Tutorial 4b: Saurischian vertebral laminae and fossae redux, by Adam Marsh

April 17, 2015

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


20 Responses to “Tutorial 4b: Saurischian vertebral laminae and fossae redux, by Adam Marsh”

  1. Bill Parker Says:

    All archosauromorph workers need this sheet.

  2. Mike Taylor Says:

    Nice work! I spotted a couple of mistakes, though: the centropostzygapophyseal lamina is abbreviated COPL rather than CPOL; and the TPRL and TPOL are notated as “infra-” rather than “intra-“.

    Also, if a revision is in the works, it would be good to bring the parapophysis in.

  3. Mike Taylor Says:

    Oh, found a mistake in the text, too: “the truth is that theropods build long necks, too”.



  4. Great illustration, but is there a color-blind version? This may simplify things for some, but not for others.

  5. Mike Taylor Says:

    Jaime, how could a colour-blind version be made? I can’t see how it could be managed.

  6. Serjoscha Evers Says:

    Just out of interest: Do you SVPOW guys advocate the use of the term “pleurocoel”? I try to avoid it, and use, in case of a true foramen (i.e. connecting to an internal chamber of the centrum), the term central pneumatic foramen/foramina, depending on whether one or more exist.

  7. Mike Taylor Says:

    Our position on “pleurocoel” is found in Taylor and Naish (2007:1548) (the Xenoposeidon paper):

    Anatomical nomenclature. The term “pleurocoel” has been widely used to refer to the lateral excavations in the centra of sauropods and other saurischian dinosaurs. However, the blanket use of this term obscures the morphological diversity of these cavities, which varies considerably between taxa, encompassing everything from broad, shallow fossae to small, deep foramina; and some taxa have both of these. Furthermore, the term has been used inconsistently in the literature, so that characters such as “pleurocoels present” in cladistic analyses are difficult to interpret. For example, in the analysis of Wilson (2002), character 78 is defined as “Presacral centra, pneumatopores (pleurocoels): absent (0); present (1)” (Wilson 2002, p. 261), and Barapasaurus Jain, Kutty and Roy-Chowdhury, 1975 is scored as 0 (“pleurocoels absent”). While Barapasaurus does indeed lack pneumatic foramina, it has shallow lateral fossae (Jain et al. 1979, pls 101-102), a feature that is not conveyed by the traditional terminology. Accordingly, we recommend that the ambiguous term “pleurocoel” (and Wilson”s equivalent “pneumatopore”) be deprecated in favour of the more explicit alternatives “lateral fossa” and “lateral foramen” (Britt 1993, 1997; Wedel et al. 2000b; Wedel 2003, 2005).

  8. Mike: a colo(u)r-blind version might be doable using different patterned stipples for shades, and different weights/dashes for line.

  9. David Marjanović Says:


  10. Adam Marsh Says:

    Thanks, Mike. I’ll correct the typos and provide the revison

  11. Bill Parker Says:

    Photoshop includes a test to display how your graphic looks under the different types of color “blindness”. It is a great tool. In CS 6 it is under View>Proof Setup.

  12. Adam Marsh Says:

    The revised figure is in to Matt, I’m sure he’ll post it when he’s able. I’ll let an intrepid lamina enthusiast modify it by bringing the parapophysis up onto the neural spine. In terms of a color-blindness safe version, Dr. Holtz’s suggestion could work. If anyone wants an Illustrator or Gimp file to modify this in any way they see fit, feel free to email me and I’d be happy to send one along.

  13. Adam Marsh Says:

    My apologies for the errors. Those are exactly the kinds that sneak in after staring at these for a long time

  14. Matt Wedel Says:

    The updated PNG (top) and PDF (bottom) are now up. Thanks, Adam, for the quick revisions.

  15. Matt Wedel Says:

    …and now there are black and white versions for people who are colorblind, don’t have access to color printers, or just prefer it that way.

  16. Tom Johnson Says:

    This is great. It is very helpful for a non-professional to decipher some of the characters in Tschopp et al. Thanks!

  17. This is now on my office corkboard–I hope to learn these names by osmosis over time.

  18. Mark Robinson Says:

    Good stuff. My colour vision is normal and I usually find that colour-coding data greatly helps my understanding of charts or even lists – I said before that the sauropod vertebrae bifurcation “heat map” was a stunning piece of work and a personal favourite.

    However, with the above info-graphics, I found that the black and white version enabled me to get my head around the data both more easily and more quickly than the coloured original. I think that the labels pointing explicitly to the things that they are referencing is a big part of this but also, some of the colours (eg those for ‘acdl’ and ‘cprl’) are too similar to each other which meant having to lean closer to my monitor to be sure of what I was looking at.

    Perhaps a single info-graphic with colour and labels would better meet different people’s requirements? I wouldn’t be surprised if working out how best to convey data is a whole area of study itself.

  19. […] indet. (DGM 929-R)36. (K,L) Ibirania parva (LPP-PV-0200)37. (M,N) Dilophosaurus wetherilli38. Lateral view in (A,C,F,I,L,N). Transverse sections in (B,D,E,J,K,M). Ventral view in (G). High […]

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