Stegosaurus posture

[Wade Thompson]

Hello everyone. Whenever I see paleoart that depicts Stegosaurus, paleoartists tend to depict it in two different ways and I’m curious as to what is the more correct version.

The first way they depict it is with a shorter body length, a taller back, a shorter tail and overall a more I guess “square appearance”. If I remember correctly this is based on Usnm 4934. As for an example of a reconstruction that depicts stegosaurus like this, there is randomdinos skeletal reconstruction of stegosaurus stenops.

The second way they depict it is more like Sophie. They depict it as longer and much more similar to other members of the stegosaur family. An example of a reconstruction that depicts stegosaurus like this is Scott Hartmans skeletal. Now if I remember correctly, Sophie was not a full grown adult and if remember correctly the forelimbs don’t stay proportional to the hind limbs when Stegosaurus was fully grown unlike Sophie. If I remember correctly, when Stegosaurus was fully grown the vertebrae toward the sacrum got quite tall unlike in Sophie. Do correct me if I wrong though. Anyways what I just said is why I’m skeptical of all those Stegosaurus reconstructions that depict it like Sophie. However at the same time I still see plenty of reconstructions of Stegosaurus that depict it like Sophie. That would imply that Sophie is useful for reconstructing adult Stegosaurus despite being a sub adult. At the same time however I still see depictions of Stegosaurus in modern paleoart that depict it more squared, so I’m curious. What is the right way to depict the posture of Stegosaurus?

[Gregory Paul]

I have a paper on this in review, and this will also be in my ornithischian field guide. Sophie (A in attached) is not S. stenops (B) -- in part because it has a peculiar set of chest ribs that result in a longer functional neck -- but is not an adequate holotype because is a juvenile and other issues. The proportions of these skeletals are as usual as precise as possible. 

GSPaul

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[Richard W. Travsky]

Speaking of stegosaur posture – when did it start being depicted with the tail held higher – as opposed to low and darn near being dragged?

 

I note posture that in early media like movies, children's books, museum displays.

 

From: 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com>
Sent: Friday, March 6, 2026 8:07 AM

 

I have a paper on this in review, and this will also be in my ornithischian field guide. Sophie (A in attached) is not S. stenops (B) -- in part because it has a peculiar set of chest ribs that result in a longer functional neck -- but is not an adequate holotype because is a juvenile and other issues. The proportions of these skeletals are as usual as precise as possible. 

 

On Friday, March 6, 2026 at 09:41:55 AM EST, Wade Thompson <wt44...@gmail.com> wrote:

[Jura]

As far as I've been able to determine, the first depiction of Stegosaurus with the tail held high was Bakker's Dinosaur Heresies (S. ungulatus back when it was thought to have eight tail spikes). Bakker didn't provide any anatomical support for this view. I think he just liked it better as it aligned with the premise of the book. It wasn't until Ken Carpenter (1998) analyzed the tail anatomy that we had any anatomical evidence one way or the other for tail position in Stegosaurus.

Carpenter, K. 1998. Armor of Stegosaurus stenops, and the Taphonomic History of a New Specimen from Garden Park, Colorado. Mod. Geol. Vol. 23:127–144.

[Stephen Poropat]

There are much older images than that which show Stegosaurus with a raised tail.

Lull (1910) included photos of a skeleton mounted with a rasied tail, and of a model of Stegosaurus ungulatus with a raised tail. (https://ajsonline.org/article/134498-stegosaurus-ungulatus-marsh-recently-mounted-at-the-peabody-museum-of-yale-university)

Abel (1925) included a photo of that model (which reminded me of Lull's work). However, the reason I went to Abel (1925) in the first place was because I remembered (from the early 2010s) perusing it in the library in the basement of the Museum of Evolution in Uppsala, and seeing a reconstruction of Stegosaurus by Gerhard Heilmann that depicted it with a raised tail as well. The book can be downloaded for free here: https://www.zobodat.at/pdf/MON-GEO_0109_0001-0327.pdf

Heilmann's reconstructions were, as many have said before, so far ahead of their time. His running Iguanodons. His nimble Compsognathus. His Triassic dinosaurs by the seashore. His lithe / svelte ornithomimids. But this stegosaur image stuck with me for whatever reason, and until I went looking for it today I probably hadn't seen it in a decade. What sets it apart from the others is perhaps the fact that Stegosaurus is a dinosaur that is so easily conceived of as being lumbering and brainless; maybe only Iguanodon of those mentioned above could be tarred with the same brush. Yet Heilmann makes his stegosaurs look so alive and alert.

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[A L]

On the topic of posture, I'm looking at some reconstructions of "Sophie" by different artists/scientists; it seems like in some of these the tip of the prepubis goes into the back of the ribcage (Please see image below). Both Hartman's (top image) and Dempsey's "Sophie" (second from top) shows this condition (tip of the prepubis highlighted in red), the original Maidment et al 2015 also shows this; while Paul (third image from top) and Randomdinos's (bottom image) illustrations shows the the tip of the prepubis stops just before the ribcage ends. If the tip of the prepubis goes inside the ribcage is the correct configuration then would this mean that there would be no or minimum waist movement range for the animal (those prongs would be hitting the ribcage as soon as it tries to rotate its waist). My assumption is that all these reconstructions have most of the distortion corrected. Does anyone know what the consensus of this condition is (as in which is the correct configuration)? Could it just simply be the artists didn't create enough intervertebral disc space in the spine of the animal (and somehow shorten or lengthen the overall body) or the spine should have a different curvature?

[Gregory Paul]

To the best of my knowledge the prepubis never is medial or lateral to the ribs. Indeed, in a number of ceratopsids one of the posterior edges of the posterior ribs has an articular surface that articulates with the anterior rim of the prepubis, this is true of the skull less "Anchiceratops" skeleton, the AMNH Centrosaurus, and other cases. In the case of ceratopsids was probably a feature for strengthening the ribcage for intraspecies flank combat. 

GSPaul

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[Michael Habib]

Good observation Greg - it also seems that the posterior ribs in crocodilians and birds align more or less with the anterior edge of the ilium (even though they don’t touch the pelvis). Bringing the ribs into alignment with the prepubis seems quite workable for the adult specimens pictured - but I’m curious how this could work with Sophie. Any thoughts?

Oh, and just a quick note about the vertebral column in these animals: they did not have intervertebral discs. That’s a mammalian condition. The intervertebral joints are all synovial in reptiles (standard vertebrate condition).

Cheers,

—Mike H.

> On Mar 11, 2026, at 8:59 PM, 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:
>
> To the best of my knowledge the prepubis never is medial or lateral to the ribs. Indeed, in a number of ceratopsids one of the posterior edges of the posterior ribs has an articular surface that articulates with the anterior rim of the prepubis, this is true of the skull less "Anchiceratops" skeleton, the AMNH Centrosaurus, and other cases. In the case of ceratopsids was probably a feature for strengthening the ribcage for intraspecies flank combat.
>
> GSPaul
>
> On Wednesday, March 11, 2026 at 10:54:43 PM EDT, A L <boatp...@gmail.com> wrote:
>
>

> On the topic of posture, I'm looking at some reconstructions of "Sophie" by different artists/scientists; it seems like in some of these the tip of the prepubis goes into the back of the ribcage (Please see image below). Both Hartman's (top image) and Dempsey's "Sophie" (second from top) shows this condition (tip of the prepubis highlighted in red), the original Maidment et al 2015 also shows this; while Paul (third image from top) and Randomdinos's (bottom image) illustrations shows the the tip of the prepubis stops just before the ribcage ends. If the tip of the prepubis goes inside the ribcage is the correct configuration then would this mean that there would be no or minimum waist movement range for the animal (those prongs would be hitting the ribcage as soon as it tries to rotate its waist). My assumption is that all these reconstructions have most of the distortion corrected. Does anyone know what the consensus of this condition is (as in which is the correct configuration)? Could it just simply be the artists didn't create enough intervertebral disc space in the spine of the animal (and somehow shorten or lengthen the overall body) or the spine should have a different curvature?<comparison_RED.png>

>
> On Wednesday, March 11, 2026 at 4:22:50 PM UTC+11 Stephen Poropat wrote:
> There are much older images than that which show Stegosaurus with a raised tail.
>
> Lull (1910) included photos of a skeleton mounted with a rasied tail, and of a model of Stegosaurus ungulatus with a raised tail. (https://ajsonline.org/article/134498-stegosaurus-ungulatus-marsh-recently-mounted-at-the-peabody-museum-of-yale-university)
>

> Abel (1925) included a photo of that model (which reminded me of Lull's work). However, the reason I went to Abel (1925) in the first place was because I remembered (from the early 2010s) perusing it in the library in the basement of the Museum of Evolution in Uppsala, and seeing a reconstruction of Stegosaurus by Gerhard Heilmann that depicted it with a raised tail as well. The book can be downloaded for free here: https://www.zobodat.at/pdf/MON-GEO_0109_0001-0327.pdf
>
>
>

> To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/1102704362.160127.1773287968954%40mail.yahoo.com.
> <comparison_RED.png>

[Heinrich Mallison]

The Triceratops in Melbourne was found articulated.

There is NO WAY you can articulate the posterior ribs to the vertebrae in a way that leaves the prepubis free in lateral view. Also, there is no way you can articulate things so the tips of the prepubes are not somewhat medial of the posterior ribs. You can't get them into the "body wall", so to speak. There isn't much overlap, nor is there much space between ribs and prepubic tip, but the position is clearly "tips of prepubes medial to the posterior ribs". 

see e.g. https://camd.org.au/mvs-triceratops-fate-of-the-dinosaurs/

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[Jura]

As is often the case, the devil is in the details here. Most reptiles (studied) show a version of a diarthrotic joint as Mike describes, but crocodylians have convergently evolved intervertebral discs similar to (but thinner than) mammals (Fauble et al. 2020). There is also some inferential data to suggest that intervertebral discs may have been more prominent in extinct reptile groups (Wintrich et al. 2020), especially the marine critters.

Refs

Fauble, K., Adams, J., Gerdes, M., Vansickle, C. and Young, B.A., 2020. Compressive biomechanics of the reptilian intervertebral joint. Journal of Zoological Research, 2(4). 

Wintrich, T., Scaal, M., Böhmer, C., Schellhorn, R., Kogan, I., van der Reest, A. and Sander, P.M., 2020. Palaeontological evidence reveals convergent evolution of intervertebral joint types in amniotes. Scientific Reports, 10(1), p.14106.

[Andreas Johansson]

Is there any evidence of intervertebral discs in pan-Aves?

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Andreas Johansson

Why can't you be a non-conformist just like everybody else?

[Gregory Paul]

The first to note the direct connection between the posterior ribs and the anterior end of the prepubis in ceratopsids was Ozzie in 1933 regarding the AMNH Triceratops (https://www.biodiversitylibrary.org/item/346053#page/1/mode/1up) who said "The thirteenth thoracic is especially important, since it forms a ligamentary connection near the near the middle of the of its length with the anterior end of the prepubis, the thickness of the bone for this articulation and the surface being very clearly marked. In previous mounts the prepubis has been placed inside the posterior rib." O mounted the skeleton in this manner (his Fig. 8). 

The articulated juvenile Triceratops has a posterior rib articulating with the end of the prepubis (https://x.com/DavidEvans_ROM/status/1167942780896735234/photo/2). 

And there is the "Anchiceratops" skeleton https://prehistoric-wiki.fandom.com/wiki/NMC_8547?file=Anchiceratops_ornatus_skeleton.jpg in which the robs are arced to be ahead of the prepubis. This shows that some ceratopsid ribcages were dense packed as a form of armor. 

I have not seen examples of well articulated ornithischian skeletons in which ribs are astride the prepubis (in the Smithsonian road kill Stego both the ribs and prepubis are displaced). Have not found good pics of the Melbourne Triceratops in-situ. Nor of the Dueling Dinosaur. 

I think the Anchi skeleton first clued me in to the situation, and then the Osborn paper, though that could be reversed. I first discussed this in the 1987 Dinosaurs Past & Present chapter, the Gakken book a few years later, the Scientific American Book of the Dinosaur around the turn of the century (still in libraries which is not the best thing it being old fashioned) and the dino field guides. 

GSPaul 

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[Mike Habib]

On Mar 11, 2026, at 11:54 PM, Jura <arch...@gmail.com> wrote:

As is often the case, the devil is in the details here. Most reptiles (studied) show a version of a diarthrotic joint as Mike describes, but crocodylians have convergently evolved intervertebral discs similar to (but thinner than) mammals (Fauble et al. 2020).

Excellent correction. It should be noted, though, that the crocodilian joints are still synovial. The fibrocartilage septum is expanded into a significant compressive load bearing structure, appearing superficially similar to a mammalian IVD. The synovium has not been lost, however (so far as I’m aware - I might have missed something). The mammalian IVD is, therefore, unique.

Interestingly, the reptilian version of the IVD is probably quite old, with some reversals to standard synovial joints: https://www.nature.com/articles/s41598-020-70751-2.

So far as I’m aware, there are no reversals in mammals (probably because the joints are no longer synovial at all), though it’s worth noting that the joint between the bodies of the atlas and axis remains synovial in mammals.

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[Heinrich Mallison]

If you search for Raymond on the net, you will find other images taken at other times, where the ribs are in a different arrangement. The photo you link, Greg, is NOT the position it was found in (as one can easily tell from the exactly parallel rib shafts).

As for laterally compressed articulated specimens in general: you can't take their exact rib position at face value! Especially in specimens like the NMC one that were later "improved" for display. SHow me true undeformed and in 3D how this works, then I believe it.

(Also, may I point out that the German saying "paper is patient" applies, too? https://www.app.pan.pl/article/item/app20090075.html)

There will soon be, I hope, a big paper on an articulated Triceratops with 3D files published. Then all can see for themselves. 

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