The world’s best Tenontosaurus skull

August 19, 2015

Thomas 2015 figure 2

Left lateral skull schematic (above) and left skull photograph (below) of OMNH 58340. The skull is angled at the ‘alert position’ indicated by the horizontal semicircular canal. Natural fenestrae are shaded gray. Dashed outline denotes conjectural sclerotic ring. Anterior is to the left. Abbreviation: mf – maxillary foramen. Thomas (2015: fig. 2).

As stinkin’ ornithischians go, Tenontosaurus is near and dear to my heart. For some reason beyond the ken of mortals, the Antlers Formation of southeast Oklahoma has yielded only a small handful of Acrocanthosaurus (Stovall and Langston 1950; Currie and Carpenter 2000), one partial Deinonychus skeleton and a few dozen shed teeth (Brinkman et al. 1998), the single, lonely, woefully incomplete holotype specimen of Sauroposeidon (Wedel et al. 2000a, b) – and roughly five flarkjillion skeletons of Tenontosaurus. I know a lot of those skeletons intimately: between 1994 and 2001, I went on about two dozen OMNH digs to pull them out of the ground, and I worked on a couple as a volunteer preparator.

Thomas 2015 figure 18

Anterior skull schematic (above) and photograph (below) of OMNH 58340. The two images are set to the same scale, demonstrating the amount of displacement in the right side of the skull. The schematic was reconstructed by digitally mirroring the left side of the rostrum and suspensorium in order to approximate the actual appearance of the skull. Natural fenestrae are shaded gray. Anterior is out of the page. Thomas (2015: fig. 18).

I was off to Berkeley in 2001, so I missed the fun when another crew got the best-ever Tonto specimen, OMNH 58340. Except for the back half of the tail, which had eroded away, almost every bit of the skeleton was preserved in perfect articulation, even the hyoid apparatus, terminal phalanges, proatlas, and atlas cervical ribs. The skull was a bit disarticulated – half of the rostrum had floated out of position, and the stapes and palpebrals were missing – but it’s still the nicest Tonto skull ever found, and one of the best-preserved fossils to ever come out of the Antlers Formation.

Now that skull has been very thoroughly described by Andrew Thomas. Andrew wrote it up for his MS thesis under my first mentor, Rich Cifelli, and it was published last month in Palaeontologica Electronica (Thomas 2015). I had dinner with Andrew and his family when I visited the OMNH in the spring of 2014, and he showed me a down-scaled translucent 3D print of the left half of OMNH 58340. I learned more about ornithischian skulls playing with that thing over dinner than I had in the previous two decades of (admittedly quarter-assed) study.

Thomas 2015 figure 10

Medial view of the left side of the virtual skull of OMNH 58340 with the vomer present (10.1), allowing a view of the articulation of the vomer with the pterygoid, and with the palatine and vomer removed (10.2), allowing a view of the joints between the maxilla, lacrimal, prefrontal, jugal, ectopterygoid, and pterygoid. The vertically striated texture present on the visible surfaces of many elements, notably the lacrimal, maxilla, and premaxilla, is an artifact of the process used to isolate CT images of each element from the remainder of the data set. Abbreviations: f – flange; pp – posterior processes; tp – triangular processes. Thomas (2015: fig. 10).

So there’s me, playing with a down-scaled 3D print of a Tonto skull. Why am I telling you about this? Because if you want to print your own, you can – digital models of the complete cranium, and all of the individual elements, are available as STL files published along with the paper. Getting to the models takes some doing – they’re in a ZIP file linked from the paper’s Appendix 4, which you can access directly here.

Thomas (2015) has a lot more than just cool 3D models – there’s a lot of descriptive goodness, including the cranial endocast, cranial nerves, inner ear labyrinth, and hyoids; a whopping 62 figures, most in full color; and a phylogenetic analysis that incorporates the new morphological data on Tenontosaurus. No revelations there – despite all the nice specimens, Tonto remains an enigma from the murky realm between basal ornithopods and Iguanodontia. But if Oklahoma’s most abundant dinosaur is a bit of a phylogenetic mystery, it’s also becoming a paleobiologic gold mine, thanks in large part to the bone histology studies of Sarah Werning and colleagues (Lee and Werning 2008; Werning 2012 – also see Horner et al. 2009 on histology of Tenontosaurus from the Cloverly Formation of Montana). With the publication of this paper, Andrew Thomas is now part of the “Tenontaissance”. Congratulations, Andrew, and well done!

Now if we could just get some more Sauroposeidon



18 Responses to “The world’s best Tenontosaurus skull”

  1. Mike Taylor Says:

    Dude, it’s time you faced the fact that you have a serious problem. It’s always the same with ornithischian skull addicts, they’re all “I can give it up any time I want”. But you’re fooling yourself. If this goes on much longer, I’m gonna have to get together with Darren and stage an intervention.

  2. Mike Taylor Says:

    That aside … truly beautiful descriptive work, showing again just how far the online-only open-access journals have raised the bar for this kind of thing. This must have been one heck of an MS thesis.

  3. Andrew Thomas Says:

    Thanks for the bump, Matt! And Mike, I, at least, like to think it was one heck of a thesis :)

    In addition to the 3D files (all of the bits and pieces, plus a copy of the articulated skull), there are three CT scan sets included in the appendix. Feel free to go through each, slice by slice, for each element, to make sure my work is reproducible!

    And Matt, don’t feel bad about coming over to the more interesting branch of Dinosauria. The kool-aid over here tastes great, and the water’s fine!

  4. Andrew Thomas Says:

    Thank you for the gracious compliments, also, Mike :)

    Would somebody mind letting me know if the individual stl files come out articulated if you open them up together? I oriented them and saved them so that the whole skull (jaws, the whole shebang) should appear in complete articulation when more than one element’s stl file is opened at the same time (i.e., they shouldn’t all just lump together on top of each other at the origin). They open that way on my machine, but that’s what I saved them on, so I’m not sure how they’ll behave in the wild.

    Thanks again!

  5. Anonymous Says:

    “Now if we could just get some more Sauroposeidon…”

    You fool! Isn’t it obvious! Tenontosaurus is just a juvenile ontogemorph of Sauroposeidon. ;)

  6. Chase Says:

    If only we had fossils of this quality from the east coast
    *goes and cries in museum collections room*

  7. WELL–time to call up the UAA Engineering Department again. They printed my dear Aquilops skull, and I suspect they’ll be willing to print out another stinkin’ ornithischian skull. :-)

    Wonderful work, Andrew, and thank you for including 3D print files for all us armchair enthusiasts!

  8. Matt Wedel Says:

    Andrew wrote:

    And Matt, don’t feel bad about coming over to the more interesting branch of Dinosauria.

    If you’re referring to Ornithischia in general, that is disturbing enough. The possibility that you might mean Ornithopoda is truly vile. This is a family site, Thomas.


    Tenontosaurus is just a juvenile ontogemorph of Sauroposeidon.

    I am smiling through my tears, for several reasons.


    If only we had fossils of this quality from the east coast

    WORD. There have to be some really interesting evolutionary and biogeographic stories lurking in the Arundel, if only we could get decent material out of it. (And if less of it was paved over!)

  9. jrabdale Says:

    I really must use the word “flarkjillion” more often in everyday conversation.

  10. Mike Taylor Says:

    Unless it’s skeletons of ceratopsians, of course. Then the SI standard unit is the farkejillion.

  11. Ben Says:

    “There have to be some really interesting evolutionary and biogeographic stories lurking in the Arundel, if only we could get decent material out of it. (And if less of it was paved over!)”

    Believe me, we’re looking! And all this great work coming out of other Aptian sites makes us try even harder…

  12. Matt Wedel Says:

    Oh, I know, and I salute you. There needs to be some kind of trans-continental support group for workers in the North American Lower Cretaceous outside of the absurdly productive Cedar Mountain Formation and reasonably productive Cloverly.

  13. Mike Taylor Says:

    Meanwhile, we over here in the UK are just grateful someone has a scrappier dinosaur record than us.

  14. Mark Robinson Says:

    Meanwhile, we over here in the UK are just grateful someone has a scrappier dinosaur record than us.

    Er, hello from Western Australia!

  15. Chase Says:

    I couldn’t agree more Matt. It seems that in recent years more workers have paid attention to the dinosaurs of the east coast. More specimens from the Arundel clay would put a smile on my face, but ultimately I wish for more specimens from the Marshalltown, Navesink/New Egypt, and Black Creek formations of New Jersey and North Carolina that would further our understanding of the Late Cretaceous in the Eastern United States.

    Mike, I feel your pain.

  16. J. Says:

    I know I’m late commenting and you don´t know me, but I can´t help but to wonder after reading the above… what can you deduce from the hyoid and inner ear bones of Tenontosaurus? Anything about tongue size/shape, or about its sense of hearing and balance worth sharing?

  17. Andrew Says:

    Balance info is pretty likely from the inner ears. I didn’t come across any inferences based off the hyoid in my research. Doesn’t mean there aren’t any, but I think the inner ear is more information dense. The problem with hyoid is also related to the paucity of material; only a handful of other ornithopods are preserved with them.

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