Stegosaurus' design through the years

[foxilized]

Hi. I bring a new little study of the history of designs in paleoart. This time, STEGOSAURUS:


The first stego fossils ever were found by MARSH in 1877. He described it as having a double file of sheets on its back, but in the drawing he made he put only one file.



Maybe MARSH did it to make the drawing more clear, but this cause a lot of paleoartists of the time commit the mistake of designing it wrong (we might guess paleoartists don't read the texts, only watches the pictures

1892, by JOSEPH SMITH



1897, by CHARLES KNIGHT



1902, by F. JOHN



1904, by CHARLES KNIGHT




At some point, the paleopainters should have realized there was some text besides MARSH's drawing of the skeleton, and that the animal actually had TWO files of sheets. Allrighty, now they made the appropiate change in the design and put 2 files. But there were parallels, with each sheet in front of the other:

1905, by JOSEPH SMITH



1912, by CHARLES KNIGHT



1916, by HEINRICH HARDER




At the same time, there were a couple of guys who dreamed a stego ala pangolin, with the sheets forming some kind of armor:

1914, by FRANK BOND




Not till 1920's the paleoartist finally got the design of the alternate sheets:

1929, by CHARLES KNIGHT



From that painting, KNIGHT also sculpted a model:



His admirer ZDENECK BURIAN took that design and made it his, and spread it over books and popular culture from the 40's to the 70's:




Till the 70's, the sheets had been considered and depicted in the paleopaintings as some kind of defensive quills, but then this theory changed and now were considered temperature regulators, which the animal oriented to the sun to receive the energy into its blood:

by GIULIANO FORNARI




The stego suffered another important aesthethic operation: the tail was not touching the floor anymore, but straight and parallel to the floor (and the spikes of the end now are thought to be also paralell to the floor, and not vertical anymore as allways depicted). Still, the idea of the sheets being a defensive weapon (combined with the use for temperature regulation) was defended by Robert Bakker who believed the creature could move them with some muscles on its back and point the sharped peaks to the enemies:





The posture of the head also was raised up, and some cheeks were added to the mouth.





Hope you liked it!

[kevin]

Actually, the plates have never been found articulated to the skeleton, and they are not attatched to the spine, just imbedded in the skin and muscle. As such, the layout of the plates has always been a point of discussion and controversery. There is not any way of proving the layout as far as I know. The current alternating plate configuration is the accepted likely one at the moment, but like so much of this, like all other dinos, is speculation. Likewise, the exacct layout of the tail spines is not known, hence the variations seen lately. I prefer the horizontal look.

As for Marsh's first drawing up there, it is a plan view, so if he thought of the plates as a parallel double row, he would not have drawn the second row.......

Oh, and there is no way to prove whether or not the plates were bone covered with skin, or bone covered in a horny keratin sheath. The fossil bone does show the grooves where blood vesels were, but these could have fed bone or horn. If horn, the plates MAY have been more useful defensively, and could have been almost any color or pattern. If just skin covered bone, there were likely quite fragile, and reddish or orangish were the likely colors, especially if flushed with blood...

[sid]

Very interesting topic, and... Yeah, we basically don't know how those plates were really arranged

Speakin' frankly, i think they could have been useful to help the animal cooling his temperature (a là elephant's ears) and also to defend himself from the predators, either scaring them off (maybe the plates were very colorful, helping Stego to look bigger and more menacing) or even, as Bakker, suggested, moving 'em with the dorsal muscles.

[Griffin]

Don't forget the changes that happened regarding the animal's head as well; the presence of cheeks.

I don't know if this really pertains to the topic but i also find it really interesting how Steven Speilberg did not include stegosaurus in the first jp movie. In the book the sick dinosaur was a steg, but Speilberg replaced it with a Triceratops because supposedly at that point they were still unsure of how to accurately depict the bizarre plated dinosaur. Many fans complained when they saw this so in the sequal, The Lost World, Speilberg made sure to include a really nice scene starring the Stegs to make up for it.

[sid]

That's right, the TLW Stego are still excellent restorations of the beast (even if a lil' bigger than they usually were), plus the scene in which they are is great

[[][][]cordylus[][][]]

I don't think steven worried a lot about accuracy.... ;D (kidding)

Stegosaurus sure is an odd dinosaur.... They also seem to have cut back on tail spikes?

[foxilized]

You are absolutely right, Griffin. The addition of cheeks has also been common in a lot of dinos designs (Iguanodon, ceratopsians...). In the case of the Stego, the cheeks and also the position of the neck was also changed (usually a straight neck with a head near the ground, now it's raised up).

The spines in the end of the tail have been lately propossed being parallel to the floor, not vertical. Like here:

www.cedargrove.k12.nj.us/north/media/images/stegosaurus1lg.jpg


About TLW, yeah I think the stego was excellent. But I love all the JP designs, even not being acurate. A huge amount of talent there. If I'm not wrong, they made a Stego sketch for the first movie, wich was never used. (I'm not sure though, to be honest).

[Horridus]

Sept 3, 2009 6:59:23 GMT @kevin said:

Actually, the plates have never been found articulated to the skeleton, and they are not attatched to the spine, just imbedded in the skin and muscle.

I thought they had been found at least semi-articulated once, and that it gave credence to the 'alternating rows' idea?

[kevin]

I have never seen a mount where they are attatched to the spine. Which is what it means to be articulated, relly. If the plates are always separate from the fossile, then any number of things could have scattered them around some....

[sid]

Sept 4, 2009 0:51:52 GMT foxilized said:

About TLW, yeah I think the stego was excellent. But I love all the JP designs, even not being acurate. A huge amount of talent there. If I'm not wrong, they made a Stego sketch for the first movie, wich was never used. (I'm not sure though, to be honest).

They are less inaccurate than some people would think (i'm lookin' at ya, Cordy! ;D ), but anyway, yes, a lot of talent indeed... Still the most impressive dinos ever seen on the big screen, at least i think all the people here can agree

[Horridus]

Sept 4, 2009 12:52:41 GMT @kevin said:

I have never seen a mount where they are attatched to the spine. Which is what it means to be articulated, relly. If the plates are always separate from the fossile, then any number of things could have scattered them around some....

Well, yeah, that's true I suppose. (Didn't really think too hard before that last one - was preoccupied by buying tat from eBay and how little money I had left - OF COURSE articulated means attached to the skeleton.) However, I do still believe that one specimen was found with the plates arranged in a pattern that was more than simple random scattering. But then I could well be wrong. Very wrong.

[Griffin]

I think the debate about the plates has something to do with the arrangement are in on a relatively complete fossil. I remember my professor addressing this. Some people think that in life the plates weren't arranged like that, its just the way they fell after the meat rotted away after the animal was dead. I don't remember all the details about it though.

[stoneage]

It's difficult to tell the arrangement of the plates since they weren't attached to bones. Most paleontologist seem to think there were two rows of alternating plates. A Stegosaur was found in 92 (Denver Museum) which is 85% complete with the plates articulated in the correct position. The plates in this specimen partially overlap: if there were two parallel rows, they'd entirely overlap, and if there was one row, they would only barely or not overlap at all. Second, there is a great deal of matrix between the plates in the new specimen, indicating that in life they were seperated by a span of space. If the animal had only one alternating row, the plates would overlap only slightly, and not have such a space between them. Thus, the only solution left is that they had two alternating rows!

Still others say this is because of changes that happened after the death of the animal.

[stoneage]

What is the purpose of the plates? Defense,heat regulation, sexual selection or species identification.

1. Defense:

The plates are too thin and they only lie along two rows on the back which doesn't provide that much protection. We have a Stegosaurus neck plate with a U-Shaped punture wound that has partially healed. The wound correlates well with an Allosaurus snout. Allosaurus didn't really have a lot of bit force. It had less then alligators, lions and leopards.

2. Sexual Selection:

Since female Stegosaurs have plates (Unless of course all the ones we have are males) they couldn't be the result of male competition or female choice.

3. Heat regulation:

Stegosaurus plates have large blood vessels leading into them and are extremely thin. It's relative Scutellosaurus and Scelidosaurus had scutes which had the same type of blood vasculature as stegosaurus plates and spikes. But they were much too small to be used for heat regulation.
Even Ankylosaurs had scutes and ossicles that were this same way.
Huayangosaurus (Middle Jurassic) had small plates intermixed with spines. If it shared a common ancestor with Stegosaurus it would be assumed the plates would serve roughly the same purpose.

Also many animals with horns or antlers have large vessels to supply blood for fast growth. They are not heat exchangers.
At the end of the Jurassic many Stegosaurs did not have big flat plates. Kentrosaurus and Huayangosaurus had mostly spikes and a few dinky plates. They were too small to use for heat exchange.

4. Species Identification:

The skeletons of Stegosaurs (like deer) below the neck are identical. While mule deer and white tailed deer look very similiar the animals themselves have different colors, and their ears and tails are different. These differences allow the different species to be able to identify members of their own species.

[Horridus]

Thanks for the info regarding the Denver Museum specimen stoneage. Certainly seems like a compelling case for having two alternating rows. Although it's often been noted that Stegosaurus plates would have been quite fragile, surely they still would have deterred predators to a degree as a weak-jawed allosaur wouldn't want a mouth full of bone? Even if the animal was a wall of flesh on the flanks, it was surely useful to at least have the top covered - particularly on the neck (where notably the underside is protected by the neck plate)? Then again, the myriad blood vessels present a problem...

[Griffin]

By looking at modern animals today, if ever you see some odd body part that doesn't seem to make much sense, chances are its for mate attraction. Just because both males and females have plates doesn't mean they couldn't be used for courtship. Look modern animals like parrots. Both males and females are brightly colored. Some species are even sexually dimorphic but both sexes are still equally bright (lory birds I believe the males are lime green with blue and the females are scarlet). In life stegosaurus may have been sexually dimorphic in the same way.

There's a possibility also that since the plates were not attached to the bone, they could be moved around. If the animal was relaxed they may have been held out to the sides parallel to the ground. When the animal wants to appear bigger and more powerful to a predator, rival or mate, the plates could be raised up.

[foxilized]

Very interesting!

I like the theory of defense as griffin explained. Not necessarily would have served as armor (too weak for that) but as a way of scaring the enemy, psychologically. Looking bigger and scarier is a technique used by every genre of animal (you know these caterpillars who pretend to be vipers, and these butterflies who have some kind of giant eyes in the wings to scare the birds). They avoid the attack before it happens, as the predator thinks twice. If the guy uses the plates (maybe coloured with big dots, looking like giant "eyes" or something) and then show the spiked tail in a "guard" pose, nobody would attack unless they are really crazy.

[Megaraptor]

Sept 6, 2009 2:31:28 GMT foxilized said:

Very interesting!

I like the theory of defense as griffin explained. Not necessarily would have served as armor (too weak for that) but as a way of scaring the enemy, psychologically. Looking bigger and scarier is a technique used by every genre of animal (you know these caterpillars who pretend to be vipers, and these butterflies who have some kind of giant eyes in the wings to scare the birds). They avoid the attack before it happens, as the predator thinks twice. If the guy uses the plates (maybe coloured with big dots, looking like giant "eyes" or something) and then show the spiked tail in a "guard" pose, nobody would attack unless they are really crazy.

The colour scheme you describe is like the Papo Steg.

[kevin]

The exact placement and use of the throat plates are just as unknown as the thagomizer and plates. It is a fun animal to figure out. I think, personally, that if the plates were used as a defense primarily, then they would have had the keratin horn, and would have been too rigid to move around. I kinda like them that way. The old Carnegie toy has an interesting attatchment design, there seems to be a ridge of muscle and fat running along the back into which the plates are imbedded.

I had not heard about the Denver specimen. That is interesting, and does seem to strongly indicate the alternating double row.

[[][][]cordylus[][][]]

Could the plates have had a web between them, to make kind of a "sail"?