A sauropod on Mars

February 24, 2021

This is old news, for those who have been following NASA’s Perseverance rover since before it left Earth, and it’s also not my find–my friend, colleague, and sometime co-author Brian Kraatz send me a heads-up about it this morning.

NASA posted the image above a couple of days ago, in a post called “Mastcam-Z looks at its calibration target“. If you zoom in, you can just make out a tiny silhouette of a sauropod on the ring around the MarsDial (what we call a sundial on Mars).

Here’s a much clearer pre-launch image from the Planetary Society (link), which helped design the calibration targets. Starting at about 7:00 and going around clockwise, there’s an image of the inner Solar System, with the Sun, Mercury, Venus, Earth, and Mars, then DNA, bacteria, a fern, a sauropod, humans (same silhouettes as on the Pioneer probes), a retro-style rocket ship, and finally a motto, “Two worlds, one beginning”, which may be a sly nod to the hypothesis that life in the inner Solar System started on Mars and was later seeded to Earth on meteorites–or possibly vice versa.

What’s with all this bling? It’s all about calibrating the cameras on Perseverance. The MarsDial gives the position and angle of the sun, and the colored dots help calibrate the color output of the cameras. There are other calibration targets for other cameras on board Perseverance, as well as some other technological ‘Easter eggs’ from the folks who designed and built the rover–read more about them here (link).

Perseverance is up there to explore “the potential of Mars as a place for life” (source), both past and future. Its four science objectives are:

  1. Looking for Habitability: Identify past environments capable of supporting microbial life.
  2. Seeking Biosignatures: Seek signs of possible past microbial life in those habitable environments, particularly in special rocks known to preserve signs of life over time.
  3. Caching Samples: Collect core rock and “soil” samples and store them on the Martian surface. [For a future sample-return mission.–MJW]
  4. Preparing for Humans: Test oxygen production from the Martian atmosphere.

Personally, I have my fingers firmly crossed that Perseverance finds something like this sticking out of a Martian rock:

(That one is actually from Utah, not Mars–see this post.) I don’t see any other way that my particular skill set is going to contribute to the exploration of the Solar System, which I’d really like to do. So I’ll wait, and watch Perseverance send back pictures, and wait some more. Sigh.

Anyway, there’s at least one sauropod on Mars, and that will have to do (for now!).

Bonus: if you haven’t watched the video of the rocket skycrane delivering the car-sized Perseverance to the surface of Mars, you need to. And if you have watched it, who cares, watch it again:

What if I told you that when Matt was in BYU collections a while ago, he stumbled across a cervical vertebra — one labelled DM/90 CVR 3+4, say — that looked like this in anterior view?

I think you would say something like “That looks like a Camarasaurus cervical, resembling as it does those illustrated in the beautiful plates of Osborn and Mook (1921)”. And then you might show me, for example, the left half of Plate LXII:

And then you might think to yourself that, within its fleshy envelope, this vertebra might have looked a bit like this, in a roughly circular neck:

Reasonable enough, right?

But when what if I then told you that in fact the vertebra was twice this wide relative to its height, and looked like this?

I’m guessing you might say “I don’t believe this is real. You must have produced it by stretching the real photo”. To which I would reply “No no, hypothetical interlocutor, the opposite is the case! I squashed the real photo — this one — to produce the more credible-seeming one at the top of the post”.

You would then demand to see proper photographic evidence, and I would respond by posting these three images (which Matt supplied from his 2019 BYU visit):

BYU specimen DM/90 CVR 3+4, cervical vertebra of ?Camarasaurus in anterior view. This is the photo from which the illustration above was extracted.

The same specimen in anteroventral view.

The same specimen in something approaching ventral view.

So what’s going on here? My first thought was that this speicmen has to have been dorsoventrally crushed — that this can’t be the true shape.

And yet … counterpoint: the processes don’t look crushed: check out the really nice 3d preservation of the neural spine metapophyses, the prezygs, the transverse processes, the nice, rounded parapophyseal rami, and even the ventral aspect of the centrum. This vertebra is actually in pretty good condition.

So is this real? Is this the vertebra more or less as it was in life? And if so, does that mean that the flesh envelope looked like this?

Look, I’m not saying it isn’t ridiculous; I’m just saying this seems to be more or less where the evidence is pointing. We’ve made a big deal about how the necks of apatosaurines were more or less triangular in cross-section, rather than round as has often been assumed; perhaps we need to start thinking about whether some camarasaur necks were squashed ovals in cross section?

Part of what’s crazy here is that this makes no mechanical sense. A cantilevered structure, such as a sauropod neck, needs to be tall rather than wide in order to attain good mechanical advantage that can take the stress imposed by the neck’s weight. A broad neck is silly: it adds mass that needs to be carried without providing high anchors for the tension members. Yet this is what we see. Evolution doesn’t always do what we would expect it to do — and it goes off the rails when sexual selection comes into play. Maybe female camarasaurus were just really into wide-necked males?

Final note: I have been playing fast and loose with the genus name Camarasaurus and the broader, vaguer term camarasaur. Matt and I have long felt (without having made any real attempt to justify this feeling) that Camarasaurus is way over-lumped, and probably contains multiple rather different animals. Maybe there is a flat-necked species in among them?

(Or maybe it’s just crushing.)

These things just catch my eye, I can’t help it.

Left: Oddbins corkscrew, circa 1997. Right: left femur of Patagotitan mayorum, circa 100,000,000 BC.

Note that the corkscrew features a distinct medially directed femoral head, the bulge in the lateral margin of the proximal portion that is characteristic of titanosaurs, and a straight shaft. OK, it’s missing tibial and fibular condyles at the distant end, but you can’t have everything.


The stupidest head

August 21, 2019

Left: Homo sapiens, head, neck and upper trunk in right lateral view (unprepared specimen). Right: Camarasaurus sp., skull in left lateral view. Photograph at the Natural History Museum of Utah, Salt Lake City, Utah. 2016.

Here’s a piece of signage from the wonderful Dinosaur National Monument, which we visited on the 2016 Sauropocalypse.

And in close-up:

This is the first and only time I’ve been encouraged to touch real dinosaur bones on the basis that a cast of them was too fragile.

Happily, we did have some great experiences with the actual fossils. Here is Matt, inspecting part of the wall, while our host Dan Chure documents the moment and the cotyle of a convenient ?Camarasaurus cervical acts as a receptacle for the cameras not in use at that point.

Above us, on the balcony, tourists wonder at such astonishingly massive creatures, and their ability to navigate a wall of fossils.

It’s a miracle!

June 30, 2019

I’ll see your face-of-the-blessed-virgin-in-a-waffle and raise you the fourth dorsal vertebra of the Giraffatitan brancai paralectotype BM.R.2181 (formerly HMN S II) in a dandelion leaf:

I saw this lying on the ground as my friend Nataley was playing a short set at a festival, and it immediately made me think of this:

Janensch (1950:Abb. 54). 17ter Präsakralwirbel (SII), Hinteransicht.

You’ll remember that we’ve been playing with CM 555, a subadult apatosaurine of indeterminate species, though John McIntosh assigned it to Brontosaurus (then Apatosaurus) excelsus. At the start of the week, we had the centra and neural arches of cervicals 1-14, plus there were some appendicular elements on a shelf that we’d not yet gone to. But then today, Matt found this drawer:

It contained a nice selection of cervical ribs that were part of the same specimen. Jackpot!

[You might notice that some of them have the specimen number 584 written on them. The history is that CM 555 and CM 584 came out of the same quarry, but most of the bones were initially thought to belong to a camarasaur which was designated CM 584. John McIntosh (1981:25) identified them as belonging to an apatosaurine, and they are now considered to be part of CM 555. The limb bones are catalogued separately as CM 556, but recognised as likely belonging to the same individual.]

Most of these ribs had field numbers written on them which were able to use to associate them with individual cervicals; and those that lacked these numbers, we could associate anyway, because the options were limited to a relatively small number of gaps. The upshot is that we know which vertebra each of these belongs to.

We have both ribs of C6, which is probably the best preserved single vertebra — centrum and arch — so I was able to rebuild the vertebra from its component parts. Matt was impressed:

And to be fair, I was pretty darned impressed myself:

Truly, this is a beautiful specimen. It was already pretty lovely, but putting the cervical ribs in place changed everything. It was totally transformed from a nice diplodocid cervical to an absolutely rock-solid slam-dunk apatosaurine — one to make grown men weep.

Here it is in right posterolateral view, just generally being awesome.


  • McIntosh, John S. 1981. Annotated catalogue of the dinosaurs (Reptilia, Archosauria) in the collections of Carnegie Museum of Natural History. Bulletin of the Carnegie Museum 18:1–67.


Four huge beasts

March 13, 2019

Left to right: Allosaurus fragilis, Apatosaurus louisae, Homo sapiens, Diplodocus carnegii.


March 13, 2019

Separated at birth.

Left: Apatosaurus lousiae holotype CM 2018, cast skull associated with specimen. Right: Matt Wedel. Scientists have long wondered how such a bloated beast could etc. etc.

(Matt’s photo, taken in the public gallery of the Carnegie Museum.)