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:


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


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.