An arresting image of an apatosaur vertebra

March 3, 2023

Here’s a cool photo of an apatosaur cervical in anterior view. This is from R. McNeill Alexander’s wonderful book Bones: The Unity of Form and Function, which was published in 1994. The whole book is packed with gorgeous full-color photos like this, and you can still get new copies for cover price (f’rinstance).

I remember stumbling across this image not long after I started working on sauropod vertebrae back in the late 90s, and being completely taken aback by the size of the cervical ribs. Up to that point I’d mostly been grokking the long, graceful cervicals of brachiosaurs, and the ridiculously overbuilt apatosaurine cervical morphology was a real kick in the brainpan. That’s well-trod ground here at SV-POW!, but this is still a beautiful photo. I suspect that the vertebra has been at least somewhat restored — some of the texturing on the condyle and under the diapophyses looks suspiciously like it was applied with tools or maybe just human fingers — but in general this is a pretty faithful representation of what an apatosaur cervical looks like from the front.

One thing that always strikes me about views like this is that you could take the centrum of this vertebra, strip off the neural arch and all the apophyses, and stick it through either one of the cervical ribs loops without scraping the sides. If life, the cervical rib loops held the (comparatively small) vertebral arteries and the (comparatively gigantic) intertransverse diverticula. We know this because that’s how birds are built, and because different apatosaurine specimens show pneumatic traces almost all the way around the inside of the cervical rib loop. The same is true in theropods like Majungasaurus, as Pat O’Connor showed in a lovely figure in his 2006 paper (O’Connor 2006: fig. 16). The volume of air in each of the paired cervical rib loops would have simply dwarfed the volume of air inside or even alongside the centrum. I wanted to visualize that better so I took my trusty old CT cross-section of OMNH 1094 and pasted it on top of this vert, stretching it a bit in GIMP to improve the fit:

Another thing that this photo shows nicely are the pneumatic fossae on the anterior surfaces of the cervical ribs. I’ve seen those features on loads of apatosaur cervical ribs, but I’ve never seen them discussed anywhere. I have thoughts on why those fossae are there, but that story will have to keep for another time.

References

 

Posted by Matt Wedel
Filed in Apatosaurus, Brontosaurus, cervical, cervical ribs, diplodocids, pneumaticity
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Apatosaurus cervical ribs and the tyranny of 2D images

December 8, 2022

Some quick backstory: lots of sauropods have long, overlapping cervical ribs, like the ones shown here in Sauroposeidon (diagram from this old post):

These long cervical ribs are ossified tendons of ventral neck muscles, presumably longus colli ventralis. We know they’re ossified tendons because of their bone histology (Klein et al. 2012), and we suspect that they’re longus colli ventralis because those tendons look the same in birds, just less ossified, as in this rhea (same specimens as these even older posts: 1, 2):

Diplodocoids have apomorphically short cervical ribs, which never extend very far past the end of their respective centra and sometimes don’t overlap at all. Still, we assume the long ventral neck muscles were there, just without long ossified tendons. Which brings me to Apatosaurus, which has cervical ribs that are anteroposteriorly short but famously massive, extending very below and/or to the sides of the cervical centra — for a truly breathtaking example see this post. Here are C3 through C7 in CM 3018, the holotype of Apatosaurus lousiae (Gilmore 1936: plate 24):

At least for me, it’s hard to resist the temptation to mentally scoot those vertebrae together into articulation, and imagine that the very swoopy-looking and maybe even down-turned cervical ribs allowed the ventral tendon bundles to wrap around the bottom of each cervical rib protuberance, something like this:

But it’s just not so, because like all 2D images, Gilmore’s plate distorts 3D reality. If you get to see the mounted skeleton in person, it’s clear that the cervical ribs are all more or less in line, and none of them are pointed at the big protuberances, which stick way out ventrolaterally.

Here I’ve drawn in the likely trajectories of the longus colli ventralis tendons. My little red pathways don’t precisely match the cervical ribs as mounted, but there’s a lot of distortion and restoration going on. For example, comparing with Gilmore’s plate we can see that the cervical ribs of C5, which point downward compared to all the others, only do that because someone forced them to — the whole anterior portion of the rib, where the shaft would actually join to the capitulum and tuberculum, is reconstructed. Even if I’m a little off, it’s clear that the cervical ribs shafts point backward, they’re all more or less in two parallel lines, and none of them point down and out toward the ventrolateral processes. The photo contains a mountain of useful morphological information that you’d never get from the lateral views.

My takeaways from all this:

  1. If a person has only seen 2D images of a specimen, and especially if those 2D images have only been orthogonal views with no obliques, their little island of knowledge is surrounded by at least a sizeable lake of ignorance, if not a small ocean.
  2. That doesn’t mean that seeing specimens in person is the only antidote — 3D models and 3D prints are extremely useful, and for specimens that are difficult to manipulate because of their size or fragility, they may be more useful than seeing or handling the specimen, at least for some questions.
  3. For Apatosaurus specifically, those ventrolateral processes cry out for explanation. They’re fairly solid knobs of bone that stick way out past the ossified tendons of the ventral-most neck muscles. That’s a super-weird — and super-expensive — place to invest a bunch of bone if you’re not using it for something fairly important, especially in a lineage that had just spent the last 80-100 million years making their necks as light as possible.
  4. Pursuant to that last point, we’re now in — ugh-ouch-shame — our 8th year of BrontoSMASH!!, with still just the one conference presentation to show for it (Taylor et al. 2015). Prolly time we got moving on that again.

References

Posted by Matt Wedel
Filed in #Brontosmash, Apatosaurus, Carnegie Museum, cervical, cervical ribs, diplodocids, mounts, museums, necks, rhea, stinkin' theropods
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Putative atlantal ribs of Diplodocus

November 23, 2022

Last time, I showed you a photo of the head and neck of the London Diplodocus and asked what was wrong. Quite a few of you got it right (including Matt when we were chatting, but I asked him not to give it away by posting a comment). The 100 SV-POW! dollars, with their cash value of $0.00, go to Orribec, who was the first to reply that the atlas (cervical 1) is upside-down.

Here is again, from the other side:

The Natural History Museum’s Carnegie Diplodocus cast, skull and anterior cervical vertebrae in left lateral view. Photograph by Mike Taylor.

I noticed this — when it seems the people putting up the skeleton did not, unless this is a deliberate joke — because I happened to be particularly tuned into atlas ribs at the time. You can see what appears a tiny rib hanging below the atlas, but no neural arch above it projecting up and back to meet the prezygapophyses of the axis (cervical 2). In fact the “cervical rib” on this left side is the neural arch of the right side, rotated 180 degrees about the axis of the neck.

Here’s how this should look, from the Carnegie Museum’s own Diplodocus:

The Carnegie Museum’s Diplodocus mount, skull and anterior cervical vertebrae in left lateral view. Photograph by Matt Lamanna.

In this picture, the atlas seems to be pretty much fused onto the axis, as seen in Gilmore (1936: figure 6) which Matt helpfully reproduced in Tutorial 36.

(Digression 1: you might think that this atlas is the real thing, since the Carnegie’s mount is the one with the real CM 84/94/307 material in it. But no: the atlas does not belong to any of those, which all lack this element. It seems to be a sculpture, but we can’t figure out what it’s based on.)

(Digression 2: you might notice that the London and Carnegie skulls are rather different. That’s because the London cast still has the original skull supplied in 1907, which is a sculpture based on CM 622 (rear) and USNM 2673 (the rest), while the Carnegie’s mount at some point had its skull replaced by a cast of CM 11161 — though no-one knows when.)

(Digression 3: the diplodocine originally catalogued as CM 662, on which the rear of the skull was based, was named as the holotype of a new species Diplodocus hayi by Holland (1924), traded to the Cleveland Museum of Natural History in 1956 where it was numbered CMNH 10670, then traded on the Houston Museum of Natural History in 1963 where istbecame HMNS 175, mounted in  Houston in 1975, remounted between 2013 and 2015, and finally moved to its own new genus Galeamopus by Tschopp et al. 2015. Yes, this stuff gets complicated.)

In fact, it’s amazing how much stuff we actually don’t know about these classic specimens, including the source of the atlas for both the Carnegie mount and the various casts — which are not the same. If only there was a single definitive publication that gathered everything that is known about these mounts. Oh well, maybe some day.

Now everyone knows that all the Carnegie Diplodocus mounts around the world were cast from the same molds, and so they all have the same altas <SCREEEECH> wait what?

The Muséum National d’Histoire Naturelle’s Carnegie Diplodocus cast, posterior part of skull and anterior cervical vertebrae in left lateral view. Photograph by Vincent Reneleau.

Here we are in Paris, and the atlas has these two honking great ribs. I have not seen these in any other Carnegie Diplodocus. I know they’re absent from the Berlin cast (thanks to Daniela Schwarz), from the Vernal re-cast (personal observation) and of course from the London cast. I would welcome observations (or even better, photos) from anyone who’s in a position to look at the Vienna, Bologna, Moscow, La Plata, Madrid or Mexico City casts.

So where did these atlas ribs come from? As with so much of this, no-one really knows. It’s especially mysterious as the Paris mount is supposed to be completely unchanged since its initial mounting. But some clue to the origin of the ribs in this mount is found in Holland (1906:249–250):

Accompanying the elements of the atlas sent to the writer for study by the kindness of Professor Osborn  [i.e. AMNH 969] are two bones, undoubtedly cervical ribs. They are both bones belonging on the right side of the centra. They are reported to have been found at the same place at which the atlas was found. The writer is inclined to think that the larger of these two bones (Fig. 20), was probably the rib of the atlas and indeed it requires but little effort to see that it might very well have served such a function, and that the smaller bone (Fig. 21) was the rib of the axis. Were the stump of the rib which remains attached to the axis in the Carnegie Museum, and which Mr. Hatcher has figured, removed, this smaller rib might take its place and would undoubtedly articulate very neatly to the facet

In case you’re too lazy to go and look at Holland’s illustrations for yourself, here they are.

The atlas rib:

The axis rib:

Holland went on:

In case the view entertained by the writer is correct, the form of the atlas and the axis with their attached ribs would be as given in the accompanying sketch (Fig. 22) rather than as given in the figure which has been published by Mr. Hatcher. Such a location of these parts has in its favor the analogy of the crocodilian skeleton.

Here is that composite atlas/axis complex:

(This arrangement with closely appressed atlas and axis ribs should ring a bell for anyone who’s looked much at croc necks, as for example in Taylor and Wedel 2013:figure 19.)

The atlas ribs on the Paris mount look a decent match for the one illustrated by Holland (1906:figure 20), so it seems a reasonable guess that they were sculpted based on that element. But that only leaves us with two more mysteries:

  1. Why do we see these atlas ribs only on the Paris cast, not in the Carnegie original or any of the other casts (that I know of)?
  2. Why does this cast have atlas ribs based on one of Holland’s elements, but not axis ribs based on the other?

Anyone?

References

 

Posted by Mike Taylor
Filed in atlas-axis complex, cervical, cervical ribs, Diplodocus, Natural History museum, necks, public galleries, stinkin' heads
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What’s wrong with this picture? No, really: what’s wrong?

November 21, 2022

Last Saturday I was at a wedding at Holy Trinity Brompton, a London church that is conveniently located a ten-minute stroll from the Natural History Museum. As I am currently working on a history paper concerning the Carnegie Diplodocus, I persuaded my wife, my eldest son and his fiancée to join me for a quick scoot around the “Dippy Returns” exhibition.

Here is a photo that I took:

Something is wrong here — and I don’t just mean the NHM exhibition’s stygian lighting.

Who can tell me what it is? $100 in SV-POW! Dollars(*) awaits the first person to get it right in the comments.

 

(*) Cash value: $0.00.

Posted by Mike Taylor
Filed in atlas-axis complex, cervical, cervical ribs, Diplodocus, Natural History museum, necks, public galleries, short, stinkin' heads
17 Comments »

Nature’s CT machine, part 2: an apatosaurine in the Salt Wash

January 28, 2020

In the last post, we looked at some sauropod vertebrae exposed in cross-section at our field sites in the Salt Wash member of the Morrison Formation. This time, we’re going to do it again! Let’s look at another of my faves from the field, with Thuat Tran’s hand for scale. And, er, a scale bar for scale:

And let’s pull the interesting bits out of the background:

Now, confession time. When I first saw this specimen, I interpeted it as-is, right-side up. The round thing in the middle with the honeycomb of internal spaces is obviously the condyle of a vertebra, and the bits sticking out above and below on the sides frame a cervical rib loop. I figured the rounded bit at the upper right was the ramus of bone heading for the prezyg, curved over as I’ve seen it in some taxa, including the YPM Barosaurus. And the two bits below the centrum would then be the cervical ribs. And with such big cervical rib loops and massive, low-hanging cervical ribs, it had to an apatosaurine, either Apatosaurus or Brontosaurus.

Then I got my own personal Cope-getting-Elasmosaurus-backwards moment, courtesy of my friend and fellow field adventurer, Brian Engh, who proposed this:

Gotta say, this makes a lot more sense. For one, the cervical ribs would be lateral to the prezygs, just as in, oh, pretty much all sauropods. And the oddly flat inward-tilted surfaces on what are now the more dorsal bones makes sense: they’re either prezyg facets, or the flat parts of the rami right behind the prezyg facets. The missing thing on what is now the right even makes sense: it’s the other cervical rib, still buried in a projecting bit of sandstone. That made no sense with the vert the other way ’round, because prezygs always stick out farther in front than do the cervical ribs. And we know that we’re looking at the vert from the front, otherwise the backwards-projecting cervical rib would be sticking through that lump of sandstone, coming out of the plane of the photo toward us.

Here’s what I now think is going on:

I’m still convinced that the bits of bone on what is now the left side of the image are framing a cervical rib loop. And as we discussed in the last post, the only Morrison sauropods with such widely-set cervical ribs are Camarasaurus and the apatosaurines. So what makes this an apatosaurine rather than a camarasaur? I find several persuasive clues:

  • If we have this thing the right way up, those prezygs are waaay up above the condyle, at a proportional distance I’ve only seen in diplodocids. See, for example, this famous cervical from CM 3018, the holotype of A. louisae (link).
  • The complexity of the pneumatic honeycombing inside the condyle is a much better fit for an apatosaurine than for Camarasaurus–I’ve never seen that level of complexity in a camarasaur vert.
  • The bump on what we’re now interpreting as the cervical rib looks suspiciously like one of the ventrolateral processes that Kent Sanders and I identified in apatosaurine cervicals back in our 2002 paper. I’ve never seen them, or seen them reported, in Camarasaurus–and I’ve been looking.
  • Crucially, the zygs are not set very far forward of the cervical ribs. By some rare chance, this is pretty darned close to a pure transverse cut, and the prezygs, condyle (at its posterior extent, anyway), and the one visible cervical rib are all in roughly the same plane. In Camarasaurus, the zygs strongly overhang the front end of the centrum in the cervicals (see this and this).

But wait–aren’t the cervical ribs awfully high for this to be an apatosaurine? We-ell, not necessarily. This isn’t a very big vert; max centrum width here is 175mm, only about a third the diameter of a mid-cervical from something like CM 3018. So possibly this is from the front of the neck, around the C3 or C4 position, where the cervical ribs are wide but not yet very deep. You can see something similar in this C2-C5 series on display at BYU:

Or, maybe it’s just one of the weird apatosaurine verts that has cervical rib loops that are wide, but not very deep. Check out this lumpen atrocity at Dinosaur Journey–and more importantly, the apatosaur cervical he’s freaking out over:

UPDATE just a few minutes later: Mike reminded me in the comments about the Tokyo apatosaurine, NSMT-PV 20375, which has wide-but-not-deep cervical ribs. In fact, C7 (the vertebra on the right in this figure) is a pretty good match for the Salt Wash specimen:

UpchurchEtAl2005-apatosaurus-plate2-C3-6-7

NSMT-PV 20375, cervical vertebrae 3, 6 and 7 in anterior and posterior views. Modified from Upchurch et al. (2005: plate 2).

UPDATE the 2nd: After looking at it for a few minutes, I decided that C7 of the Tokyo apatosaurine was such a good match for the Salt Wash specimen that I wanted to know what it would look like if it was similarly sectioned by erosion. In the Salt Wash specimen, the prezygs are sticking out a little farther than the condyle and cervical rib sections. The red line in this figure is my best attempt at mimicking that erosional surface on the Tokyo C7, and the black outlines on the right are my best guess as to what would be exposed by such a cut (or pair of cuts). I’ve never seen NSMT-PV 20375 in person, so this is just an estimate, but I don’t think it can be too inaccurate, and it is a pretty good match for the Salt Wash specimen.

Another way to put it: if this is an apatosaurine, everything fits. Even the wide-but-not-low-hanging cervical ribs are reasonable in light of some other apatosaurines. If we think this is Camarasaurus just because the cervical ribs aren’t low-hanging, then the pneumatic complexity, the height of the prezygs, and the ventrolateral process on the cervical rib are all anomalous. The balance of the evidence says that this is an apatosaurine, either a small, anterior vert from a big one, or possibly something farther back from a small one. And that’s pretty satisfying.

One more thing: can we take a moment to stand in awe of this freaking thumb-sized cobble that presumably got inside the vertebra through one its pneumatic foramina and rattled around until it got up inside the condyle? Where, I’ll note, the internal structure looks pretty intact despite being filled with just, like, gravel. As someone who spends an inordinate amount of time thinking about how pneumatic vertebrae get buried and fossilized, I am blown away by this. Gaze upon its majesty, people!

This is another “Road to Jurassic Reimagined, Part 2″ post. As before, Part 1 is here, Part 2 will be going up here in the near future. As always, stay tuned.

References

Posted by Matt Wedel
Filed in #JurassicReimagined, Apatosaurus, Brontosaurus, BYU Museum of Paleontology, cervical, cervical ribs, cross sections, Dinosaur Journey Museum of Western Colorado, diplodocids, field photos, hands used as scale bars, I'm stupid, Morrison Formation, museums, stinkin' appendicular elements, stinkin' mammals, stinkin' SV-POW!sketeers
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How our week at the Carnegie Museum went

March 17, 2019

In a word, amazingly. After 6 days (counting public galleries last Sunday), 4300 photos, 55 videos, dozens of pages of notes, and hundreds of measurements, we’re tired, happy, and buzzing with new observations and ideas.

We caught up with some old friends. Here Mike is showing an entirely normal and healthy level of excitement about meeting CM 584, a specimen of Camarasaurus from Sheep Creek, Wyoming. You may recognize this view of these dorsals from Figure 9 in our 2013 PeerJ paper.

We spent an inordinate amount of time in the public galleries, checking out the mounted skeletons of Apatosaurus and Diplodocus (and Gilmore’s baby Cam, and the two tyrannosaurs, and, and…).

I had planned a trip to the Carnegie primarily to have another look at the Haplocanthosaurus holotypes, CM 572 and CM 879. I was also happy for the chance to photograph and measure these vertebrae, CM 36034, which I think have never been formally described or referred to Haplocanthosaurus. As far as I know, other than a brief mention in McIntosh (1981) they have not been published on at all. I’m planning on changing that in the near future, as part of the larger Haplocanthosaurus project that now bestrides my career like a colossus.

The real colossus of the trip was CM 555, which we’ve already blogged about a couple of times. Just laying out all of the vertebrae and logging serial changes was hugely useful.

Incidentally, in previous posts and some upcoming videos, we’ve referred to this specimen as Brontosaurus excelsus, because McIntosh (1981) said that it might belong to Apatosaurus excelsus. I was so busy measuring and photographing stuff that it wasn’t until Friday that I realized that McIntosh made that call because CM 555 is from the same locality as CM 563, now UWGM 15556, which was long thought to be Apatosaurus excelsus but which is now (i.e., Tschopp et al. 2015) referred to Brontosaurus parvus. So CM 555 is almost certainly B. parvus, not B. excelsus, and in comparing the specimen to Gilmore’s (1936) plates of CM 563, Mike and I thought they were a very good match.

Finding the tray of CM 555 cervical ribs was a huge moment. It added a ton of work to our to-do lists. First we had to match the ribs to their vertebrae. Most of them had field numbers, but some didn’t. Quite a few were broken and needed to be repaired – that’s what I’m doing in the above photo. Then they all had to be measured and photographed.

It’s amazing how useful it was to be able to reassociate the vertebrae with their ribs. We only did the full reassembly for c6, in part because it was the most complete and perfect of all of the vertebrae, and in part because we simply ran out of time. As Mike observed in his recent post, it was stunning how the apatosaurine identity of the specimen snapped into focus as soon as we could see a whole cervical vertebra put back together with all of its bits.

We also measured and photographed the limb bones, including the bite marks on the radius (above, in two pieces) and ulna (below, one piece). Those will of course go into the description.

And there WILL BE a description. We measured and photographed every element, shot video of many of them, and took pages and pages of notes. Describing even an incomplete sauropod skeleton is a big job, so don’t expect that paper this year, but it will be along in due course. CM 555 may not be the most complete Brontosaurus skeleton in the world, but our ambition is to make it the best-documented.

In the meantime, we hopefully left things better documented than they had been. All of the separate bits of the CM 555 vertebrae – the centra, arches, and cervicals ribs – now have the cervical numbers written on in archival ink (with permission from collections manager Amy Henrici, of course), so the next person to look at them can match them up with less faffing about.

We have people to thank. We had lunch almost every day at Sushi Fuku at 120 Oakland Avenue, just a couple of blocks down Forbes Avenue from the museum. We got to know the manager, Jeremy Gest, and his staff, who were unfailingly friendly and helpful, and who kept us running on top-notch food. So we kept going back. If you find yourself in Pittsburgh, check ’em out. Make time for a sandwich at Primanti Bros., too.

We owe a huge thanks to Calder Dudgeon, who took us up to the skylight catwalk to get the dorsal-view photos of the mounted skeletons (see this post), and especially to Dan Pickering, who moved pallets in collections using the forklift, and moved the lift around the mounted skeletons on Tuesday. Despite about a million ad hoc requests, he never lost patience with us, and in fact he found lots of little ways to help us get our observations and data faster and with less hassle.

Our biggest thanks go to collections manager Amy Henrici, who made the whole week just run smoothly for us. Whatever we needed, she’d find. If we needed something moved, or if we needed to get someplace, she’d figure out how to do it. She was always interested, always cheerful, always helpful. I usually can’t sustain that level of positivity for a whole day, much less a week. So thank you, Amy, sincerely. You have a world-class collection. We’re glad it’s in such good hands.

What’s next? We’ll be posting about stuff we saw and learned in the Carnegie Museum for a long time, probably. And we have manuscripts to get cranking on, some of which were already gestating and just needed the Carnegie visit to push to completion. As always, watch this space.

References

Posted by Matt Wedel
Filed in Apatosaurus, Brontosaurus, camarasaurs, Carnegie Museum, caudal, cervical, cervical ribs, collections, diplodocids, Diplodocus, dorsal, Haplocanthosaurus, mounts, museums, notebook, public galleries, radius, stinkin' appendicular elements, stinkin' mammals, stinkin' SV-POW!sketeers, ulna
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Everything’s better with cervical ribs

March 15, 2019

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.

References

  • 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.

 

Posted by Mike Taylor
Filed in Apatosaurus, cervical, cervical ribs, collections, goofy
13 Comments »

Apatosaurus is — still — Just Plain Wrong

November 30, 2018

We’ve posted a lot here about how crazy the cervical vertebrae of apatosaurines are (for example: 1, 2, 3), and especially the redonkulosity of their cervical ribs. But I think you will agree with me that this is still an arresting sight:

That’s MWC 1946, a mid-cervical from the Mygatt-Moore Quarry that was figured by Foster et al. (2018: fig. 18 A-B) and referred with the rest of the Mygatt-Moore apatosaur material to Apatosaurus cf. louisae (entirely correctly, in my view). This is a ventral view, with the condyle down by the scale bar.

Here’s the same thing cropped from the background to emphasize its unbelievableness:

and mirrored and restored a bit in GIMP to give a taste of its probable appearance in life (if you had an apatosaur, an x-ray machine, and a lot of confidence about not getting stepped on):

For obvious reasons, my nickname for this specimen is the Brontosmasher.

Keep in mind that the centrum was full of air in life, whereas the cervical ribs and the bony struts that support them are just huge slabs of bone. I strongly suspect that the volume of bone in the cervical ribs and their supporting struts is vastly more than in the centrum and neural arch. I will soon have the ability to test that hypothesis–I have this specimen on loan from Dinosaur Journey for CT scanning and 3D modeling. Watch this space.

Many thanks to Julia McHugh at Dinosaur Journey for access to the specimen and assistance during my frequent visits.

Reference

  • Foster, J.R., Hunt-Foster, R.K., Gorman, M.A., II, Trujillo, K.C., Suarez, C.A., McHugh, J.B., Peterson, J.E., Warnock, J.P., and Schoenstein, H.E. 2018. Paleontology, taphonomy, and sedimentology of the Mygatt-Moore Quarry, a large dinosaur bonebed in the Morrison Formation, western Colorado—implications for Upper Jurassic dinosaur preservation modes: Geology of the Intermountain West 5: 23–93.
Posted by Matt Wedel
Filed in #Brontosmash, Apatosaurus, cervical, cervical ribs, collections, Dinosaur Journey Museum of Western Colorado, diplodocids, Just Plain Wrong, museums
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Did apatosaurs have unusually large neural spines, too?

June 22, 2018

We all know that apatosaurines have big honkin’ cervical ribs (well, most of us know that). But did they also have unusually large neural spines?

The question occurred to me the other day when I was driving home from work. I was thinking about C10 of CM 3018, the holotype of Apatosaurus louisae, and I thought, “Man, that is a lot of neural spine right there.”

Why was I thinking about C10, particularly? I traced and also stacked Gilmore’s (1936) drawing for my 2002 paper with Kent Sanders, and recycled the trace for my 2007 prosauropod paper, and recycled the stack-o-C10s for my 2013 PeerJ paper with Mike. So for better or worse C10 is my mental shorthand for A. louisae, the same way that their respective C8s seem to capture the essence of Giraffatitan and Sauroposeidon.

I decided that the quick-and-dirty solution was to compare the vertebrae of A. louisae with those of Diplodocus carnegii, the default reference diplodocid, and see how they stacked up. With the cotyles scaled to the same vertical diameters, this is what we get for C9 and C10 of CM 3018 (lighter gray, background, traced from Gilmore 1936) vs CM 84/94 (darker gray, foreground, traced from Hatcher 1901):

The A. louisae verts are a hair taller, proportionally, than those of D. carnegii, but not by much. The difference is trivial compared to the differences in centrum length and cervical rib size.

So where did I get this apparently erroneous impression that Apatosaurus had giant neural spines? Maybe it’s not that the neural spines of apatosaurines in particular are so large, but rather than diplodocids of all types have large neural spines compared to non-diplodocids. Here are the same vertebrae compared for D. carnegii (dark gray, background) and Camarasaurus supremus (black, foreground, traced from Osborn and Mook 1921):

I deliberately picked the longest C9 in the AMNH collection, and the least-distorted C10. The first surprise for me was how well this C. supremus C9 hangs with D. carnegii in terms of proportions. That is one looooong Cam vert. In any other sauropod, it would probably be beautiful. But because it’s Camarasaurus it attained its length in the most lumpen possible way, with the diapophysis way up front, the neural spine apex way at the back, and in the middle just…more vertebra. Like a stretch limo made from a Ford Pinto, or Mike’s horrifying BOBA-horse.

Inevitable and entirely justified Cam-bashing aside, it’s striking how much smaller the whole neural arch-and-spine complex is in C. supremus than in D. carnegii. And remember that D. carnegii is itself a bit smaller than Apatosaurus, spine-wise. Is this maybe a diplodocoid-vs-macronarian thing, at least in the Morrison? Here’s the C10 stack with Brachiosaurus included, represented by BYU 12867 (which I think is probably a C10 based on both centrum proportions and neural spine shape – see Wedel et al. 2000b for details), and with labels added because it’s getting a little nuts:

I like this; it shows a lot. Here are some things to note:

  • The diplodocids don’t just have taller neural spines, their pre- and postzygapophyses are also higher than in the macronarians. That’s gotta mean something, right? All else being equal, putting the zygs farther from the intervertebral joints would reduce the flexibility of the neck. Maybe diplodocoids could get away with it because they had more cervicals, or maybe their necks were stiffened for some reason.
  • The zygs being set forward of their respective centrum ends in the macronarians really comes through here.
  • The Brachiosaurus vert isn’t that different from a stretched (and de-uglified) Cam vert, with a slightly higher neural spine to help support the longer neck. (Maybe this is why Cam inspires such visceral revulsion: it reads as a failed brachiosaur.)
  • This emphasizes the outlier status of Apatosaurus in the cervical rib department. It bears repeating: the cervical ribs of Camarasaurus are certainly wide, but they’re not nearly as massive or ventrally expanded as in apatosaurines.

So far, pretty interesting. I’d like to add Barosaurus and Haplocanthosaurus to round out the “big six” Morrison sauropods. I known Haplo has big, tall, almost apatosaurine neural spines (as shown above, with arrows highlighting the epipophyses), but for Baro I’d have to actually do the comparison to see where it falls out.

The idea of bringing in Barosaurus also forces the question, previously glossed over, of how legit it is to compare C10s of all these animals when their cervical counts differed. C. supremus is thought to have had 12 vertebrae in its neck, Brachiosaurus 13 (based on Giraffatitan), A. louisae and D. carnegii 15, and Barosaurus probably 16. It would be more informative to graph neural spine height divided by cotyle diameter along the column for all of these critters, plus Kaatedocus and Galeamopus. But that’s a lot of actual work, and as much fun as it sounds (really, I’d rather be doing that), I have summer teaching to prep for and field gear to wrangle. So I’ll have to revisit this stuff another time.

References

Posted by Matt Wedel
Filed in Apatosaurus, brachiosaurids, Brachiosaurus, camarasaurs, cervical, cervical ribs, diplodocids, Diplodocus
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In quest of monsters – last week’s Utah adventure

May 17, 2018

Last Wednesday, May 9, Brian Engh and I bombed out to Utah for a few days of paleo adventures. Here are some highlights from our trip.

We started at a Triassic tracksite on Thursday. But I’m not going to post any pictures of the tracks – those will be coming to a Brian Engh joint near you in the future. Instead, I’m going to talk about this little male collared lizard whose territory included the tracksite. He was fearless – didn’t want to run off and leave us yahoos wandering around his patch of desert unsupervised. Brian tickled his chin at one point.

Getting this close to him is how I got shots like this one:

Click through to the big version, it’s worth it.

One more shot of a couple of cool desert dwellers. I was so fixated on the lizard that I didn’t realize until later that Brian was in the frame, taking a much-needed hydration break.

On Friday we had a temporary breaking of the fellowship. I went to Fruita, Colorado, to visit the Dinosaur Journey museum. You’ve seen photos from DJ here before, from the 2014 Mid-Mesozoic Field Conference and the 2016 Sauropocalypse. Here’s an apatosaur pubis with some obvious bite marks on the distal end. This is on display next to a similarly-bitten ischium, which is shown in the MMFC14 post linked above.

Here’s a big apatosaur cervical, in antero-ventral view, with a dorsal rib draped over its left side. The cervical ribs are not fused in this specimen, so it was probably still growing. Here’s a labeled version:

The short centrum and nearly-vertical transverse processes indicate that this is a pretty posterior cervical, possibly a C13 or thereabouts. This specimen was over the fence in the exhibit area and I couldn’t throw a scale bar at it, but I’d describe it as “honkin'”. Like most of the apatosaur material at DJ, this vert is from the Mygatt-Moore Quarry.

Of course the real reason I was at Dinosaur Journey was to see the Snowmass Haplocanthosaurus that John Foster and I described back in 2014. You may remember that its caudal vertebrae have wacky neural canals. You may also have noticed a recent uptick in the number of posts around here about wacky neural canals. The game is afoot.

But as cool as they were, the Triassic tracks, the collared lizard, and even the Snowmass Haplo were only targets of opportunity. Brian and I had gone to Utah for this:

That photo was taken by Paige Wiren of Salt Lake City, on the day that she discovered that bone eroding out of a riverbank, just as you see it.

Here’s Paige with the element, which proved to be the left femur of an apatosaurine sauropod. It’s face down in these photos, so we’re looking at the medial side. The articular head is missing from the proximal end – it should be facing toward Paige’s right knee in the above photo – but other than that and a few negligible nicks and dings, the femur was complete and in really good shape.

Paige did the right thing when she found the femur: she contacted a paleontologist. Specifically, she asked a friend, who in turn put her in touch with Carrie Levitt-Bussian, the paleontology Collections Manager at the Natural History Museum of Utah. Based on Paige’s photos and maps, Carrie was able to identify the element as a dinosaur femur, probably sauropod, within the territory of the BLM Hanksville Field Office. John Foster, the Director of the Museum of Moab, has a permit to legally collect vertebrate fossils from that area, and he works on sauropods, so Carrie put Paige in touch with John and with ReBecca Hunt-Foster, the district paleontologist for the BLM’s Canyon Country District in Utah.

Now, I know there’s a lot of heated rhetoric surrounding the Bureau of Land Management, but whatever your political bent, remember this: those are our public lands. Therefore the fossils out there are the collective property of all of us, and we should all be upset if they get poached or vandalized. Yes, that is a big problem – the Brontomerus type quarry was partially poached before the bones we have now were recovered, and vandalism at public fossil sites in Utah made the national news while we were out there.

So that’s what we went to do: salvage this bone for science and education before it could be lost to erosion or asshats. Brian and I were out there to assist John, ReBecca, and Paige, who got to see her find come out of the ground and even got her hands dirty making the plaster jacket. Brian and John headed out to the site Friday morning and met up with Paige there, and ReBecca and I caravanned out later in the day, after I got back from Fruita.

But I’m getting ahead of myself a bit. We didn’t have to jacket the whole thing. It had naturally broken into three pieces, with thin clay infills at the breaks. So we just slid the proximal and middle thirds away as we uncovered them, and hit any loose-looking pieces with consolidant. The distal third was in more questionable shape, so we did make a partial jacket to hold it together.

We also got to camp out in gorgeous country, with spectacular (and welcome) clouds during the day and incredible starry skies at night.

We floated the femur out of the site using the Fosters’ canoe at the end of the day on Saturday, and loaded up to head back to Moab on Sunday. At one point the road was empty and the sky was not, so I stood on the center line and took some photos. This one is looking ahead, toward I-70 and Green River.

And this one is looking behind, back toward Hanksville.

Here are John and Brian with the femur chunks in one of the back rooms of the Museum of Moab. The femur looks oddly small here, but assembled it was 155 cm (5’1″) long and would have been 160 (5’3″) or more with the proximal head. Smaller than CM 3018 and most of the big mounted apatosaurs, but nothing to sneeze at.

What happens to it next? It will be cleaned, prepped, and reassembled by the volunteers and exhibit staff at the Museum of Moab, and eventually it will go on public display. [Update, 19 October 2021: it is now on display!] Thousands of people will get to see and learn from this specimen because Paige Wiren made the right call. Go thou and do likewise.

That was the end of the road for the femur (for now), but not for Brian and me. We had business in Cedar City and St. George, so we hit the road Sunday afternoon. Waves of rainclouds were rolling east across Utah while we were rolling west, with breaks for sunlight in between. I miiiight have had to swerve a couple of times when all the scenery distracted me from driving, and I definitely made an obnoxious number of stops to take pictures.

I don’t remember which scenic overlook this was, but it was a pretty darned good view. This is another one that will reward embiggening – check out those mesas marching off into the distance.

In Cedar City we were guests of Andrew R.C. Milner, Site Paleontologist and Curator at the St. George Dinosaur Discovery Site at Johnson Farm (SGDS). We spent most of Monday at SGDS, getting our minds comprehensively blown by the amazing trace and body fossils on display. It was my first time visiting that museum, but it sure as heck won’t be the last.

I didn’t take nearly enough photos in St. George – too busy helping Brian do some filming for a future project – but I did get this gem. This is a Eubrontes track, from a Dilophosaurus-sized theropod. This is a positive track, a cast of the dinosaur’s foot made by sandy sediment that filled the natural mold formed when the dino stepped into mud. The high clay content of the mud recorded the morphology of the foot in fine detail, including the bumps of individual scales on the foot pads. The vertical streaks were cut into the side of the track by similar scales as the animal’s foot pushed into the mud.

The full story of the Johnson Farm tracks and trackmakers is beautifully told in the book Tracks in Deep Time: The St. George Dinosaur Discovery Site at Johnson Farm, by Jerry Harris and Andrew Milner. I hadn’t read it before, so I picked up a copy in the gift shop and I’ve been devouring it. As a professional scientist, educator, and book author myself, I’m jealous of what Jerry and Andrew produced – both the text and the abundant full-color illustrations are wonderfully clear, and the book is well-produced and very affordable.

From St. George we hit the road home, and rolled into Claremont just before midnight on Monday. It was a whirlwind tour – 1800 miles, three museums, and two fossil sites in six days – and my brain is still fizzing with all of the things we got to see and do.

One of the many pros of having a professional artist as a friend is that minimal hospitality, like letting him crash on my couch, is sometimes rewarded with original art. Brian was already gone when I got up Tuesday morning, but this was waiting for me on the dining room table. (Want your own? Help Brian make more monsters here.)

I owe plenty of thanks myself: to the Foster and Milner families for their near-maximal hospitality, to Julia McHugh of Dinosaur Journey for assistance in collections, to Diana Azevedo, Jalessa Spor, Jerry Harris, and the rest of the SGDS staff for being such gracious hosts, to Brian for being such a great friend and traveling companion, and most of all to Paige Wiren for finding the apato femur and helping us save it for science. You’re all top-notch human beings and I hope our paths cross again soon.

Posted by Matt Wedel
Filed in Apatosaurus, Art, Brian Engh, caudal, cervical, cervical ribs, Dinosaur Journey Museum of Western Colorado, diplodocids, field photos, Haplocanthosaurus, monsters, museums, People we like, pubis, stinkin' appendicular elements, stinkin' every thing that's not a sauropod, stinkin' lizards, stinkin' mammals, stinkin' SV-POW!sketeers, travel
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