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Roofed-reptile overhaul by ScottHartman Roofed-reptile overhaul by ScottHartman
Stegosaurus, one of the most popular non-theropod dinosaurs. 

2016 update: As strange as it must seem given how often Stegosaurus has been portrayed and how many specimens are known (for well over a century!), but we actually knew surprisingly little about the basic proportions of Stegosaurus until very recently. That's because previous specimens were either not prepared out all the way (to preserve taphonomic data) or were mounted as composite specimens.

That all changed last year when Maidment, Brassey, & Barrett published the Sophie specimen: journals.plos.org/plosone/arti…
Among other things it turns out that Stegosaurus has more cervicals and fewer dorsals had been previously been thought. This results in a less tall-bodied and longer-necked animal. In retrospect perhaps this isn't shocking - Kentrosaurus appears to also have had a longer neck than some early reconstructions suggested, and of course Miragaia took this one extra step in its neck-elongation.

Another odd feature is that the tail has a distinct down-curve in the posterior portion. I've gone over the distal caudals several times and the downcurve does not seem like a preservational artifact, so I'm including it in the reconstruction. One interesting side-effect of this is that the thagomizer is now oriented at a more useful angle for swinging at an attacker (I do not consider the laterally-facing spike suggestion to be likely), and notably other stegosaurs also seem to have their distal tail spikes end up facing closer to horizontal as well, either through tail articulation or by changing the angle of the spikes.

So now Stegosaurus does not stand out quite as drastically from its close relatives. It still looks pretty cool though, if you ask me.
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:iconpaleo-reptiles:
Paleo-reptiles Featured By Owner Dec 27, 2016

Dear Scott Hartman

Plates shape are different in these two models. Even Pelvis shape that was discovered, have differences with each other.

Therefore, Are you Sure these two models are the same species?


Why do you delete the previous model of your website and deviantart?

Reply
:iconscotthartman:
ScottHartman Featured By Owner Dec 28, 2016  Professional Digital Artist
Excellent questions Amin, and some of the questions are easier to answer than others. Remember that before Sophie specimen that all current mounts (and all the skeletals based on them...including my earlier one) were based composite mounts (that is, mounts made up of several specimens) and on specimens that were not fully prepared from the rock (e.g. the "road-kill" specimen at the USNM), so they all had to make assumptions to fill in or cross-scale the gaps in our knowledge.

Sophie is very complete, and shows that some of those assumptions are just wrong - e.g. the number of vertebrae in the neck and torso (and thus the relative lengths of the body and neck). The pelvis is generally squished or incomplete in a number of specimens, so I'm not 100% sure whether the differences are due to some sort of variation in age, sex, species, etc. Certainly the relative length of the retroverted pubis and ischia could have varied between the sexes, since the depth of those bones directly impacts the size of eggs that could have been laid - but with so few good specimens we just don't know for sure.

The plates really do seem too variable to be explained away like this, and also we have lots of good plates (though rarely such a complete series as in this example). Several researchers have suggested that there might be some sort of sexual dimorphism involved between males and females, which would explain why there is such a large variety of plate sizes in the Morrison. But until we get enough specimens to test this hypothesis (as opposed to different ages, species, etc.) we won't know for sure.
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:iconpaleo-reptiles:
Paleo-reptiles Featured By Owner Dec 28, 2016
Thank you very much brother Scott to spent your valuable time for me.

Your answers every time show me that you are a great scientist. I am very lucky for having a wise friend like you :)

I feel writting a new book about prehistoric reptiles are not easy like past. everyday, a new information will be discovered and theories change very fast. In past, we have new changes every decades. but Now, it is every month. publish a new book is not easy in such condition. but It is necessary we have a new book even if next years its information and pictures are out of date according the more research.

I hope you and your friends in USA publish a new encyclopedia about new modeles of prehistoric reptiles . Now, the interesting books that G. S. Paul published cannit give us a correct imagination about anatomy of these wonderful animals.  
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:icondinosaurzzz:
Dinosaurzzz Featured By Owner Dec 27, 2016
Would all stegosaurs have this tail shape, or just Stegosaurus?
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:iconscotthartman:
ScottHartman Featured By Owner Dec 28, 2016  Professional Digital Artist
Kentrosaurus seems to have a bit of a curve also, but it's not this strong. I'd guess that the character is pretty variable, especially since the number of "spikes" varies in other taxa, and so tail-use might have varied quite a bit as well.
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:icondinosaurzzz:
Dinosaurzzz Featured By Owner Dec 28, 2016
Huh, ok. What about Hesperosaurus, would it also have a curve?
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:iconscotthartman:
ScottHartman Featured By Owner Dec 28, 2016  Professional Digital Artist
I wish I knew!
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:icondinosaurzzz:
Dinosaurzzz Featured By Owner Edited Dec 28, 2016
Would it be equally as accurate to restore it with and without one?
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:iconpaleo-reptiles:
Paleo-reptiles Featured By Owner Dec 25, 2016
Dear friend, Scott!

somtimes, if fossils exist in museums , why everytime, reconstractions show strange changes? I was surprised how the great experts were blind for watch things that they see them now.

Please answer to my quesions:

1- You had a nice stegosaurus like reconstraction by G. S. Paul. but Now, You delete it. Why?

2- Why the shape of large plates in back of your new version  is different of your previous version?

3- Even numbers of paltes changed. Why?

4- in your previous version, large plates have a much of dark part that show they grow like horn of rhino . but now, do not exist such high dark part in large plates of your new version.... but why?

I like the curve shape of end of its tail because it is logical for attack to predators now. but How stegosaurus can lay down or sit down with such curve?
Reply
:iconscotthartman:
ScottHartman Featured By Owner Dec 28, 2016  Professional Digital Artist
So the reality is that museums are just doing their best, and despite public perception the main purpose of most publicly funded museums is to support scientific research, not to constantly update their displays (which would be enourmously expensive). As a result, displays are often put together by people who are not scientists themselves, and they often copy what has been done in other museums previously rather than reading the current scientific literature. In this case, most museum displays of Stegosaurus from the early 1900s until the 1980s largely just repeated mistakes that Marsh had made, sometimes with some of the corrections made in papers from the 1910s and 1920s (but there still were lots of unknowns at the time). Because Stegosaurus is so distinctive with its plates and spikes and tiny head, dinosaur books almost always tried to portray them, and museums wanted casts to mount, so the image of Stegosaurus became much more entrenched in our collective imagination then the science itself warranted - sort of the same way that swamp-dwelling sauropods did.

Several paleontologists and artists started revising what we know about stegosaurs starting in the 1970s, but these weren't usually done because of new specimens, they were just correcting anatomical inferences that were no long seen as correct (like the lizard-like sprawling forelimbs), but areas where we just didn't know the answer (like vertebral count) couldn't be corrected without newer, more complete specimens.

I was also surprised by how extreme the changes were - it's not often that a well-known species goes through this sort of change anymore, but as I said here and elsewhere, if we'd looked a bit closer it would have been clear that there were more gaps in our knowledge of Stegosaurus anatomy than people realized. 

Now for your questions:

1) My previous reconstruction was based on a composite of several excavated by and displayed at the Museum of Ancient Life at Thanksgiving Point, Utah. I used the specimen because I had access to casts of it, but I was still stuck with the assumptions they made. My best guess is that they used Greg Paul's skeleton to try and decide how to combine the incomplete specimens they used, which is why they had similar vertebral counts, etc. I deleted it because the new skeletal based on Sophie is definitely more correct, even if some of the differences (like the shape of the plates) might be real. Perhaps some time I will get to revisit those specimens with our new knowledge from Sophie, but until I do (and see them first hand so I know which specimens are which) I have pulled it from my website because it's now out of date.

2) Different specimens. There's actually quite a lot of variation in plate shape and size in Stegosaurus, and it might suggest that the males and females of each species had differently shaped plates (and presumably there were differences between the species themselves), but as is usually the case we don't have a large enough sample to test this statistically. And in the case of the Morrison itself we also don't have good enough temporal constraints, since the Morrison is ~9 million years long and each lineage of dinosaur probably also shows variation over that timespan (indeed, that's probably why it looks like sauropod diversity is so high in the Morrison - because Apatosaurus, Camarasaurus, etc., were all evolving across that time into 2-4 distinct "morphs" that we've named different species).

3) The Sophie specimen has the most complete set of plates, and it shows there were more than people had inferred from earlier, more complete specimens.

4) That just reflects changing ideas about how thick the keratin layer was - some of the histological work has hinted that it wasn't as thick as my previous skeletal showed. It's just a coincidence that the new specimen came out before I got around to changing the keratin thickness on the old one.

5) The curve is just the neutral position, it's not fused into that shape. I'm sure it could at least partially straighten it when laying down.

Cheers!
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:iconpaleo-reptiles:
Paleo-reptiles Featured By Owner Dec 28, 2016
Thank you very much brother Scott for your perfect answer :)
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:iconthedilophoraptor:
TheDilophoraptor Featured By Owner Dec 8, 2016  Hobbyist General Artist
Is it possible that Sophie is actually a Hesperosaurus?
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:iconscotthartman:
ScottHartman Featured By Owner Dec 10, 2016  Professional Digital Artist
I suppose it's possible, but the authors don't think so, and they're in a pretty good position to know.
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:icontigris115:
tigris115 Featured By Owner Dec 8, 2016
Firstly, is this one full grown? Second, what about the proportions of ungulatus and other species
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:iconscotthartman:
ScottHartman Featured By Owner Dec 10, 2016  Professional Digital Artist
It's not full grown, but it's close enough that I wouldn't expect it to change proportions much. At this point I think we have to accept that the classic view of Stegosaurus proportions may not be correct for any of the species - we'll need more data to know for sure though.
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:icondinocarid:
DINOCARID Featured By Owner Dec 2, 2016  Hobbyist Traditional Artist
This is a very interesting new light on this animal.
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:iconscotthartman:
ScottHartman Featured By Owner Dec 3, 2016  Professional Digital Artist
Isn't it? I still shake my head sometimes when I look at it, but the new specimen is pretty unequivocal (and the older ones are surprisingly not so)
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:icondavetriarchy:
Davetriarchy Featured By Owner Nov 28, 2016  Hobbyist Digital Artist
Species name?
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:iconscotthartman:
ScottHartman Featured By Owner Dec 3, 2016  Professional Digital Artist
In the paper it was described as S. stenops. There are of course some ongoing debates about lumping vs splitting stegosaur taxonomy, but I think S. stenops is reasonable.
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:icondavetriarchy:
Davetriarchy Featured By Owner Dec 3, 2016  Hobbyist Digital Artist
Okay, thanks.
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:iconheinrichm:
HeinrichM Featured By Owner Nov 8, 2016
Scott, I ain't too sure about that supposed down-turn in the distal tail. Given the strong forces acting on the tail tip during thagomization I would not be surprised if the intervertebral tissues were more wedge-shaped than we see further anteriorly or in other dinosaurs.
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:iconscotthartman:
ScottHartman Featured By Owner Nov 9, 2016  Professional Digital Artist
Maybe so, but first principals for skeletal reconstructions include the idea that the way centra and zygapophyses fit together means something. And it's not one or two isolated caudals, it's the whole last 1/5th or so. 

Of course I'm always happy to update it later if more/better evidence emerges.
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:icondovahkiinhu3br:
DovahkiinHU3BR Featured By Owner Nov 3, 2016
Who ever made The Isle's stegosaurus made a head shot with no scope then.
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:iconscotthartman:
ScottHartman Featured By Owner Nov 5, 2016  Professional Digital Artist
Clearly a sniper.
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:icondovahkiinhu3br:
DovahkiinHU3BR Featured By Owner Nov 5, 2016
With no scope... someone is addicted to FPS games.
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:iconxstreamchaosofficial:
XStreamChaosOfficial Featured By Owner Nov 2, 2016  Hobbyist Traditional Artist
Wow! Just wow! So beautiful! I love how the specimen finally made our depiction of Stegosaurus just way more realistic! It brought tears to my eyes and a warm feeling in my chest! Just peer awesome! This is definitely a game changer and I can't wait to draw the more accurate Stegosaurus! :D
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:iconscotthartman:
ScottHartman Featured By Owner Nov 5, 2016  Professional Digital Artist
I'm glad it had such a positive impact on your day :)
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:iconarchanubis:
Archanubis Featured By Owner Nov 2, 2016
So I gather that Stegosaurus stenops et all didn't have plates as massive as most depictions of Stegosaurus have (especially over the back and hips)?  Is that a correct assumption?
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:iconscotthartman:
ScottHartman Featured By Owner Nov 5, 2016  Professional Digital Artist
Some other specimens do appear to have plates that are broader anterior-posteriorly. Whether that is individual variation, ontogenetic, or something to do with taxonomic or temporal variation isn't really something we can ascertain with our current sample of specimens.
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:iconprincetarbos:
Princetarbos Featured By Owner Nov 2, 2016
A beauty. Would adults look similar to this?
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:iconscotthartman:
ScottHartman Featured By Owner Nov 5, 2016  Professional Digital Artist
Should be pretty close - this is a subadult, not a juvenile. Maybe the plates change shape or size in adults (or one or the other sex of adult?) but with our current sample size that's just speculation.
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:iconprincetarbos:
Princetarbos Featured By Owner Nov 5, 2016
Wow, that sounds amazing!!!
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:icontyronemf:
TyroneMF Featured By Owner Nov 2, 2016  Student Traditional Artist
nice bones
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:iconszymoonio:
Szymoonio Featured By Owner Nov 2, 2016  Professional Digital Artist

On some reconstructions Stegosaurus had too short tail, now it looks more functional in defense. Good job :)
-Szymon

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:iconmistingwolf:
MistingWolf Featured By Owner Nov 1, 2016  Hobbyist General Artist
Stegosaurus is still my favorite herbivorous dinosaur; the new reconstruction just makes me love it more.
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:iconscotthartman:
ScottHartman Featured By Owner Nov 1, 2016  Professional Digital Artist
I'm glad the changes only enhanced your enjoyment of it.
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:iconantonellisofbbender:
AntonellisofbBender Featured By Owner Nov 1, 2016  Student Filmographer
this skeleton the most accurate stegosaurus skeleton?
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:iconscotthartman:
ScottHartman Featured By Owner Nov 1, 2016  Professional Digital Artist
I would say so, yes.
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:iconantonellisofbbender:
AntonellisofbBender Featured By Owner Nov 1, 2016  Student Filmographer
if that is true than can i use this image to make an accurate stegosaurus 3d model on blender and animate it?
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:icond-juan:
D-Juan Featured By Owner Edited Nov 1, 2016  Student General Artist
And also a thicker tail and neck!
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:iconthedinorocker:
thedinorocker Featured By Owner Nov 1, 2016
This is a fantastic update!
"Sophie" is a stunning specimen
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:iconscotthartman:
ScottHartman Featured By Owner Nov 1, 2016  Professional Digital Artist
Agreed, Sophie is pretty great.
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:iconthedinorocker:
thedinorocker Featured By Owner Nov 1, 2016
In the description paper the authors lists the specimen sa S.stepos, so actully the Stegosaurus genus is monospecific With Mjosi and Longispinus in their own genus?
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:iconscotthartman:
ScottHartman Featured By Owner Nov 1, 2016  Professional Digital Artist
I believe Susie Maidment has found S. longispinus to be a nomen dubium, and sunk all other Stegosaurus species except mjosi into S. stenops. I'm less sure about what is going on with S. mjosi in their book. The Morrison Formation taxa are particularly challenging taxonomically because it's 9 million years long (give or take) so some of the "species" variation we see are probably just anagenetic changes.
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:iconthedinorocker:
thedinorocker Featured By Owner Nov 1, 2016
Thank You...
yes 9 milions years is infinite long time, and anagetics changes are something se see in Triceratops in a relative short time
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:iconfancypancakes:
FancyPancakes Featured By Owner Edited Oct 31, 2016  Professional Digital Artist
Beautiful reconstruction!

This sparks a memory of when was given the opportunity to look at a stegosaurus fossil behind the curtains last year (at a fossil/mineral shop called Red Gallery in Hamburg, Germany). What was curious about this specimen though is that it seemed to have an additional row of tail spikes? My memory is a bit foggy unfortunately, but I clearly remember the guide talking about it as if it was a recent discovery. It also had a bite mark from an Allosaurus on one of its back plates that had healed.
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:iconscotthartman:
ScottHartman Featured By Owner Nov 1, 2016  Professional Digital Artist
Huh, sounds cool. I can't really comment usefully until I either see the specimen or it gets published, but I'd certainly look forward to it.
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:iconfancypancakes:
FancyPancakes Featured By Owner Nov 1, 2016  Professional Digital Artist
Yep, I've been waiting for it to get published ever since, too. I hope it wasn't sold to a private collection before it could be studied though, I believe it was on sale after all.
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:iconmidiaou:
Midiaou Featured By Owner Oct 31, 2016  Hobbyist General Artist
Pretty cool, Scott. I'll have to delve into the paper myself. So what sort of motion would you think the tail made? How would it be used? 
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:iconscotthartman:
ScottHartman Featured By Owner Oct 31, 2016  Professional Digital Artist
Victoria Arbor refers to them as a flail-like device (as opposed to a club), but whether the flail model or the fencing model is correct depends on a better understanding of what the vertebrae allow, as well as what impediment the plates played in potentially restricting tail movement.

I guess that's just a long-winded way of saying I don't know.
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