Can it be? Even more non-dinosaurian epipophyses? Yes, and this time they’re non-ornithodiran!
February 8, 2015
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.
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.
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.
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.
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.
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.
… 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.
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.
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:
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.
Sauropod Vertebra Picture of the Week 
February 8, 2015 at 4:55 pm
Mike, I think the Tany vert is from Wild’s treatise. Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus (Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-16. Sorry I overlooked the attribution. My bad.
To your point on pterosaur origins, yes, heterodox (= different), but that’s not a bad thing as many dead scientists of the past know who have been later vindicated.
Odd that in your tree pterosaurs nest between Vancleavea + crocs and ornithischia + theropods. I can’t see any obvious shared ptero traits there. If you’re looking for them, the latest large reptile tree, now closing in on 500 taxa, is at http://www.reptileevolution.com/reptile-tree.htm, has a long list of pterosaur ancestors going back to Pederpes. Remove one headless/head only taxon pairing and it remains fully resolved.
Dave
February 8, 2015 at 5:03 pm
Hi, Dave, thanks for dropping in and for the attribution of the Tany vert.
On heterodoxy: I’m not qualified to judge the strength or weakness of your hypothesis, which is why I described it only as “heterodox” rather then “wrong” or “falsified” or something else stronger. I just want SV-POW! readers to understand that what they read on your site doesn’t correspond with the general consensus. On that basis, they can make up their own minds.
Yep. I’m just following the consensus of researchers who work in that part of the tree. It’s no part of what we’re writing here to reevaluate the phylogeny. We’re just using it as a framework for our anatomical observations and mechanical speculations.
No doubt people who know basal archosauromorphs better than I do will chip in.
February 9, 2015 at 3:51 am
Mike, I’m assuming your cladogram illustrates taxa with epipophyses, but it misses a (?) mamenchisaurid. Omeisaurus seems to have them as well, as you can tell in one of your own images: https://svpow.files.wordpress.com/2012/09/fig8-neurapophyseal-spurs.jpeg
February 9, 2015 at 4:26 am
In addition, I might have narrowed down where on the crocodilian line epipophyses disappeared. Look at this figure of Baurusuchus: http://www.scielo.br/scielo.php?pid=S0031-10492010002100001&script=sci_arttext#fig2 It labels the postzygapophyses, and even though the notch isn’t very obvious, it at least it slightly visible. Is this an example of a true crocodile line epipophyses?
February 9, 2015 at 7:46 am
Hi, ijreid, thanks for this. I omitted Omeisaurus deliberately, because I’m not quite convinced by the evidence. It’s based on a rather idealised sketch of, which doesn’t show epipophyses clearly, of a single bone which has since been lost. (Aside: how do you lose a sauropod vertebra? Seriously.) In all probability, Omeisaurus did have them, but I didn’t find the evidence compelling.
I’m not seeing epipohyses in that Barasuchus figure.
February 9, 2015 at 10:36 am
This quote from Nesbitt (2011: p. 109) might be of interest:
“Langer and Benton (2006) state that epipophyses are present in non-dinosaurian archosaurs such as Batrachotomus. In fact, they are more common among basal archosauriforms than discussed by Langer and Benton (2006). Epipophyses are present in Batrachotomus (Langer and Benton, 2006; Gower and Schoch, 2009), Revueltosaurus (Parker et al., in prep.), Vancleavea (PEFO 33978), Mesosuchus (SAM8552), Xilousuchus (IVPP V 6026), and on the atlantal neural arch of Effigia (AMNH FR 30587; Nesbitt, 2007) and Hesperosuchus (AMNH FR 6758).”
February 9, 2015 at 10:40 am
Thanks, Mark, very helpful.
February 10, 2015 at 4:18 pm
Bingo! Check this out:
http://dipbsf.uninsubria.it/paleo/nothosaurus.htm
Look at the vertebra illustration. you can clearly make out epiphyses in figures E and F!
February 10, 2015 at 4:22 pm
Or at least those projections look like epipophyses, especially in figure E!
February 10, 2015 at 4:28 pm
You can also view the epipophyses of Nothosaurus
here: http://upload.wikimedia.org/wikipedia/commons/2/21/Skeleton_Nothosauria_naturkundemuseum_Berlin.jpg
February 10, 2015 at 4:31 pm
Better still, http://dipbsf.uninsubria.it/paleo/renestoRIPS2010.pdf is the paper itself, so I can see the proper captions. (The ones in the page you linked are not so great — for example, they don’t even mention parts F-H of the vertebra figure, and have some of the aspects wrong.)
I’m afraid, though, that I don’t find it at all convincing as evidence for epipophyses. The text doesn’t mention them at all; fig. 5E is a caudal central while epipophyses are found above cervical postzygapophyses; and fig. 5F is again from a caudal. It’s a neural arch in lateral view, but so poorly rendered that I can’t even tell which way it’s oriented.
Am I missing something? Perhaps you could post an annotated version of the figure, highlighting the parts that you think are epipohyses?
February 10, 2015 at 4:33 pm
Hmm. I didn’t see anything at that first link that looked like an epipophysis. It’s not enough for there to be a projection–the projection must be clearly separate from the postzygapophysis. In F, I think the two things sticking out to the left are the transverse process and the postzyg, not the postzyg and the epipophysis. But I’m open to being corrected by someone who knows the critter better.
The Wikimedia image is more tantalizing, but the resolution is too low for me to be certain. Does anyone have a higher-res shot?
February 10, 2015 at 4:35 pm
I’m afraid that photo of the Berlin skeleton is not high enough resolution for me to be able to make out convincing epipophysis, nor to tell whether the cervicals are real. (I did look closely at that photo previously when I was trying to find evidence for nothosaur epipophyses, and also at my own photo of the same exhibit. No luck.)
February 10, 2015 at 4:58 pm
This just in from Museum für Naturkunde Postdoctoral Researcher Christian Kammerer:
So we’ll need to look elsewhere for evidence of nothosaur epipophyses.
February 10, 2015 at 10:27 pm
Yes It seems we do. I realize now that my not so detailed iPhone screen distorted the image a bit and made it seem like there were protrusions distinct from the postzygapophyses, but now, having reviewed the images, I don’t see anything. As for Nothosaurs in general, I’m going to do a bit of research on their vertebrae to (hopefully) find some epipophyses, but that research will have to wait until I finish working on an exhibit for the Stamford Museum. Anyways, great post and a great conclusion to a fascinating series Mike!
February 11, 2015 at 11:41 am
The news on nothosaur epipohyses is not good:
(From Christian Kammerer.)
February 11, 2015 at 4:08 pm
Okay, this sauropod is for certain. Yunmenglong. Once I got my ScienceDirect access, I came across the original description, and figure 2, the vertebrae, even label the epipophyses. If you like, I can email you the figure, but I cannot link to it unless you have access as well.
February 11, 2015 at 4:19 pm
Yep, Yunmenglong is good: Lü et al. (2013:fig. 2A-C) is pretty convincing.