Further exciting developments in the field of non-sauropod epipophyses

February 4, 2015

Many thanks for the various people who chipped in, both in comments on the last post and in this thread on twitter, where I asked a bunch of pterosaur experts for their thoughts on epipophyses in pterosaurs. I now know more than I previously knew about epipophyses outside of Sauropoda — and especially outside Dinosauria. I’ll try to credit everyone who contributed.

Occasional SV-POW!sketeer Darren Naish claims that according to the literature, ornithischians lack epipophyses — something that we’ve seen is untrue. I never got references out of him, though. Can anyone point me to the guilty literature?

Darren also gave me the rather cryptic instruction “Look at Anhanguera monographs. Sorry, can’t check myself.” Like something from a spy novel. Checking out Kellner and Tomida (2000), I found their illustration of the Anhanguera atlas/axis complex, in figure 14B, suggestive:


It took me a while to figure this out, but I think this is showing the first three cervicals, not two: the atlas is tiny, and is smushed onto the front of the axis; C3 is shown, but only in outline, and is ignored in the caption.

As labelled, the postzygapophyseal facet of the axis is tiny — and there’s a definite protuberance above it, which can only be an epipophysis. But we’d need photos to be confident. The good news is that there is a photo in the paper — part A of the same figure. But the bad news is that here’s how it looks in my scan:


Not so helpful. If anyone has a good scan — or better still an original photo — I’d like to see it.

Darren also commented “Most big pterosaurs lack epipophyses. Ornithocheirids may be the exception”, but there his hints dried up. Mark Witton cautioned me: “Not sure for azhdarchids. Well preserved verts have reduced features, but not entirely absent as badly preserved verts suggest.” So perhaps the Phosphatodrado vertebrae in the last post are not so compelling as they seem.

Liz Martin suggested “off the top of my head you could check Wellnhofer papers. 1991 and 1985 I think show verts.” But I couldn’t find any vertebrae in the only Wellnhofer (1985) that I have; and there are at least three Wellnhofer publications from 1991, which I’ve not checked yet. Any more guidance, anyone?

So how widespread are epipohyses? Brusatte et al. (2010:73) gave “Epipophyses on the cervical vertebrae” as a synapomorphy diagnosing Dinosauria: Epipophyses on the cervical vertebrae. Epipophyses are projections of bone, likely for muscle and ligament attachment, which protrude from the dorsal surfaces of the postzygapophyses of the cervical vertebrae. All basal dinosaurs possess epipophyses (Langer and Benton, 2006), although the size, shape, length, and projection angle of these processes vary considerably (e.g., compare Coelophysis (Colbert, 1989) with the more derived theropod Majungasaurus (O’Connor, 2007)). Basal ornithischians (e.g., Heterodontosaurus) only have epipophyses on the anterior cervical vertebrae, whereas saurischians have epipophyses in nearly all cervical vertebrae (Langer and Benton, 2006). Epipophyses are not present in the closest relatives of dinosaurs (e.g., Marasuchus, Silesaurus), but are present in some crurotarsans (e.g., Lotosaurus and Revueltosaurus).

It’s surprising that they’d mention dinosaurs and croc-line archosaurs, but overlook pterosaurs, which are phylogenetically bracketed by that group. But there’s lots of useful detail to follow up in the citations, which I’ll be doing soon.

So: moving down the tree from Sauropoda, we see epipophyses:

  • often but not always in sauropods
  • rarely in basal sauropodomorphs
  • often, maybe always, in theropods
  • intermittently but not infrequently in ornithischians
  • in at least some basal dinosauriforms
  • in some groups of pterosaurs but not others
  • in at least some croc-line archosaurs — but not, for example, in alligators.

Does anyone know of epipophyses outside Archosauria?

We seem now to be stumbling towards a conclusion of sorts, which is that epipophyses seem to be rather phylogenetically labile, coming and going within numerous lineages. As with so many vertebral features, they also vary with serial position, which complicates matters; and, I dare guess, with ontogeny.

I’ve not been able to locate any publications that are specifically about epipophyses (just lots that mention them in passing). Does anyone know of such a thing?


9 Responses to “Further exciting developments in the field of non-sauropod epipophyses”

  1. Mickey Mortimer Says:

    “Darren Naish claims that according to the literature, ornithischians lack epipophyses”

    Classically yes. Gauthier (1986) regarded them as a saurischian character for instance, but by the time of Sereno and Novas (1993) at least they were recognized in some ornithischians.

    “Does anyone know of epipophyses outside Archosauria?”

    Trilophosaurus (Spielmann et al., 2008), Spinosuchus (Spielmann et al., 2009), Teraterpeton (Sues, 2003), Mesosuchus (Dilkes, 1998), Vancleavea (Nesbitt et al., 2009)… There are probably more, but authors describing these taxa don’t seem familiar with the concept.

  2. Anonymous Says:

    Typing in “ornithischian” and “epipophyses” in Google Scholar brings up a ton of papers for heterodontosaurids and other basal ornithischians, for some reason. Can’t get access to papers because traveling, but it looks like epipophyses may be common in these taxa.

  3. As noted above Vancleavea. And I have a hunch about nothosaurs having them.

  4. It seems nothosaurs do in some cases but the epiphyses are very reduced. What’s hard about looking for them in nothosaurs is that I can’t seem to find good high-quality pictures of actual skeletons.

  5. Mike Taylor Says:

    It’s true: the Internet is woefully low on high-quality photos of vertebrae from almost all taxa, with sauropods being an honourable exception. It’s amazing — both gratifying and frustration — how often, when I search for images of any kind of vertebra, a whole bunch of SV-POW! stuff comes up.

    Come on, advocates of other taxa! Get your Taxon Vertebra Picture of the Week blogs up and running!

  6. Adam Says:

    I can say from first hand examination of many taxa involved that epipophyses are ubiquitous among basal sauropodomorphs, definately not rare at all. What does vary is if they are overhanging, finger-like epipophyses (e.g. Plateosaurus), more flattened, plate-like overhanging epipophyses (Pantydraco? and at least one referred vertebra of Thecodontosaurus) or non-overhanging boss-like structures sitting above the postzygapophyses (Massospondylus, Melanorosaurus, Aardonyx, Riojasaurus, ‘Yunnanosaurus’ robustus, Plateosauravus, Jingshanosaurus amongst others). These epis stretch from the axis to the base of the neck, although the last few can be quite subdued. My take is that postaxial epis were present in the ancestral saurischian and were kept by most lineages although some Sauropods lost them.

  7. Mike Taylor Says:

    Thanks, Adam, really helpful. (Good to hear from you, by the way!)

  8. […] various complicated reasons it’s yet to be published. But as part of our ongoing quest for pterosaur epipophyses, I have obtained these photos of a pretty well preserved single cervical, probably C3, which is […]

  9. […] 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 […]

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