Saturday, 23 July 2022

Diplodocus: A history of reconstructions - Part 1

"Sauropods are basically alien animals . . . What can be said of the habits of an animal with the nose of a Macrauchenia, the neck of a giraffe, the limbs of an elephant, the feet of a chalicothere, the lungs of a bird, and the tail of a lizard?" is a rather well-known quote made by paleontologist Walter Coombs (1975) in a paper about sauropod life habits. Over the past 50 years our understanding of these giant dinosaurs has greatly improved, but Coombs’ initial assessment about these animals and their skeletons still holds at least some truth. Like Stegosaurus, there is simply nothing like these animals alive today and it should be no surprise that many paleontologists in the past had some considerable trouble imagining them as living beings. Today we will therefore go through the history of one of the most well-known sauropods: Diplodocus.

Earlier Sauropod Reconstructions

Fig. 1.

Diplodocus may be among the longest known, but certainly was not the first known sauropod. The first remains of such creatures, vertebrae and some limb bones, were uncovered in 1825 in Oxfordshire, England. When first sent to French vertebrate paleontologist George Cuvier, he simply identified them as belonging to a whale, despite coming from Mesozoic aged sediments. In 1841, a year before he would coin the name Dinosauria, Richard Owen examined the bones more closely and correctly identified them as belonging to a large reptile, not just because of the age, but also because the vertebrae were hollow (whale bones, like in most mammals, are solid). However, Owen would not go on to include the giant reptile in his definition of Dinosauria. Instead, he interpreted the animal as being a large relative of crocodilians, giving it the name Cetiosaurus, literally meaning “whale-lizard”. If ichthyosaurs and plesiosaurs were the Mesozoic equivalent to dolphins and pinnipeds, he believed Cetiosaurus was the reptilian version of an orca or sperm-whale, a giant marine crocodilian hunting the more diminutive sea-dwellers. Unfortunately for us, there exists no life reconstruction of Owen’s Cetiosaurus, at least not one made during the 19th century, though I imagine it looking similar in his mind to Jurassic World’s version of Mosasaurus. The above image you see is actually a mockery of the concept, drawn by John C. McLoughlin in 1979.

In 1850 Gideon Mantell re-examined additional material that was previously referred to Cetiosaurus and classified them as distinct enough to be their own genus, Pelorosaurus. He also correctly identified that Pelorosaurus was a large, land-living reptile and likely among the Dinosauria. The remains were still highly incomplete, so nothing was yet known of the characteristic long neck and tail of sauropods. As Mark Witton has already extensively written, life reconstructions from this period of sauropod research are pretty much non-existent until the 1880s.

Fig. 2

The first largely complete skeletons would instead come about during the Bone Wars between Marsh and Cope. The first hint towards the true shape of sauropods came in 1877 with Edward Cope’s description of Camarasaurus, with John A. Ryder reconstructing what was then known of the skeleton as best as he could.

Fig. 3.

The first life reconstruction of a sauropod, Atlantosaurus specifically (today a nomen dubium), appeared in 1886, being made by a certain J. Blanedet in a book called Le monde avant la création de l'homme (The World before the Creation of Man), by Nicolas Camille Flammarion. Given what was known at the time, it is actually surprisingly good, I would say, and takes many cues from modern monitor lizards, which is something actually seen again in many modern reconstructions, as the nasal cavities of monitors and sauropods do have some interesting similarities. Regarding the author of the book, Flammarion is actually more well-known for his writings on extraterrestrial life, helping perpetuate the belief of artificially made canals on Mars alongside Percival Lowell. Some connections you simply cannot escape.

Fig. 4.

The first truly classic sauropod skeletal came in 1896 with Marsh’s restoration of Brontosaurus. As is now famously known, Marsh did not know what the head of Brontosaurus actually looked like and when the skeleton was displayed in the Peabody Museum, it was reconstructed based off the heads of macronarian sauropods, such as Brachiosaurus

Fig. 5.

Cope briefly toyed with the idea that sauropods were giraffe-like high-browsers mainly living on land, but eventually he, Marsh and many other researchers at the time, fell back into the aquatic paradigm that Owen had laid out. Despite the strong, pillar-like legs, it was thought that sauropods must have lived most of their life in the water, in order to hold up all their weight, and used their long necks either as snorkels or to forage for aquatic plants. The latter was seemingly corroborated by the very small heads and strange teeth of sauropods, which at the time indicated that these animals could take in only little food and were bad at chewing, limiting their diet to soft aquatic plants and their metabolism to a low, reptilian level. Thus was born the classic image of the sluggish, cold-blooded, swamp-bound sauropod, which was possibly first illustrated in 1897 by Charles R. Knight in an article titled Strange Creatures from the Past for the Century Magazine (making it one of Knight’s oldest published pieces of paleoart). The genus depicted is Amphicoelias.

Fig. 6.

What is little known is that the drawing is based off an older sketch by Cope, seen above, which is actually rather mysterious, as its dating is unknown and Cope rather explicitly drew the animals as being bipedal, kind of like a giant version of a modern Plateosaurus. While the sketch is usually dated to around the same time as Knights’ drawing, Adrian Desmond (1975, p. 220) suspected that it could actually be significantly older, possibly from the 1870s, when it was still thought most or all dinosaurs were bipeds. If true, I propose that this image may attest to a very brief period in the timeline of sauropod research where these animals were imagined as giant bipeds.

From D. longus to D. carnegii 

Fig. 7.

The genus Diplodocus was first described by O.C. Marsh in 1878 based off remains (YPM VP 1920) from the Garden Park quarry in Colorado, which were discovered by Benjamin Mudge and Samuel Williston. The specimen was very incomplete, consisting mostly of vertebrae, and yet it became the type specimen of Diplodocus longus. If described today, it would almost certainly be viewed as a dubious taxon, though an appeal to the ICZN in 2016 to make the later D. carnegii skeletons the new type for Diplodocus has failed. Until 1884, various new remains were uncovered and assigned to D. longus, among them USNM V 2672, a complete and articulated skull, which was also the first skull of a diplodocid known. Remember this specimen, we will come back to it in part 2.

Fig. 8.

Because of its fragmentary nature, no skeletal or life reconstruction exists of Diplodocus from the 19th century. However, as soon as the century turned, this changed. In 1899 and 1900 Jacob Wortman, John Bell Hatcher, William Jacob Holland and Charles Gilmore, with funding by Andrew Carnegie, uncovered two largely complete Diplodocus skeletons at Sheep Creek in Wyoming, CM 84 and CM 94. In 1901, Hatcher made CM 84 the holotype of a new species, Diplodocus carnegii, with the smaller CM 94 becoming the paratype. In his description Hatcher also provided the first full-body reconstruction of a Diplodocus skeleton. Apart from being quite low-slung, its tail is also notably shorter than we are used to nowadays, in many ways resembling Marsh’s earlier restorations of Brontosaurus.

Fig. 9.

This was quickly revised again in 1905 with Holland’s redescription for the museum mount, where Diplodocus finally got its characteristic long whiptail. Quickly, Diplodocus became not only an animal with a unique appearance, but also a record-breaker, as it was the longest dinosaur, let alone land animal, known up to that point.


Fig. 10

Holland’s paper was accompanied by this life reconstruction, possibly the first ever of Diplodocus, by Alice B. Woodward. It apparently had appeared earlier that same year in a May 13th issue of the Londoner magazine Weekly Graphic (Holland 1905). It likely also served as a base for a later image by Woodward appearing in Nebula to Man, by Henry Robert Knipe. It is an interesting reconstruction. While the animal is depicted as low-slung and probably rather sluggish, it is a lot leaner than many later depictions. The clawed, turtle-like feet are also closer to the real animal than in later reconstructions, which tended to give sauropods very simplified elephant-feet.

Fig. 11

Other life reconstructions where soon to follow, such as this famous painting by Charles R. Knight, made under the direction of Henry Fairfield Osborn for the American Museum of Natural History. It is notable that this reconstruction is somewhat at odds with Osborn’s own vision of sauropod lifestyles, as he was very much of the opinion that these animals were mostly water-dwellers, only venturing onto land on occasion (Desmond 1975, Hallet & Wedel 2016). The behaviour depicted here, standing on land proudly erected onto the hindlegs, is therefore more of a rare occurrence, meant to impress the museum-goers. The second individual on the right, doing its best Nessie-impression, seems deliberately tacked on to remind the viewer of how this animal is normally supposed to live. Ironically, the one on the left aged far better, as many researchers agree that diplodocids were capable of bipedal rearing, with some even arguing that this was how they most commonly browsed tree-tops (Hallett & Wedel 2016).

Dippy Drama

Fig.12.

Andrew Carnegie was ecstatic at the discovery of D. carnegii, obviously in part because the species was named after him. He was not satisfied with just displaying skeletals on paper, but instead wanted the whole skeleton to be mounted in his museum. Thus was born in 1907 Dippy, which was composed by Holland out of the holotype CM 84 and the smaller CM 94. However, even then the full skeleton could not be fully restored, which is why some minor parts were used from other sauropods. Most notably, the original skull of Dippy was a mold based off the specimen USNM 2673, which is today recognized as actually belonging to a wholly different species, Galeamopus pabsti (Tschopp et al. 2015). Despite this, Dippy was an impressive skeletal mount for the time and even gained international attention. Already in 1902, after having seen early sketches for the upcoming mount, King Edward VII. asked the Carnegie Museum if it is possible to procure another skeleton for the British Museum. The museum complied and sent out another expedition to Sheep Creek, but without luck, as no additional skeletons as good as the two CMs could be found. William Holland then had the brilliant idea of just copying the Dippy they already had by making plaster molds of every bone, which could then be shipped and reassembled overseas. And this is exactly what they did. The museum in fact made multiple copies of Dippy and shipped them not just to London, but also, in an act of philanthropy, to the natural history museums of Berlin, München, Paris, Wien, Bologna, St. Petersburg, La Plata, Madrid and Mexico City. Most of the shipments were accompanied by Holland himself, who supervised their assembly. The shipments became a Europe-wide media-sensation, Dippy quickly became the centrepiece of many museums and Diplodocus one of the household dinosaur names. According to some sources (Russell 1988), in French Diplodocus has become a generic term for sauropod, much like “brontosaur” in English. I have no way of confirming this, since I principally refuse to speak to French people.

Fig. 13.

Not everyone was happy with Dippy’s world-tour. Already in 1905 during the unveiling of London’s Dippy, a certain F. W. Frohawk asked the Carnegie workers if they were certain about the pillar-erect limb position that they reconstructed the dinosaur’s legs in. Possibly spurred by this, one of the paleontologists working for the Carnegie Institute, Oliver Perry Hay, actually dissented with the erect posture of the Dippy mounts. He argued that Hatcher and Holland had gotten it wrong by assuming that a cold-blooded reptile of this size would walk with upright elephantine legs like a mammal. Instead he thought that the dinosaur would have walked with sprawled legs like a modern lizard or crocodile, allowing it to rest most of its weight on the ground.

Fig. 14.

German paleontologist Gustav Tornier even drew a skeletal based off Hay’s proposal, which very likely served as the basis for the infamous life reconstruction by Heinrich Harder above. This whole idea did not survive the 1910s, for obvious reasons. Holland (1910) wrote a lengthy rebuttal to Hay’s and Tornier’s criticisms, finding a very critical flaw in them: Not only would all the limbs have been painfully disarticulated in such a position, the animal’s ribcage was deeper than the shoulders (something omitted in Tornier’s skeletal), meaning that if it had actually crawled with sprawled-out legs, the chest would have hung deeper into the ground than the feet, meaning it could have only been able to move forward if its belly was constantly hanging into a WW1-style trench.

This is just the beginning of the story. There is much, much more to write about the history of Diplodocus, which is why I decided to split this up into two parts. Next time we will look at the transformation of Diplodocus from a sluggish swamp monster into a “giraffosaur” and also look at some of the weird and controversial questions which have been asked about it. What did it eat? Did it have a trunk? Could it give live birth? How did it hold its neck? Do we actually know less about Diplodocus than previously assumed? Tune in next time to find out what people have thought in the past and present.

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Related Posts:

Online Sources/Further Reading:

References:

  • Augusta, Josef: Tiere der Urzeit, Prag 1956.
  • Bakker, Robert Thomas: The Dinosaur Heresies. New Theories Unlocking The Mystery of the Dinosaurs and Their Extinction, New York 1986.
  • Ballou, W. H.: Strange creatures of the past, in: The Century Illustrated Monthly Magazine, New York, 55, 1897, S. 15 -23.
  • Colbert, Edwin: Men and Dinosaurs, London 1968.
  • Coombs, Walter: Sauropod habits and habitats, in: Palaeogeography, Palaeoclimatology, Palaeoecology 17, 1975, p. 1-33.
  • Desmond, Adrian: The Hot-Blooded Dinosaurs. A revolution in Paleontology, London 1975.
  • Flammarion, Nicholas Camille: Le monde avant la création de l'homme: origines de la terre, origines de la vie, origines de l'humanité, Paris 1886.
  • Gilmore, Charles Whitney: On a newly mounted skeleton of Diplodocus in the United States National Museum, in: Proceedings of the United States National Museum, 81, 1932, S. 1–21.
  • Hallett, Mark/Wedel, Mathew: The Sauropod Dinosaurs. Life in the Age of Giants, Baltimore 2016.
  • Hatcher, John Bell: Diplodocus Marsh, its osteology, taxonomy and probable habits, with a restoration of the skeleton, in: Mem. Carnegie Mus., 1, 1901, S. 1 – 63.
  • Hay, O. P., 1908. On the habits and the pose of sauropodous dinosaurs, especially of Diplodocus, Am. Nat., 42, pp. 672-881.
  • Holland, William Jacob: The osteology of Diplodocus Marsh with a special reference to the restoration of the skeleton of Diplodocus carnegiei Hatcher presented by Mr. Andrew Carnegie to the British Museum, in: Mem. Carnegie Mus., 2, 1905, S. 225 – 264.
  • Holland, William Jacob: A review of some recent criticisms of the restoration of sauropod dinosaurs, with special reference to that of Diplodocus carnegiei in the Carnegie Museum, in: Am. Nat., 44, 1910, S. 259 – 283.
  • Holland, William Jacob: The Skull of Diplodocus, in: Mem. Carnegie Mus., 9, 1924, S. 379 - 404.
  • Marsh, Othniel Charles: The Dinosaurs of North America, in: Annual Report of the US Geological Survey, 16, 1896, S. 135 - 415.
  • Martin et al.: Not cranes or masts, but beams: The biomechanics of sauropod necks, in: Oryctos, 1, 1998, S. 113 – 120.
  • Matthew, William Diller: Dinosaurs. With special reference to the American Museum collections, New York 1915.
  • Mcloughlin, John: Archosauria. A New Look at the Old Dinosaur, New York 1979.
  • Osborn, H. F., and C. C. Mook. 1921. Camarasaurus, Amphicoelias and other sauropods of Cope. Memoirs of the American Museum of Natural History, n.s. 3:247-387 and plates LX-LXXXV.
  • Osborn, Henry Fairfield: Cope. Master Naturalist, Princeton 1931.
  • Popular Science Monthly, Vol. 72, 1908, S. 440.
  • Probst, Ernst: Tiere der Urwelt. Leben und Werk des Berliner Malers Heinrich Harder, Norderstedt 2014.
  • Russell, Dale: An Odyssey in Time. The Dinosaurs of North America, Minocqua 1988.
  • Taylor et al.: The long necks of sauropods did not evolve primarily through sexual selection, in: Journal of Zoology, 824, 2011, S. 1 – 12.
  • Tschopp, Emanuel/Mateus, Octavio/Benson, Roger: A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda), in: PeerJ, 3, 2015.
  • Wells, Herbert George: A Short History of the World, London 1922.
  • Witmer, Lawrence: Nostril Position in Dinosaurs and Other Vertebrates and Its Significance for Nasal Function, in: Science, 293, 2001, 850 – 853.

Image Sources:

  • Fig. 1: McLoughlin 1979.
  • Fig. 2: Osborn & Mook 1921.
  • Fig. 3: Flammarion 1886.
  • Fig. 4: Marsh 1896.
  • Fig. 5: Ballou 1897.
  • Fig. 6: Wikimedia
  • Fig. 7: Marsh 1896.
  • Fig. 8: Hatcher 1901.
  • Fig. 9: Holland 1905.
  • Fig. 10: Holland 1905.
  • Fig. 11: Wikimedia
  • Fig. 12: Popular Science Monthly, Vol. 72, 1908, S. 440.
  • Fig. 13: Hay 1908.
  • Fig. 14: Probst 2014.

Saturday, 25 June 2022

Stegosaurus: A history of reconstructions

A likely reason for what makes dinosaurs so appealing to us today is that they combine the familiar with the unfamiliar. We can see attributes of giraffes, rhinos, turtles or birds in sauropods, ceratopsians, ankylosaurs and theropods, recombined in ways that feel both alien yet still understandable. However, there is at least one group of dinosaurs that one can describe as truly alien with no modern analogues and those are the stegosaurs. A bird-like tiny head sits on a long neck attached to a massive body, with almost comically disproportionate limbs and a tail that looks more like a medieval weapon than a biological structure. And then there is of course the famous, strangely arrayed backplates and spikes, the likes of which, to paraphrase John Foster, can arguably only be found elsewhere in the lobopods of the Cambrian. The true strangeness of Stegosaurus and its close relatives is something that can be underappreciated at times and nowhere else is this as apparent as when looking back at the history of people trying to piece this animal back together. In many ways, the history of reconstruction of this genus might be a good test case for what might happen one day should mankind ever try to reconstruct multicellular fossils on another planet like Mars.

The earliest years with Stegosaurus armatus

The first known remains of a Stegosaurus (YPM 1850) were described by Othniel Charles Marsh in 1877, during the midst of the infamous Bone Wars. The material, uncovered by Arthur Lakes north of the town of Morrison in Colorado, was highly incomplete, mostly consisting of a few vertebrae, other postcranial bones and a single of the famous dorsal plates. There were also teeth and limb bones assigned to the specimen, but these later turned out to have actually belonged to a Diplodocus and an Allosaurus respectively (Carpenter & Galton 2001). Despite the incompleteness, YPM 1850 was still assigned to be the holotype of a new dinosaur species, Stegosaurus armatus, because Marsh was Marsh and the Bone Wars were the Bone Wars. The genus name Stegosaurus means “roofed lizard” and derives from Marsh’s initial interpretation of the animal. He believed that the backplates of the animal were similar to those of the Cretaceous stem-turtle Atlantochelys and thus interpreted them as lying flat on the back like roof-tiles to form a carapace (Marsh 1877). What later turned out to be tail-spikes were also initially interpreted as part of the dorsal armor, perhaps sticking out between the plates. Marsh’s initial vision of the animal was a sort of turtle-like dinosaur that lived mostly in water, but when coming out on land would walk bipedally. The latter idea derives in part from the disproportionate length of the limbs (though mind you some of these came from an Allosaurus, as mentioned), but also because it was commonly thought between the 1860s and the 1870s that all dinosaurs were bipeds, as the most complete dinosaur skeletons up to that point were those of Hadrosaurus and Dryptosaurus (Laelaps). Only in the same year as Marsh’s description was it made apparent that some dinosaurs were indeed quadrupeds, when Edward Drinker Cope sketched the first skeletal for Camarasaurus.

Fig. 1

Marsh provided no restoration for YPM 1850. The first known artistic depiction of Stegosaurus instead appeared in the 51st issue of the Scientific American, on the 29th November of 1884. The illustration was made by a certain A. Tobin, whose full name and further information I have unfortunately never been able to uncover. The article the above illustration appeared in was not about Stegosaurus specifically, but about dinosaurs in general and advances in paleontology, as such there is not much information behind the reconstruction and the purpose of the image was simply to show readers of the time what dinosaurs were like in the flesh. Tobin seems to have based it roughly on Marsh’s initial description, though still has taken some liberties. The dinosaur is presented less turtle-like and instead fairly lean, with an outline and posture more typical of other dinosaur depictions at the time. This is very apparent thanks to the other dinosaur standing behind it (which the description in the article identifies as Compsognathus, which is very strange, as not only were the two genera geographically separated from each other, but Compsognathus was only about the size of a chicken). What is notable and perhaps prescient about Tobin’s depiction is that it shows at least some of the plates sticking out of the skin instead of lying flat on top. Though this may also be coincidental to create a tail similar to that of a crocodilian.

Of Ungulatus, Stenops and the first skeletal

Even before Tobin, Marsh got busy with his stegosaurs. In 1879 already, Lakes found for him several more stegosaur fossils in the famous Como Bluff. Among them was YPM 1853, which was the holotype for the new species Stegosaurus ungulatus. It was a lot more complete than the previous specimen, preserving parts of the skull, many of the vertebrae, limb bones, backplates and tail spikes. In the following years Marsh went on to describe two further species, S. affinis and S. duplex, but these were based off specimens that were either too simple to deserve distinction or are lost today. A breakthrough was made in 1885, when Marshall P. Felch uncovered USNM 4934 at the Garden Park quarry in Colorado. The stegosaur was not only very complete, but fully articulated. This made it the best glimpse into the true anatomy of Stegosaurus up to that point. Based off it, Marsh described it as the new species Stegosaurus stenops in 1877. On a side note, another species was named by him the same year with Stegosaurus sulcatus, based off USNM V 4937. S. sulcatus is rarely talked about but still notable, as it is probably still valid and possibly the only Stegosaurus species that possessed shoulder-spikes similar to other stegosaurs like Kentrosaurus (Galton 2010).

Fig. 2.

Based on all this new information, Marsh published the very first full skeletal of a Stegosaurus in 1891, which you can see above. This is likely also the most well-known illustration of the animal, as it has been reproduced in art and books too many times to count. Despite its prominence, there are many particularities about it that often go uncommented. Firstly, instead off basing it off the skeleton of the largely complete S. stenops, Marsh tried to depict the more incomplete S. ungulatus with this skeletal, filling in blank areas with data from S. stenops and other Stegosaurus. Therefore, this skeletal is a composite of many specimens, which as we will see, would have some grave consequences down the line. Secondly, there is the arrangement of the famous backplates. Marsh had by now realized that they did not lie flat, but instead grew erect out of the skin, as the attachment sites for the skin and flesh were only at one end of the plate instead of one whole surface. However, the way he imagined them to be patterned differed strongly from our modern vision. Marsh interpreted the plates to all grow behind each other in a single line along the spine. Possibly, this is what forced the dinosaur into such a dramatically arched position, as otherwise Marsh could not have fit on all the plates on the back. There is a chance some of you might still be familiar with this arrangement, as Stephen Czerkas briefly tried to revive this idea in 1987, using the arrangement of spikes on modern lizards like iguanas as an argument. While in scientific circles this never went anywhere, Czerkas’ single-plate-line model was still popular enough to become the basis for the Stegosaurus toy in the very first Kenner toyline for 1993’s Jurassic Park (when the dinosaur finally appeared in the movie’s sequel, it thankfully sported the more conventional plate arrangement, but still came with many other problems, including being twice as large as the real animal). Lastly, there is the number of spikes on the tail, which is eight instead of the conventional four. Marsh curiously knew that S. stenops only had four spikes, but thought S. ungulatus had more, as he found up to nine of them with the S. ungulatus holotype. Because the skeleton was mixed together with multiple individuals, Marsh did consider that the spikes were from two or more different tails, but concluded that eight came from a single individual, because his analysis did not consider them to be duplicates (Carpenter & Galton 2001).


Fig. 3.

While quite strange from a modern perspective, Marsh’s first skeletal reconstruction would have a wide-reaching effect. One of them was that it would form the basis for the actual mount of S. ungulatus at the Yale Peabody Museum, which was likewise constructed of multiple individuals. While Richard Swann Lull modified the mount in 1924 to make the plates paired, it did bear eight tail spikes for the majority of its history. The popularity of this skeleton is therefore likely one of the largest reasons why the idea persisted for so long that S. ungulatus can be distinguished from S. stenops by having eight instead of four tail spikes. Today it is thought that Marsh made a mistake in his assumptions and that S. ungulatus really did only four spikes like its relative (Carpenter & Galton 2001). It is still neat to know this bit of history, as it means that any time you see a Stegosaurus with eight spikes in old paleoart, it is most likely meant to depict S. ungulatus. Another long-lived legacy of Marsh’s comes from his 1896 monograph The Dinosaurs of North America, in which he emphasizes the nervous system (or rather lack thereof) in Stegosaurus. While Marsh never actually did claim that the hollow cavity in the hip vertebrae was the resting place of a second brain, he suggestively talks about it in strong relation to the small size of the skull’s brain cavity. It was therefore very easy to simplify Marsh’s writing as claiming that Stegosaurus had such a small brain in its skull that it needed multiple nerve centers to operate different parts of the body. Thus was born the unfortunate myth of the butt-brained dinosaur. Today it is thought that the hip-cavity instead housed a glycogen reserve, as it very much still does in some modern birds.

Fig. 4.

Marsh’s work was shortly thereafter followed by the first life reconstruction of the “new” Stegosaurus with a single plate-line and eight tail-spikes, appearing in the popular book Extinct Monsters from 1893, by H.N. Hutchinson, illustrated by Dutch zoology illustrator Joseph Smit. Differing from Marsh’s skeletal, which had more elephantine limbs, the animal is presented here crawling almost like a lizard or a crocodile and indeed many reconstructions from the late 19th century, such as those of Heinrich Harder, would emphasize the reptilian nature of the animal with such postures. In part, this may have been due to the growing dogma at the time about dinosaurs as a whole being just overgrown lizards, though one can also imagine that this was done in part to also make this almost alien creature seem more familiar.

Fig. 5

A strange intermezzo from the general trend appeared in 1899, with this illustration by Frank Bond under the guidance of a certain W.C. Knight from the University of Wyoming (Gilmore 1914). While the general outline of the body seems to have taken notice of Marsh’s skeletal, the arrangement of the armour is a genuine throwback to his original idea from 1877 of a “turtlesaur”, making this illustration pretty anachronistic. Ironically, it also shows the animal to be more flexible and dynamic than usual at the time and it would take over half a century before someone would consider again the possibility of Stegosaurus being able to rear up on its hindlegs.

Fig. 6

1901 saw perhaps the most classic of the old depictions of the animal, drawn by none other than Charles R. Knight, though under the guidance of Frederic Lucas, at the time a curator for the Smithsonian Institution (Gilmore 1914). Lucas commissioned the painting to portray his new idea that the plates of Stegosaurus were not all aligned in a single line, but instead grew in pairs. Unlike modern depictions, he and Knight thought them to have been arranged in bilateral symmetry, meaning the plates mirrored each other. To give credit where credit is due, most people would probably agree that this was the more intuitive interpretation than what we ended up with today. Long into the early 20th century, Richard Swann Lull would still defend the paired-plate model and, as mentioned, would have the Yale mount display it. A few other notable things about Knight’s first reconstruction are how dark and menacing he drew the animal and how he gave it a hooked beak, something not apparent in the real animal’s skull (which, I personally think, when viewed up close, has actually more of a resemblance to early ornithopod skulls, like Camptosaurus). Despite this, portraying Stegosaurus with an almost eagle-like head would become a minor paleoart trope, appearing most prominently in the first illustrated version of Arthur Conan Doyle’s The Lost World.

Fig. 7.

Less than a year after Knight’s painting, Lucas already revised his model and instead concluded that the plates of Stegosaurus were arranged in an alternating/glide-symmetric pattern (Gilmore 1914), meaning they did not mirror each other but instead formed a distinct left and right side. The main reason for this is that the plates are actually arranged this way in the type specimen of Stegosaurus stenops (which is why the dinosaur here only has four tail spikes). This is also the reason for why this reconstruction remains the dominant one today. While it has been argued that the alternating pattern could be an artefact of taphonomy, the completeness and articulation of the skeleton argues against this and other specimens also show signs of such chirality (Cameron et al. 2016). In the same year of 1901, Lucas commissioned a drawing of this new hypothesis from a certain G.E. Roberts, which is most likely the very first depiction of Stegosaurus in art with an alternating plate-arrangement (Gilmore 1914). Unfortunately, the drawing here is not very good, especially anatomy-wise, and was not widely publicized at the time, only appearing years later, in 1910, in an article for the magazine Outdoor Life (Gilmore 1914).

Fig. 8 & 9.

Thankfully, Lucas commissioned Knight again in 1903 to recreate Roberts’ version, but with a more robust anatomy (Gilmore 1919). This time it was in the form of a miniature wax model. Knight would use this as a basis for a gigantic life-sized model of S. stenops, which was originally produced for and exhibited in the World’s Fair of St. Louis of 1904 (Gilmore 1919). Its exhibition at said World’s Fair is possibly one of the reasons why the alternating plate-model was also the one that became more prominent with the wider public than any other interpretation. After the fair, the model would go to the United States National Museum, where it would accompany the S. stenops skeleton USNM 6531. As I have never been to that museum, I do not know what happened to this model. If you know more about its whereabouts, please tell.

Edit: As a friendly commenter has informed me, "Steggy the Stegosaurus" has thankfully survived to modern day, but has been transferred from the Smithsonian to the Museum of the Earth, in Ithaca, New York State. Thank you Abel Alfonso for this info!

Fig. 10.

In 1915, Charles Whitney Gilmore, who has been a great resource on the early history of Stegosaurus, would create his own little life model of the critter.  It is similar to Knight’s, albeit more gracile and compact.

Fig. 11.

Unfortunately for Gilmore, the only time his model would be referenced was in a newspaper article of the Ogden Standard-Examiner from the 15th of August 1920 (which is NOT April Fools day). Written by a man named W.H. Ballou, who had previously worked as an illustrator for Edward Drinker Cope, the article titled “The Aeroplane Dinosaur of a Million Years ago” seriously proposes that Stegosaurus was capable of not only flexing its backplates, but also using them to glide though the air! How Ballou came to such a conclusion is hard to discern, though the notion that birds descended from dinosaurs was still en vogue at this time and Ballou emphasizes the fact that Stegosaurus was part of the Ornithischia, the bird-hipped dinosaurs. While we today know that birds actually descend from the Saurischia, Ballou obviously did think that there is a close connection (as did others before him) and could therefore have very well concluded that some members of the group could have also experimented with other forms of flight. While obviously ridiculous, the idea did curiously reappear again in 1930 in the novel Tarzan at the Earth’s Core by Edgar Rice Burroughs. Yes, THE Tarzan gets attacked by such “aeroplane dinosaurs” in this story. As far as I know, it is not known if Burroughs actually did read this fairly obscure newspaper article or separately came up with the concept by himself.

The classic years

Fig. 12.

Stegosaurus appeared again in spectacular fashion (and thankfully on the ground) in 1933’s classic King Kong, brought to life by Willis O’Brien in glorious stop-motion. The dinosaur is the first prehistoric animal that the protagonists meet on the island and not only is it presented as larger than life, but also requires a multitude of rifle shots to be brought down. It is notably the last prominent depiction to show the plates being arranged in pairs and likely was based off Knight’s first reconstruction. Instead of a beak it also seems to sport scaly lips. People forgetting that Stegosaurus had a beak of some kind is strangely prevalent in some pop-culture-depictions, with even the Jurassic World movies making this error (made doubly strange with the older The Lost World: Jurassic Park actually getting this detail right). One could speculate that this is intentionally done to make the animal more reptilian (and therefore probably monstrous), as beaks are something associated more with birds, but then again, turtles have beaks too. A genuine lack of even the most basic research might therefore be the more likely reason.

Fig. 13.

1940 saw the next prominent appearance of Stegosaurus in film with Walt Disney’s Fantasia, which I have already written about. As is typical, the animal is presented as downright lardy and ponderous when in a peaceful mood. Notably though, when locked in a fight against a T. rex (which yes, is very anachronistic), the dinosaur is shown being mobile and prominently uses its tail as a defensive weapon. As far as I am aware, this scene is indeed the first time that Stegosaurus is shown using its weapon in this fashion in any sort of media. This was in fact the reason why Stegosaurus was used in this scene over Triceratops (who was originally planned for it) because the animators were very excited at the opportunity of finally showing this dinosaur using its natural weapons in the way scientists thought it did at the time (Culhane 1983). One has to keep in mind that the Rite of Spring segment of Fantasia was also meant to be partially educational, at a time long before actual dinosaur documentaries as we know them existed.

Fig. 14.

Excluding such highlights, the general view of Stegosaurus from the 30s until the early 70s was as the quintessential embodiment of everything “wrong” with dinosaurs, as we can see here on the famous Zallinger mural from 1947: a large mass of fat, muscle and armour, with barely a brain to control this bulk. Due to the disproportion of the dinosaur’s limbs, it was usually interpreted as a very awkward walker, with erect hindlegs and sprawled forelimbs, which made the whole front-portion of the dinosaur low-slung. Together with the bizarre armour and notions of phylogeronty (the idea that groups of animals could age like an individual person and, when too long-lived, degenerate), Stegosaurus was interpreted as a misshapen creature whose evolution had clearly invested in the wrong traits and was then left directionless, destined for extinction.

Fig. 15.

A related view can be seen in the 50s with Czech paleontologist Josef Augusta’s writings, wherein stegosaurs are described “like living, impassable fortresses, like armored battle vehicles of primevally wonderful construction […]” (Augusta 1957). Living in the Cold War environment behind the Iron Curtain, Augusta seems to have been interested in the combative nature of the dinosaur. That this militaristic description is immediately followed by Augusta perpetuating the myth of Stegosaurus being so stupid that it needed two brains, paints this interest, however, in a less glorifying light and might instead be viewed as social commentary on the political environment at the time. This view of Stegosaurus, a beast that invests too much in weaponry and is too stupid to even consider other options (and is thus destined to fail), could easily be interpreted as a caricature of the Soviet Union, the United States or even both at the time. The images accompanying Augusta’s descriptions, made by none other than Zdeněk Burian of course, are largely typical of the time. Unlike most artists before him, though, Burian did pay a lot of attention to the fossil skull, even if, like with Knight, the reconstruction ended up a bit too birdlike. As Zoe Lescaze (2017) notes, depicting the dinosaur from behind was also a bold and unusual decision at the time that showcases how confident Burian felt in his skills.

Growing appreciation and some experimentation

 

Fig. 16.

With the beginning of the 70s also began what we all know as the Dinosaur Renaissance. Renewed fascination and appreciation for the terrible lizards made many researchers reconsider their preconceived notions and this not only led to dinosaurs being seen more as successful, metabolically active creatures, but also gave rise to many quite unorthodox hypotheses about dinosaur anatomy, behaviour and lifestyles. While Stegosaurus continued to be depicted as a rather ponderous animal even during the early years of the Renaissance, its weird features were already subject to new interpretations. The obvious point of contention were again the backplates and the question if and how they could have been used as defence. One of the first of such reinterpretations came in 1975 from a popular book by Beverly Halstead, illustrated by Giovanni Caselli. Halstead not only reverts the arrangement of the plates back to a bilateral one, but also opines that they stuck out to the sides like wings, as he thought that in this position they would act a lot better to deter predators. This idea never caught on, as in this position, there would likely not have been enough muscle- and ligament-support to hold the plates in such a fashion and any theropod smart and agile enough would have probably been able to simply bite the animal’s flanks underneath the armor. To give credit where credit is due, Halstead was also of the opinion that the front legs of Stegosaurus would have been held erect like pillars, instead of bent like in earlier reconstructions, as this makes the most structural sense for such a heavy animal. This idea would go on to become consensus.

Fig. 17.

A year later, Ronald Raul Ratkevich and his illustrator, the one and only John C. McLoughlin, presented an interesting behavioural hypothesis. While keeping the erect and chiral arrangement of the plates, they thought that Stegosaurus defended itself by rolling up into a defensive wheel, the plated back thus forming a spiked wall. This has also never caught on, as theropods would have probably been smart enough to approach the stegowheel from a convenient angle and bite right in the unprotected center. An interesting detail regarding this reconstruction is that, as far as I am aware, it is the only one that also shows the spikes on the tail as being arranged with glide-symmetry. While an interesting thought, this does not seem to have been the case in reality. Another interesting detail is that this is possibly the first reconstruction since Frank Bond’s from 1899 that depicts Stegosaurus as being capable of rearing up bipedally.

Fig. 18.

It would be a disservice to not mention an unusual, though rather influential event in stegosaur research, which is Gary Larson publishing this little comic in 1982. Although merely a silly joke, ever since Kenneth Carpenter used it in a 1993 lecture, the term “thagomizer” has actually become a regular name used by many paleontologists for the tail weapons of stegosaurs and even some other dinosaurs. The bones they work with may be dry, but their humour certainly is not.

Fig. 19.

Not everyone was on board with the Dinosaur Renaissance and especially in popular books older ideas and traditions of illustrations persisted, as showcased by this spread from 1985’s The Illustrated Encyclopedia of Dinosaurs by David Norman. As is pretty obvious, Norman’s skeletal here is basically the same as the one Marsh drew in 1891, just with the plates updated. Despite its often anachronistic nature, the “Normanpedia” would nevertheless go on to be quite popular and influential among younger readers, thanks to John Sibbick’s colorful life reconstructions. Thus the vision of ponderous Stegosaurus still lived in on in the popular mind.



Fig. 20.

The next year saw the landmark release of Robert Bakker’s The Dinosaur Heresies, where Bakker gave the animal the full Renaissance treatment. Bakker insisted, like Halstead, that Stegosaurus walked with erect front legs, but also that the animal’s shoulder bones could move independently from the ribcage, as in mammals, giving it more flexibility and making it a more efficient quadruped. Bakker furthermore reinforced the idea that Stegosaurus actively used its tail as a weapon, as the tail, unlike in other ornithischians, lacked ossified tendons, giving it far greater flexibility. The mismatch in length between the hind and front limbs also gave the animal a great ability to quickly circle its behind in the direction of an attacker. These are all ideas still very much supported today (in part because we have actually found thagomizer-spikes deeply imbedded in the bones of allosaurs). However, Bakker also had some ideas that still seem unorthodox today. I already wrote about his hypothesis that stegosaurs regularly reared up on two legs to browse on tall plants. Stegosaurs being facultative bipeds is actually supported today by trace fossils called Garbina from Early Cretaceous Australia (Salisbury et al. 2016). Another interesting idea of Bakker’s, unintentionally echoing Ballou, was that the dinosaur could independently move its plates into a defensive position when threatened thanks to muscles attached at the bases. Although once prominently featured in a popular 90s documentary, this has also never caught on, likely because there is not much evidence for such muscle attachments.

Fig. 21.

The end-point of the Renaissance-era developments could perhaps be represented by this skeletal from 2010 by Gregory S. Paul. While the weirder ideas from the 70s and 80s have not persisted, the dinosaur has still undergone many updates compared to older reconstructions. The tail and head are now held clearly above the ground and the dinosaur strides on erect legs. Paul also bothered to include the fact that Stegosaurus actually had throat armour made of smaller ossicles, something actually known since the discovery of the S. stenops type specimen. Paul has also covered the plates in keratin sheaths, something which was confirmed by skin impressions from close relative Hesperosaurus (Christiansen & Tschopp). In general, it was however still a bizarrely proportioned animal, which was soon about to change.

New girl, new times

Fig. 22.

Since Marsh’s first description of the order Stegosauria, many new species related to Stegosaurus had been found all around the world, such as Kentrosaurus, Dacentrurus, Huayangosaurus, Miragaia, Hesperosaurus and the deceptively named Gigantspinosaurus. These revealed a rather surprising thing, which was that the genus Stegosaurus, despite giving the whole group its name, was actually a quite unusual stegosaur. Most other stegosaurs did not have a such dramatic limb proportions, had dorsal spikes in addition to plates, prominent shoulder-spikes, long necks and in general long-stretched bodies. One thing that someone had to consider, however, was that up until the 2010s nearly all skeletals of Stegosaurus, including the one by Paul from before, were composites of multiple individuals, as most specimens were either not completely preserved or were hard to access for such skeletal reconstructions. The last complete description of the genus was also all the way back in 1914 by Charles Gilmore. This all changed in 2015 with the description of “Sophie” (SMA RCR0603/ NHMUK PV R36730), a specimen of Stegosaurus stenops. Sophie was originally discovered in 2003 in the Red Canyon Quarry and excavated by the team from the Swiss Sauriermuseum. Sophie is the most complete Stegosaurus skeleton known to date and has given many new insights into the actual anatomy of the genus. Most importantly, the skeleton shows that Stegosaurus was not actually all that different from other stegosaurs, as we can see here in Scott Hartman’s skeletal from 2016, based on Sophie. The difference in length between the limbs is not as pronounced as was once assumed, the spine is more evenly horizontal, the chest is shallower and the neck is longer. Though more similar now to its brethren, Stegosaurus still has some unique traits, such as the lack of shoulder spikes (except for S. sulcatus) and the plates running all the way from the head to the tail tip. It also remains the largest member of the Stegosauria.

This is highly unlikely to have been the last chapter of Stegosaurus’ history. The only constant, not just in nature but also science, is change, and there still remain many questions regarding this peculiar creature from so long ago, more removed in time from Tyrannosaurus rex than is humanity. Were the plates just there for display or were they really used in defence? Did Stegosaurus eat from tall plants or was it a low browser? Did it have a low bite force and only ate the softest plant parts or had it a tougher diet? Is the gradual extinction of stegosaurs linked to sinking cycad-populations? Did some stegosaurs survive in India until the End Cretaceous? What were its facial tissues like? Did the beak extend all around the rims of the jaw or did it have lips and cheeks? What colours did it have? Did it care for its young or live in herds? How did it interact with other herbivorous dinosaurs? Is the small size of the brain really indicative of exceptionally low intelligence? How many Stegosaurus species are there really? These are all questions that remain open or are at the very least highly debated. Some may be answered in the future, some may be not. What is sure is that Stegosaurus is and will remain an icon of fascination, even in the (highly improbable but not impossible) case that Hartman's reconstruction will one day be as ridiculed as Tobin's is today.

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References:

  • Augusta, Josef: Tiere der Urzeit, Prag 1956.
  • Augusta, Josef: Verwehtes Leben, Prag 1957 (Deutsche Übersetzung von Max Schönwälder).
  • Bakker, Robert Thomas: The Dinosaur Heresies. New Theories Unlocking The Mystery of the Dinosaurs and Their Extinction, New York 1986.
  • Ballou, W. H.: Strange creatures of the past, in: The Century Illustrated Monthly Magazine, New York, 55, 1897, S. 15 -23.
  • Ballou, W.H.: The Aeroplane Dinosaur of a Million Years ago, in: The Ogden Standard-Examiner, 15. August 1920, S. 8.
  • Cameron, R. P; Cameron, J. A; Barnett, S. M.: Stegosaurus chirality, 2016.
  • Carpenter, Kenneth & Galton, Peter: Othniel Charles Marsh and the Myth of the Eight-Spiked Stegosaurus, in: Carpenter, Kenneth (Hg.): The Armored Dinosaurs. Bloomington 2001, S. 76–102
  • Christiansen, Nicolai/Tschopp, Emanuel: Exceptional stegosaur integument impressions from theUpper Jurassic Morrison Formation of Wyoming, in: Swiss Journal of Geosciences, 103, 2010, p. 163- 171.
  • Culhane, John: Walt Disney's Fantasia, New York 1983.
  • Czerkas, Stephen: A Reevaluation of the Plate Arrangement on Stegosaurus stenops, in: In Czerkas/Olson (Eds.): Dinosaurs Past & Present, 2, 1987, Seattle. p. 82–99
  • Galton, Peter: Species of plated dinosaur Stegosaurus (Morrison Formation, Late Jurassic of western USA: New type species designation needed, in: Swiss Journal of Geosciences, 103, 2010, p. 187 – 198.
  • Gilmore, Charles Whitney: Osteology of the armored Dinosauria in the United States National Museum, with special reference to the genus Stegosaurus, in: Smithsonian Institution United Stated National Museum Bulletin, 89, 1914.
  • Gilmore, Charles Whitney: A newly mounted skeleton of the armored dinosaur Stegosaurus stenops in the United States National Museum, in: Proceedings U. S. National Museum, 54, 1919.
  • Halstead, Beverly: The Evolution and Ecology of the Dinosaurs, Somerset 1975.
  • Lescaze, Zoe: Paleoart. Visions of the Prehistoric Past, Köln 2017.
  • Maidment, Susannah Catherine Rose; Brassey, Charlotte; Barrett, Paul Michael: The Postcranial Skeleton of an Exceptionally Complete Individual of the Plated Dinosaur Stegosaurus stenops (Dinosauria: Thyreophora) from the Upper Jurassic Morrison Formation of Wyoming, U.S.A., in: PLoS One. 2015.
  • Marsh, Othniel Charles: A new order of extinct Reptilia (Stegosauria) from the Jurassic of the Rocky Mountains, in: American Journal of Science, 3, 1877, p. 513 – 514.
  • Marsh, Othniel Charles: Restoration of Stegosaurus, in: American Journal of Science, 3, 1891, S. 179–81.
  • Marsh, Othniel Charles: The Dinosaurs of North America, in: Annual Report of the US Geological Survey, 16, 1896, S. 135 - 415.
  • Paul, Gregory Scott: The Princeton Field Guide to Dinosaurs, Princeton 2010 (2. Edition 2016).
  • Ratkevich, Ronald Raul: Dinosaurs of the Southwest, Albuquerque 1976, S. 56.
  • Revan, Ariel: Reconstructing an Icon. Historical Significance of the Peabody’s Mounted Skeleton of Stegosaurus and the Changes Necessary to Make It Correct Anatomically. (Bachelorarbeit Yale University, 2011).
  • Salisbury, Steven; Romilio, Anthony; Herne, Matthew; Tucker, Ryan; Nair, Jay: The Dinosaurian Ichnofauna of the Lower Cretaceous (Valangian-Barremian) Broome Sandstone of the Walmadany Area (James Price Point), Dampier Peninsula, Western Australia, in: Journal of Vertebrate Paleontology, 36, 2016, p. 1 – 152.
  • Volpe, Rosemary: The Age of Reptiles. The Art and Science of Rudolph Zallinger’s Great Dinosaur Mural at Yale, New Haven 2007.

Online Sources/Further Reading:

Image sources:

  • Fig. 1: Dinosaurs, in: Scientific American, 51, 29. November 1884.
  • Fig. 2: Marsh 1891.
  • Fig. 3: Revan 2011.
  • Fig. 4 – 7: Gilmore 1914.
  • Fig. 8 – 10: Gilmore 1919.
  • Fig. 11: Ballou 1920.
  • Fig. 12: King Kong, copyright by RKO Pictures.
  • Fig. 13: Fantasia, copyright by Walt Disney Pictures.
  • Fig. 14: Volpe 2007, foldout.
  • Fig. 15: Augusta 1956.
  • Fig. 16: Halstead 1975, p. 63.
  • Fig. 17: Ratkevich 1976, p. 56.
  • Fig. 18: Wikimedia
  • Fig. 19: Norman 1985, p. 154.
  • Fig. 20: Bakker 1986.
  • Fig. 21: Paul 2010 (2016), p. 249.
  • Fig. 22: Scott Hartman's website