Late last year I got tapped by the good folks at Capstone Press to write a dinosaur book for their Mind Benders series for intermediate readers. Now it’s out. (In fact, it’s been out for a couple of months now, I’ve just been too busy with other things to get this post up.) Covers all the major groups and some of the minor ones, includes a timeline and evolutionary tree, 112 pages, $6.95 in paperback. Despite the short, punchy, 2-3 facts per critter format, I tried to pack in as many new findings and as much weird trivia as possible, so hopefully it won’t all be old news (facts chosen for the cover notwithstanding). Suggested age range is grades 1-6 but who knows what that means; one of the best reviews that Mark Hallett and I got for our big semi-technical sauropod tome was written by a 6-year-old. Many thanks to my editors at Capstone, Shelly Lyons and Marissa Bolte, for helping me get it over the finish line and wrangling about a trillion details of art and science along the way.

If you need a gateway drug or stocking stuffer for a curious kid, give it a look. Here’s the Amazon link (and for teachers, librarians, and my future reference, the publisher’s link).

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Please welcome Mirarce eatoni

November 13, 2018

Skeletal reconstruction of Mirarce by Scott Hartman (Atterholt et al. 2018: fig. 19). Recovered bones in white, missing bones in gray. The humerus is 95.9mm long.

Today sees the publication of the monster enantiornithine Mirarce eatoni (“Eaton’s wonderful winged messenger”) from the Kaiparowits Formation of Utah, by Jessie Atterholt, Howard Hutchinson, and Jingmai O’Connor. Not my critter, not my story, but it is SV-POW!-adjacent. (Just here for the paper? Here’s the link.)

Xiphoid process of sternum of Mirarce (Atterholt et al. 2018: fig. 5). Scale bar = 1cm.

As of this past summer, I knew that Jessie had a prehistoric monster coming out soon, and I knew that Brian Engh liked bringing prehistoric monsters to life, and I suspected that if the two reagents were combined, the rest of us might get something cool out of it.

Jessie and Brian talking about Mirarce, Utah for scale. July 13, 2018.

I did some heavy eavesdropping while the three of us were stomping around southern Utah looking for dinosaurs, so I got to hear Jessie and Brian batting ideas back and forth. By the end of our Utah trip Brian had sketches, and not long after, finished art (his post on Mirarce, including process sketches, is here). If you’ve seen one of my talks in the last month or so, you’ve gotten a teaser (with Jessie’s and Brian’s permission), and I know the piece got shown around a bit at SVP, too. You’ve waited long enough, here you go:

Not that the art is the whole story! Mirarce is a legitimately awesome find and Jessie and her coauthors poured a ton of work into the description. I’d tell you all about it, but much more capable and bird-fluent folks are on that already, and I have spinal cord and brainstem lectures to polish. So I’m gonna leave you with some links, which I’ll try to keep updated as different outlets get the story out:

Reference

Atterholt, J., Hutchinson, J.H.., and O’Connor, J.K. 2018. The most complete enantiornithine from North America and a phylogenetic analysis of the Avisauridae. PeerJ 6:e5910 https://doi.org/10.7717/peerj.5910

The more I look at the problem of how flexible sauropod necks were, the more I think we’re going to struggle to ever know their range of motion It’s just too dependent on soft tissue that doesn’t fossilise. Consider for example the difference between horse necks (above) and camel necks (below).

The skeletons of both consist of vertebrae that are pronouncedly opisthocoelous (convex in front and concave behind), so you might think their necks would be similarly flexible.

But the balls of horse cevicals are deeply embedded in their corresponding sockets, while those of camels have so much cartilage around and between them that the tip of the ball doesn’t even reach the rim of the socket. As a result of this (and maybe other factors), camel necks are far more flexible than those of horses.

Which do sauropod necks resemble? We don’t currently know, and we may never know. It will help if someone gets a good handle on osteological correlates of intervertebral cartilage.

 


[This post is recycled and expanded from a comment that I left on a Tetrapod Zoology post, but since Tet Zoo ate that comment it’s just as well I kept a copy.]

The Sunday after SVP, Brian Engh and I visited the museum in Albuquerque. I was quite taken with the mounted T. rex. It’s waaaay more interesting and dynamic than any other T. rex mount I’ve seen. It even beats the “Rockette rex” in Denver (which I really like and need to blog about), by virtue of putting the body and head down at eye level where you can study them up close.

The only thing I don’t like about this mount is that it has the dumb teeth-hanging-out-too-far thing going on. Why the heck people don’t fix that, I have no idea. Like, even if that’s the way the jaws are molded, cut off the excess and glue the crowns back up where they belong. Or fix the friggin’ mold. It’s not like the problem hasn’t been obvious for decades.

On the upside, pretty much everything else about this mount is awesome. Brian and I spent a fair amount of time working through the muscle attachments and thinking about how bulky the animal would have been in life. The answer is “very”.

Pretty cool to think that a fleshier, more aggro version of this was the last thing that many animals ever saw. And by ‘cool’ I mean ‘terrifying’.

Diverticulum, diverticula

November 4, 2018

This is not ‘Nam. This is Latin. There are rules.

The term for a small growth off an organ or body is diverticulum, singular, or diverticula, plural. There are no diverticulae or God forbid diverticuli, no matter what you might read in some papers. Diverticuli is a word – it’s the genitive form of diverticulum. But I’ve never seen it used that way in an anatomy or paleo paper. Diverticuli and diverticulae as alt-plurals for diverticulum are abominations that must be stomped out with extreme prejudice. If you want to get cute with alternative spellings, Wiktionary says you can use deverticulum. Wiktionary does not warn you that you will be mocked for doing so, but it is true nonetheless.

Stop jacking up straightforward anatomical terms, authors who should know better.

Here’s a swan. Unlike diverticuli and diverticulae, this unlikely morphology is real.

 

Coproliteposting time!

October 28, 2018

I wasted some time today making memes. I blame the Paleontology Coproliteposting group on Facebook.

Of course I started out by making fun of the most mockable sauropod. This one’s for you Cam-loving perverts out there. You know who you are.

This one was inspired by the thiccthyosaur meme, which irritatingly enough I cannot find right now. Oh no, wait, here it is.

I’m laughing through the tears.

For previous adventures in meme-ing, see this post.

In a comment on the last post, Mike wrote, “perhaps the pneumaticity was intially a size-related feature that merely failed to get unevolved when rebbachisaurs became smaller”.

Caudal pneumaticity in saltasaurines. Cerda et al. (2012: fig. 1).

Or maybe pneumaticity got even more extreme as rebbachisaurids got smaller, which apparently happened with saltasaurines  (see Cerda et al. 2012 and this post).

I think there is probably no scale at which pneumaticity isn’t useful. Like, we see a saltasaurine the size of a big horse and think, “Why does it need to be so pneumatic?”, as if it isn’t still one or two orders of magnitude more massive than an ostrich or an eagle, both of which are hyperpneumatic even though only one of them flies. Even parakeets and hummingbirds have postcranial pneumaticity.

Micro CT of a female Anna’s hummingbird. The black tube in the middle of the neck is the supramedullary airway. Little black dots in the tiny cervical centra are air spaces.

We’re coming around to the idea that the proper way to state the dinosaur size question is, “Why are mammals so lousy at being big on land?” Similarly, the proper way to state the pneumaticity question is probably not “Why is small sauropod X so pneumatic?”, but rather “Why aren’t some of the bigger sauropods even more pneumatic?”

Another thought: we tend to think of saltsaurines as being crazy pneumatic because they pneumatized their limb girdles and caudal chevrons (see Zurriaguz et al. 2017). Those pneumatic foramina are pretty subtle – maybe their apparent absence in other sauropod clades is just because we haven’t looked hard enough. Lots of things have turned out to be pneumatic that weren’t at first glance – see Yates et al. (2012) on basal sauropodomorphs and Wedel and Taylor (2013b) on sauropod tails, for example.

Back of the skull of a bighorn sheep, showing the air spaces inside one of the broken horncores.

Or, even more excitingly, if the absence is genuine, maybe that tells us something about sauropod biomechanics after all. Maybe if you’re an apatosaurine or a giant brachiosaurid, you actually can’t afford to pneumatize your coracoid, for example. One of my blind spots is a naive faith that any element can be pneumatized without penalty, which I believe mostly on the strength of the pneumatic horncores of bison and bighorn sheep. But AFAIK sauropod girdle elements don’t have big marrow cavities for pneumaticity to expand into. Pneumatization of sauropod limb girdles might have come at a real biomechanical cost, and therefore might have only been available to fairly small animals. (And yeah, Sander et al. 2014 found a pneumatic cavity in an Alamosaurus pubis, but it’s not a very big cavity.)

As I flagged in the title, this is noodling, not a finding, certainly not certainty. Just an airhead thinking about air. The comment thread is open, come join me.

References