of cutting the text down to just figure captions. Mike nailed that goal, but my poster ended up being slightly more narrative. I’m cool with that – it’s hardly text-heavy, especially compared with most of my efforts from back when. Check out the text-zilla I presented at SVP back in 2006, which is available on FigShare here. I am happier to see, looking back, that I’d done an almost purely image-and-caption poster, with no abstract and no lit cited, as early as 1999, with Kent Sanders as coauthor and primary art-generator – that one is also on FigShare.

I took 8.5×11 color printouts of both my poster and Mike’s, and we ended up passing out most of them to people as we had conversations about our work. That turned out to be extremely useful – I had a 30-minute conversation about my poster at a coffee break the day before the posters even went up, precisely because I had a copy of it to hand to someone else. Like Mike, I found that presenting a poster resulted in more and better conversations than giving a talk. And it was the most personally relaxing SVPCA I’ve ever been to, because I wasn’t staying up late every night finishing or practicing my talk.

I have a lot of stuff to say about the conference, the field trip, the citability of abstracts and posters (TL;DR: I’m for it), and so on, but unfortunately no time right now. I’m just popping in to get this posted while it’s still fresh. Like Mike’s poster, this one is now published alongside my team’s abstract on PeerJ PrePrints.

I will hopefully have much more to say about the content in the future. This is a project that Jann, Brian, and I first dreamed up over a decade ago, when we were grad students at Berkeley. Mike provided the impetus for us to get it moving again, and kindly stepped aside when I basically hijacked his related but somewhat different take on ontogeny and serial homology. When my fall teaching is over, I’m hoping that the four of us can take all of this, along with additional examples found by Mike that didn’t make it into this presentation, and shape it into a manuscript. I’ll keep you posted on that. In the meantime, the comment field is open. For some related, previously-published posts, see this one for the baby sauropod verts, this one for CM 555, and this one for Plateosaurus.

Flying over Baffin Island on the way home.

And finally, since I didn’t put them into the poster itself, below are the full bibliographic references. Although we didn’t mention it in the poster, the shell apex theory for inferring the larval habits of snails was first articulated by G. Thorson in 1950, which is referenced in full here.

Literature Cited

 

Or, how a single lateral fossa becomes two foramina: through a finely graded series of intermediate forms. Darwin would approve. The ‘oblique lamina’ that separates the paired lateral foramina in C6 starts is absent in C2, but C3 through C5 show how it grows outward from the median septum. How do I know it grows outward, instead of being left behind during the pneumatization of the more posterior cervicals? Because with very few exceptions, all neosauropod cervicals start out with a single lateral fossa on each side, as illustrated in this post. But many of them end up with two or more foramina. Diplodocus is a nice example of this (from Hatcher 1901: plate 3):

I should clarify that the vertebrae above show that character transformation in this individual, at this point in its ontogeny. The vertebrae of CM 555 are about two-thirds the size of those of CM 3018, the holotype of A. louisae. In CM 3018, even C4 and C5 have completely divided lateral fossae, corresponding to the condition in C6 of CM 555.

As Mike and I discussed in our 2013 neural spine bifurcation paper, isolated sauropod cervicals require cautious interpretation because the morphology of the vertebrae changes so much along the series. The simple morphology of anterior cervicals reflects both earlier ontogenetic stages and more primitive character states. As Mike says, in sauropod necks, serial position recapitulates both ontogeny and phylogeny. So if you have a complete series, you can do something pretty cool: see the intermediate stages by which simple structures become complex.

If you’re thinking this might have something to do with my impending SVPCA poster, you’re right. Here’s the abstract.

For more on serially increasing complexity in sauropodomorph cervicals, see this post.

Here’s a dorsal vertebra of Camarasaurus in anterior view (from Ostrom & McIntosh 1966, modified by Wilson & Sereno 1998). It is one of the most disturbing things I have ever seen in a sauropod. It makes my skin crawl.

Here’s why: the centrum and the thing we habitually call the ‘neural arch’ aren’t fully fused, and as this modified version makes clear, the ‘neural arch’ is neither neural nor an arch. Instead of being bounded ventrally by the centrum and dorsally and laterally by the neural arch, the neural canal lies entirely below the synchondrosis between the not-really-an-arch and the centrum.

Why?! WHY WOULD YOU DO THAT, CAMARASAURUS? This is not ‘Nam. This is basic vertebral architecture. There are rules.

Look at c6 of Apatosaurus CM 555 here, behaving as all good vertebrae ought to. Neural arch be archin’, as the kids say.

And if you are seeking solace in the thought that maybe the artist just drew that Cam dorsal incorrectly, forget it. I’ve been to Yale and examined the original specimen. I’ve seen things, man!

Camarasaurus isn’t the only pervert around here. Check this out:

Unfused neural arch of a caudal vertebra of a juvenile Alamosaurus from Big Bend. And I mean, this is a neural arch. This may be the most neural of all neural arches, in that it contains the entire neural canal. It’s more of a neural…ring, I guess. That’s right, this Alamosaurus caudal is batting for the opposite team from the Cam dorsal above. And it’s a team that neither you nor I play on, because we have well-behaved normal-ass vertebrae with neural arches that actually arch, and then stop, like God and Richard Owen intended.

Scientifically, my question about these vertebrae is: well, that is, I mean to say, what!? I think they have damaged me in some fundamental way.

If you have anything more intelligent to add (or even less intelligent – consider the gauntlet thrown down!), the comment thread is open.

References

  • Ostrom, John H., and John S. McIntosh. 1966. Marsh’s Dinosaurs. Yale University Press, New Haven and London. 388 pages including 65 absurdly beautiful plates.
  • Wilson, J. A. and Paul C. Sereno. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Society of Vertebrate Paleontology, Memoir 5: 1-68.