Here at SV-POW! Towers, we’re keenly aware that some of our fans are just here for the hardcore sauropod vertebra action. These folks start to shift in their seats when we put up too many posts in a row on open access or rabbits or…okay, mostly just OA and bunnies. If that’s you – or, heck, even if it isn’t – your good day has come. Saddle up. Let’s ride.

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When Brian Engh and I were at the new Natural History Museum of Utah recently, I spotted this cute little juvenile cervical in one of the display cases.

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According to this sign, it’s UMNH 21054, and it was found by Frank DeCourten and prepared by Virginia Tidwell.

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It shares a display case and a sign with what is probably an anterior dorsal, UMNH 21055.

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Now, I don’t mean to brag (okay, maybe a little…) but the number of EKNApod* vertebrae is not large and the number of EKNApod vertebrae I’m not intimately familiar with hovers near zero. This thing was ringing bells – I knew I’d seen it before.

* Early Cretaceous North American sauropod

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Here are few more views. Note the light-colored oblong spot on the top of the condyle in the image above – this may be a pneumatic foramen filled with matrix, or a spot where the cortical bone flaked away to reveal one of the internal pneumatic spaces. Also, check out the fragment of extraneous bone (probably cervical rib) stuck sideways across the top of the centrum, just behind the condyle, in the image immediately below. Both of these features will be important later.

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The vert belongs to a juvenile sauropod because the neural arch is missing – it didn’t fuse to the centrum before the animal died. But it was a big baby; the centrum is maybe just a hair under 40 cm in length, meaning that a world-record giraffe might just maybe have a couple of cervicals of the same length. But basal titanosauriforms typically have 12-13 cervicals, not the whimpy 7 that almost all mammals must make do with, and all-stars like Euhelopus can have up to 17.

Also, this was not from the middle of the neck. No way. The parapophyses are huge, and the centrum is pretty stubby compared to Sauroposeidon or YPM 5294, the Sauroposeidonesque cervical from Unit VII of the Cloverly (pic here). My guess is we’re looking at something past the middle of the neck, where the cervicals start to get proportionally shorter (but sometimes max out in absolute length), maybe a C9 or C10. In Giraffatitan brancai HM SII/MB.R.2181, C10 has a centrum length of 100 cm and makes up about 12% of the 8.5-meter neck. Assuming similar proportions here, UMNH  21054 came from the roughly 3-meter neck of a sauropod about the size of a really big draft horse or a really small elephant.

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But enough noodling about the animal’s size. I knew I’d seen this vert before, but where? Thank goodness for comprehensive signage – I knew the material had been discovered by Frank DeCourten and prepped by Virginia Tidwell. At one of the SVP meetings in Denver, at a reception at the Denver museum, Virginia had invited me into the prep lab to see some EKNApod material from the Long Walk Quarry in Utah. The Long Walk Quarry was Frank DeCourten’s baby – he wrote a couple of papers about it (e.g., DeCourten 1991) and included additional information in his book, Dinosaurs of Utah (1998; second edition in 2013). DeCourten had referred the material to Pleurocoelus because that’s what people did with EKNApods back in the 20th century, but I remembered seeing one cervical that, like Sauroposeidon and YPM 5294, was just too long to match any of the Pleurocoelus material. My ‘Museum Photos’ file has a subfolder titled ‘Denver 2004’ – was the mystery vert in there?

2004-11-08 SVP 049

In short, yes. Here’s one of the photos I took back in 1994.

2004-11-08 SVP 050

Here’s another, sans flash this time. Check out the white spot on top of the condyle, the bar of float bone stuck sideways across the centrum just behind the spot, and general pattern of breaks – it’s a perfect match for UMNH 21054. Also note the block number on the pink specimen label at the bottom of the image – LWQ8, for Long Walk Quarry.

Three mysteries remain. One, the signage says the vert is from Carbon County, Utah, but the Long Walk Quarry has always been described as being in Emery County. Just a typo, or is there a story there? Two, how much of the animal (or animals) was excavated and prepped? I saw other vertebrae, both larger and smaller, when I was in Denver back on ’04, and DeCourten figured still others that I haven’t yet seen personally. Finally, is anyone working on it? And if not…[cautiously raises hand].

For other posts on the NHMU public galleries, see:

References

  • DeCourten, F.L.  1991.  New data on Early Cretaceous dinosaurs from the Long Walk Quarry and tracksite, Emery County, Utah.  In: T.C. Chidsey, Jr. (ed) Geology of East-Central Utah. Utah Geological Association Publication 19: 311-325.
  • DeCourten, F.L. 1998. Dinosaurs of Utah. University of Utah Press, Salt Lake City, 208pp.

A while back, we noted that seriously, Apatosaurus is just nuts, as proven by the illustrations in Ostrom and McIntosh (1966: plate 12).

Now I’m posting those illustrations again, in a modified form, to make the same point. Here ya go:

Brontosaurus excelsus holotype YPM 1980, cervical vertebra 8, in anterior, left lateral and ventral views. Adapted from Marsh's plates in Ostrom & McIntosh (1966).

Brontosaurus excelsus holotype YPM 1980, cervical vertebra 8, in anterior, left lateral and ventral views. Adapted from Marsh’s plates in Ostrom & McIntosh (1966: plates 12-13).

Here’s what’s changed since last time:

  1. Apatosaurusexcelsus is Brontosaurus again!
  2. I cleaned up the scans of the plates, removing all the labels
  3. In the lateral view, I added a reconstruction of the missing neural spine, based on that of Apatosaurus louisae (from Gilmore 1936: plate XXIV). This reconstruction first appeared in Taylor and Wedel (2013a: figure 7).
  4. Most importantly, I added the ventral view of the vertebra from plate 13. Only now can you properly appreciate the truly bizarre shape of this bone. (The prezygs appear to project further forward than they should because the illustrated aspect is not true ventral, but slightly anteroventral.)

If only those three views were enough to construct a 3D model by photogrammetry! Sadly, it’s not possible to get photos of the whole vertebra from different angles now, as it’s tied up in the mounted Brontosaurus skeleton at the YPM:

Part of the neck of the mounted skeleton of Brontosaurus excelsus holotype YPM 1980, in right posterodorsolateral view (i.e. from behind, above, and to the right). The vertebra in the centre of the picture may well be the one illustrated above, but don't hold me to it.

Part of the neck of the mounted skeleton of Brontosaurus excelsus holotype YPM 1980, in right posterodorsolateral view (i.e. from behind, above, and to the right). The vertebra in the centre of the picture may well be the one illustrated above, but don’t hold me to it.

The bottom line: these are some crazy-ass morphologically distinctive vertebrae. Those ventrolaterally projecting processes that bear the cervical ribs are, for my money, the single most distinctive feature of apatosaurine sauropods. And they reach their zenith (or maybe their nadir, since they point downwards) in Brontosaurus. These processes are the reason that apatosaurs had Toblerone-shaped necks — triangular in cross-section, with the base flat or even concave. Any restoration that shows a tubular neck is way off base.

References

AMNH 460 left anterolateral view

Apatosaurines on the brain right now.

I’ve been thinking about the question raised by Jerry Alpern, a volunteer tour guide at the AMNH, regarding the recent Tschopp et al. (2015) diplodocid phylogeny. Namely, if AMNH 460 is now an indeterminate apatosaurine, pending further study, what should the museum and its docents tell the public about it?

Geez, Apatosaurus, it’s not like we’re married!

I think it’s a genuinely hard problem because scientific and lay perspectives on facts and hypotheses often differ. If I say, “This animal is Apatosaurus“, that’s a fact if I’m talking about YPM 1860, the genoholotype of Apatosaurus ajax; it would continue to be a fact even if Apatosaurus was sunk into another genus (as Brontosaurus was for so long). We might call that specimen something else, but there would always be a footnote pointing out that it was still the holotype of A. ajax, even if the A. part was at least temporarily defunct – the scientific equivalent of a maiden name.* For every other specimen in the world, the statement, “This animal is Apatosaurus” is a hypothesis about relatedness, subject to further revision.

* This is going to sound kinda horrible, but when one partner in a marriage takes the other’s surname, that’s a nomenclatural hypothesis about the future of the relationship.

Apatosaurine cervicals are the best cervicals.

Apatosaurine cervicals are the best cervicals.

Fuzzy science

Things that look fairly solid and unchanging from a distance – specifically, from the perspective of the public – often (always?) turn out to be fairly fuzzy or even arbitrary upon closer inspection. Like what is Apatosaurus (beyond the holotype, I mean) – or indeed, what is a planet.** There is no absolute truth to quest for here, only categories and hypotheses that scientists have made up so that we can have constructive conversations about the crazy spectrum of possibilities that nature presents us. We try to ground those categories and hypotheses in evidence, but there will always be edge cases, and words will always break down if you push them too hard. Those of us who work on the ragged frontier of science tend to be fairly comfortable with these inescapable uncertainties, but I can understand why people might get frustrated when they just want to know what the damned dinosaur is called.

** Triton, the largest body orbiting Neptune, is almost certainly a captured Kuiper Belt object, and it’s bigger than Pluto. Moon or planet? Probably best to say a former dwarf planet currently operating as a satellite of Neptune – but that’s a mouthful (and a mindful, if you stop to think about it), not a short, convenient, easily-digestible label. Any short label is going to omit important information. This is related to the problem of paper title length – below some threshold, making something shorter means making it incomplete.

What I would say

I suppose the short version that is most faithful to the Tschopp et al. results is:

This skeleton (AMNH 460) might be Apatosaurus or Brontosaurus or a third, new thing – scientists aren’t sure yet.

A reasonable follow-up sentence – and an answer to the inevitable “Why not?” – would be:

They have to look at 477 anatomical details for lots of skeletons and weigh all the evidence, and that takes time.

Personally, if I was talking to museum visitors I would lean in conspiratorially and say:

If you want to call it Apatosaurus or Brontosaurus, go ahead – those are both ‘live’ hypotheses, and even the world’s experts on this problem can’t tell you that you’re guessing the wrong way – at least not yet.

And if there was a kid in the group, I’d add:

Maybe you’ll be the one to figure it out!

What would you say?

My neck is fat.

My neck is fat.

P.S. I wouldn’t change the signage. It could still turn out to be Apatosaurus, and the Tschopp et al. results do not lend themselves to easy label-ification.

P.P.S. With some modification for taxonomy, all of this applies to the Field Museum diplodocid FMNH P25112 as well.

Reference

Tschopp E, Mateus O, Benson RBJ. (2015) A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda) PeerJ3:e857 https://dx.doi.org/10.7717/peerj.857

Saurischian laminae and fossae v2 - Adam Marsh 2015

[Hi folks, Matt here. I’m just popping in to introduce this guest post by Adam Marsh (UT Austin page, LinkedIn, ResearchGate). Adam is a PhD student at UT Austin’s Jackson School of Geosciences, currently working for a semester as a Visiting Student Researcher at my old stomping ground, Berkeley’s UCMP.  Adam’s been working at Petrified Forest National Park in the summers and most of his research is on the Navajo Nation in Arizona. His major interest is in how we perceive extinctions in the fossil record. Specifically, he’s exploring the geochronology of the Glen Canyon Group to look at the biotic response to the end-Triassic mass extinction. He’s also working on an overhaul of the early saurischian dinosaurs of western North America – hence this post. It’s timely because I was just talking in the last post about putting together infographics to spread your ideas; here Adam’s very nice diagram serves as a quick guide and pointer to several papers by Jeff Wilson and colleagues. Many thanks to Sarah Werning for suggesting that Adam and I get acquainted over vertebrae. Update the next day: both the diagram above and the PDF linked below have been updated to fix a couple of typos. Also, there are now black and white versions – see below.]

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If you’re like me, you don’t count sheep when you fall asleep, you count laminae. These struts of bone and their affiliated fossae connect and span between major structural features on vertebral neural arches such as prezygapophyses, postzygapophyses, parapophyses, diapophyses, hyposphenes, hypantra, and the neural spine. Presumably, laminae bracket and fossae house outgrowths of pneumatic diverticula from the respiratory system, which has been covered extensively on this blog in sauropodomorph dinosaurs.

Talking about these complicated structures is cumbersome; they’ve been called buttresses, ridges, struts, etc. throughout descriptive skeletal literature. But what we call things is important, especially when we introduce laminae and other vertebral structures to the rigors of phylogenetic systematics, where homologous apomorphies reign supreme. In order to avoid arguing about whether one structure is called the potato or the tomato, Jeff Wilson and others introduced a strategy of naming vertebral laminae (Wilson, 1999) and the fossae (Wilson et al., 2011) that they surround using the same vertebral landmarks that most tetrapod anatomists agree upon (see the parade of –apophyses above). The process is very simple. Vertebral laminae are named for the two structures that they connect; the prezygodiapophyseal lamina (prdl) connects the prezygapophysis and the diapophysis, so each neural arch will have two prdls. Vertebral fossae are named for the two major laminae that constrain them; the prezygocentrodiapophyseal fossa (prcdf) opens anterolaterally and is delineated dorsally by the prezygodiapophyseal lamina and ventrally by the anterior centrodiapophyseal lamina. Again, each neural arch will have two prcdfs. Those of you who are black belt vertebral anatomists, to borrow a favorite phrase from my advisor, might be interested in serial variation and how these structures change up and down the vertebral column. Until I get my act together and publish some cool new saurischian data, I will refer you to Wilson (2012). [We’ve also touched on serial variation in laminae in this post and this one. – MJW]

Saurischian laminae and fossae v2 bw - Adam Marsh 2015

Same thing in black and white, with labels

 

You might have noticed that the names are a mouthful and take up their fair share of typed characters. In my research of early saurischian dinosaurs, I’ve run across quite a few of these laminae everywhere from herrerasaurids to sauropodomorphs to coelophysoids to Dilophosaurus. Even though I’ve drawn, photographed, and written about various laminae and fossae, I still need to remind myself of what goes where and what it’s called. Believe me, vertebral lamina nomenclature does not lend itself well to Dem Bones covers. As a result, I’ve put together a reference figure that might be useful for those of you who are dealing with this or even teaching it to students. At the very least, you can put it on the ceiling above your bed so that it’s the first thing you see when you open your eyes in the morning.

Four main vertebral laminae are present plesiomorphically in archosaurs: the anterior and posterior centrodiapophyseal laminae, the prezygodiapophyseal lamina, and the postzygodiapophyseal lamina. This means that the prezygocentrodiapophyseal, postzygocentrodiapophyseal, and centrodiapophyseal fossae are present, and sometimes the top of the transverse process is concave between the neural spine and the zygapophyses to form the spinodiapophyseal fossa. I know that a certain sister group of Sauropodomorpha can get disparaged around these parts, but the truth is that theropods build long necks, too, and sometimes in very different ways than sauropodomorphs. When you are writing about the various vertebral buttresses and chonoses, don’t get frustrated with the names, because Wilson and his colleagues have actually made it much easier for us to talk to one another about presumably homologous structures without needing an additional degree in civil engineering.

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Here’s the figure again in PDF form: Marsh, Adam 2015 saurischian laminae and fossae diagram v2

And in black and white for those who prefer it that way: Marsh, Adam 2015 saurischian laminae and fossae diagram v2 bw

References

According to Rare Historical Photos from the 1860s to the 1960s, this is the iceberg that sank the Titanic:

 photo of the iceberg that sunk the Titanic, taken the morning of April 15, 1912 from board of the ship “Prinz Adalbert”, before knowing the Titanic had sunk. The smear of red paint along the base of the berg (bottom right) prompted the chief steward to take the picture.

photo of the iceberg that sunk the Titanic, taken the morning of April 15, 1912 from board of the ship “Prinz Adalbert”, before knowing the Titanic had sunk. The smear of red paint along the base of the berg (bottom right) prompted the chief steward to take the picture.

Clearly this was no iceberg, but a gigantic Apatosaurus vertebra, most of it hidden under water. Here is an artist’s impression:

iceberg

They get everywhere, don’t they?

Having given pterosaurs all the glory in two earlier posts, it’s time to move yet further away from the sauropods we know and love, and look at epipophyses outside of Ornithodira.

Here, for example, is the basal archosauriform Vancleavea. (Thanks to Mickey Mortimer, whose a comment on an earlier post put us onto this, and various other candidate epipohysis-bearers which we’ll see below.)

Here is a pair of Vancleavea cervical vertebrae:

Nesbitt et al. (2009: fig. 11A). Vertebrae of Vancleavea campi. Two articulated cervical vertebrae (PEFO 33978) in left lateral view.

Nesbitt et al. (2009: fig. 11A). Vertebrae of Vancleavea campi. Two articulated cervical vertebrae (PEFO 33978) in left lateral view.

No ambiguity here: the epipophysis is even labelled.

But we can find epipophyses even outside Archosauriformes. Here, for example, is the the rhynchosaur Mesosuchus:

Dilkes (1998: fig. 7A). Mesosuchus browni. Holotype SAM 5882. Partial skull and jaws and cervical vertebrae in left lateral view.

Dilkes (1998: fig. 7A). Mesosuchus browni. Holotype SAM 5882. Partial skull and jaws and cervical vertebrae in left lateral view.

Check out the rightmost vertebra (C7), clicking through for the full resolution if necessary. There is a definite eminence above the postzyg, separated from it by a distinct groove. Unless the drawing is wildly misleading, that is a definite epipophysis, right there.

But even more basal archosauromorphs have epipophyses. Check out Teraterpeton, described by Hans-Dieter Sues in 2003:

Sues (2003: figure 7). Teraterpeton hrynewichorum, NSM 999GF041 (holotype), cervical and anterior dorsal vertebrae and ribs, associated with right scapula (sc), ?clavicles (cl?), ?interclavicale (ic?), and incomplete right humerus (h), in right lateral view. Scale bar = 1 cm. a.p., accessory process above postzygapophysis; ax, axis; c3, c4, cervical vertebra 3 and 4, respectively; t, displaced tooth.

Sues (2003: figure 7). Teraterpeton hrynewichorum, NSM 999GF041 (holotype), cervical and anterior dorsal vertebrae and ribs, associated with right scapula (sc), ?clavicles (cl?), ?interclavicale (ic?), and incomplete right humerus (h), in right lateral view. Scale bar = 1 cm. a.p., accessory process above postzygapophysis; ax, axis; c3, c4, cervical vertebra 3 and 4, respectively; t, displaced tooth.

This is another one where the epipophysis is labelled (though not recognised as such — it’s just designated an “accessory process”).

Can we go yet more basal? Yes we can! Here are cervicals 2 and 3 of the trilophosaur Trilophosaurus (in an image that I rearranged and rescaled from the published original for clarity):

Spielmann et al. (2008: figure 30, rearranged). Cervical vertebrae 2-3 (i.e. axis and C3) of Trilophosaurus buettneri TMM 31025-140. Top row: right lateral. Second row: dorsal, with anterior to the left. Third row, left to right: anterior, left lateral, posterior. Bottom row: ventral, with anterior to the left.

Spielmann et al. (2008: figure 30, rearranged). Cervical vertebrae 2-3 (i.e. axis and C3) of Trilophosaurus buettneri TMM 31025-140. Top row: right lateral. Second row: dorsal, with anterior to the left. Third row, left to right: anterior, left lateral, posterior. Bottom row: ventral, with anterior to the left.

The parts of this image to focus on (and you can click through for a much better resolution) are the postzyg at top right of the left-lateral view, which has a distinct groove separating the zygapophyseal facet below from the epipohysis above; and the posterior view, which also shows clear separation on both sides between these two structures.

While we’re playing with trilophosaurs here’s here’s another one (probably), Spinosuchus:

Spielmann et al. (2009: figure 3N). Spinosuchus caseanus holotype UMMP 7507, 5th cervical vertebra in left lateral view.

Spielmann et al. (2009: figure 3N). Spinosuchus caseanus holotype UMMP 7507, 5th cervical vertebra in left lateral view.

Again, the groove separating postzygapophyseal facet from epipophysis (at top right in the image) is clear.

But there’s more! Even the protorosaurs, pretty much the most basal of all archosauromorphs, have convincing epipophyses. Here are two that I found in Dave Peters’ post from two years ago, which I only discovered recently. [Here I must insert the obligatory disclaimer: while Dave Peters is a fine artist and has put together a really useful website, his ideas about pterosaur origins are, to put it mildly, extremely heterodox, and nothing that he says about phylogeny on that site should be taken as gospel. See Darren’s write-up on Tet Zoo for more details.]

Dave shows some probable, but not super-convincing epipophyses in the protorosaur Macrocnemus (shaded purple here) …

Cervicals 1-6 of the protorosaur Macrocnemus, modified from an uncredited image on Dave Peters' site. Postzygapophyses in yellow, epipophyses in purple.

Cervicals 1-6 of the protorosaur Macrocnemus, modified from an uncredited image on Dave Peters’ site. Postzygapophyses in yellow, epipophyses in purple.

… and some much more convincing epipophyses in the better known and more spectacular protorosaur Tanystropheus:

Unspecified single cervical of Tanystropheus, from Dave Peters' site. Postzygapophysis in yellow, epipohysis in purple.

Unspecified single cervical of Tanystropheus, from Dave Peters’ site. Postzygapophysis in yellow, epipohysis in purple.

Frustratingly, Dave doesn’t attribute these images, so I don’t know where they’re originally from (unless they’re his own artwork). Can anyone enlighten me? There’s a nice illustration in figure 57 of Nosotti’s (2007) epic Tanystropheus monograph that is at least highly suggestive of epipophyses:

Nosotti (2007:figure 57). Reconstruction of an anterior cervical vertebra (A) and of a mid-cervical vertebra (B) in small-sized specimens of Tanystropheus longobardicus. Left lateral view. Not to scale. Watercolor: Massimo Demma. Abbreviation pzp = postzygapophyseal process.

Nosotti (2007:figure 57). Reconstruction of an anterior cervical vertebra (A) and of a mid-cervical vertebra (B) in small-sized specimens of Tanystropheus longobardicus. Left lateral view. Not to scale. Watercolor: Massimo Demma. Abbreviation pzp = postzygapophyseal process.

But it’s not as good as the one Peters used, as that one shows a distinct notch between postzyg and epipophysis, so I’d like to track that down if I can.

With this, I believe I am done on cataloguing and illustrating epipophyses, unless something dramatic turns up. (For example, this commenter thinks that nothosaurs have epipophyses, but I’ve not been able to verify that.) Here’s what we’ve found — noting that we’ve illustrated epipophyses on every taxon on this tree except Crocodylia:

tree

So it seems that epipophyses may well be primitive at least for Archosauromorpha — which implies that they were secondarily lost somewhere on the line to modern crocs.

With this lengthy multi-part digression complete, hopefully, we’ll get back to sauropods next time!

References

  • Dilkes, David W. 1998. The Early Triassic rhynchosaur Mesosuchus browni and the interrelationships of basal archosauromorph reptiles. Philosophical Transactions of the Royal Society of London B 353:501-541.
  • Kellner, Alexander W. A., and Yukimitsu Tomida. 2000. Description of a new species of Anhangueridae (Pterodactyloidea) with comments on the pterosaur fauna from the Santana Formation (Aptian-Albian), Northeastern Brazil. National Science Museum monographs, Tokyo, 17. 135 pages.
  • Nesbitt, Sterling J., Michelle R. Stocker, Bryan J. Small and Alex Downs. 2009. The osteology and relationships of Vancleavea campi (Reptilia: Archosauriformes). Zoological Journal of the Linnean Society 157:814-­864.
  • Nosotti, Stefania. 2007. Tanystropheus longobardicus (Reptilia, Protorosauria): re-interpretations of the anatomy based on new specimens from the Middle Triassic of Besano (Lombardy, Northern Italy). Memorie della Societa Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano 35(III). 88pp.
  • Spielmann, Justin A., Spencer G. Lucas, Larry F. Rinehart and Andrew B. Heckert. 2008. The Late Triassic Archosauromorph Trilophosaurus. New Mexico Museum of Natural History and Science Bulletin 43.
  • Justin A. Spielmann, Spencer G. Lucas, Andrew B. Heckert, Larry F. Rinehart and H. Robin Richards III. 2009. Redescription of Spinosuchus caseanus (Archosauromorpha: Trilophosauridae) from the Upper Triassic of North America. Palaeodiversity 2:283-313.
  • Sues, Hans-Dieter. 2003. An unusual new archosauromorph reptile from the Upper Triassic Wolfville Formation of Nova Scotia. Canadian Journal of Earth Science 40:635-649.

This just in, from Zurriaguz and Powell’s (2015) hot-off-the-press paper describing the morphology and pneumatic features of the presacral column of the derived titanosaur Saltasaurus. (Thanks to Darren for bringing this paper to my attention.)

Now, as everyone knows, titanosaurs don’t have epipophyses. In fact, they’re the one major sauropod group where Matt has not observed them.

Until today.

Zurriaguz and Powell (2015:figure 3B). Anterior cervical vertebra PVL 4017-3 of Saltasaurus loricatus, in dorsal view (rotated 90° from the paper)

Zurriaguz and Powell (2015:figure 3B). Anterior cervical vertebra PVL 4017-3 of Saltasaurus loricatus, in dorsal view (rotated 90° from the paper)

Look at the left postzygapophysis, at top left of this image. Doesn’t that look like there’s a distinct rounded eminence sticking out towards the camera?

No? Not convinced? All right, then, how about this?

Zurriaguz and Powell (2015:figure 4B). Mid-anterior cervical PVL 4017-138 of Saltasaurus loricatus in right lateral view.

Zurriaguz and Powell (2015:figure 4B). Mid-anterior cervical PVL 4017-138 of Saltasaurus loricatus in right lateral view.

This time, look at the right postzyg (again at top left in the image). Doesn’t that look like there are two separate bony structures up there separated by a notch? A postzygapophyseal facet below, and an epipophysis above? Right?

Huh? What’s that? Just damage, you say?

All right. Let’s bring out the smoking gun.

Zurriaguz and Powell (2015:figure 5). Last anterior cervical vertebra (PVL 4017-5) of Saltasaurus loricatus in right lateral view. (Ignore the inset square for our purposes: it's in the original.)

Zurriaguz and Powell (2015:figure 5). Last anterior cervical vertebra (PVL 4017-5) of Saltasaurus loricatus in right lateral view. (Ignore the inset square for our purposes: it’s in the original.)

Again up at top left, we seem to have a clear case of a ventrally directed postzygapophyseal facet surmounted by a separate eminence which can only be an epipophysis. It even seems to be roughened for tendon attachment.

What does this mean? Only the same thing we said last time: The more we look for epipophyses, the more we find them. Amazing how often that turns out to be true of various things.

We seem to be headed towards the conclusion that epipophyses, while never ubiquitous, pop up in all sorts of places scattered all across the ornithodiran tree, encompassing birds, other theropods, sauropods, prosauropods, several groups of ornithischians, and both pterodactyloid and “rhamphorhynchoid” pterosaurs.

But what about outside Ornithodira?

Can we find epipophyses even out there, in the wilderness?

Stay tuned!

References

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