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True to Life?

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Species: aegypticus, moroccanus?
Range: Early Cretaceous (Albian-Turonian , 112-90 MYA) from Egypt, Morocco, Tunisia
Size estimate: 50-60 ft length, 7-9 tons
Discovery: Ernst Stromer, 1915
Classification: dinosauria, saurischia, therapoda, tetanurae, spinosauridae

True to Life?

Since no one has ever seen a living dinosaur, and the missing pieces of the fossil record withhold important clues to their appearance, no artistic representation of a dinosaur ever gets it 100% right. On top of that, new discoveries can change our ideas of extinct creatures drastically. So, how close does this sculpture come to what we know of the original animal?

• The weird dinosaurs get the most artistic versions, especially if they happen to be fragmentary. Spinosaurus is no exception, but it sure proves the rule! About the only thing consistent between different models of Spinosaurus are the presence of a fin and sharp teeth. If you would like to check out a range of different Spinosaurus models, inquire at the Bone Cabin Outpost or ask a docent for more information.
• The depiction you see here is based on the 2014 announcement of the neotype specimen, the first skeleton in about a century with any degree of completeness and by far the best preserved. That said, what’s missing leaves enough questions unanswered to result in a lot of interpretation. That is to say, at the time this model was sculpted, it was based on the best information available. However, the explosion of interest leading from the 2014 study has led to many reinterpretations, revisions, and new discoveries, so even this newer installment of the Dinosaur Park’s menagerie has its drawbacks.
• Most of Spinosaurus’ skull remains unknown, particularly the middle of the snout and eyes. This sculpture takes its cues from the 2014 study, which took Baryonyx as a basis. The skull inside the Stewart Museum follows a different method, using casts from original material to create a composite. Though the 2014 study’s approach uses more solid methodology, it’s interesting to note that at least one other scientist, Tracy Ford, has independently produced a reconstruction quite similar to the skull indoors. We could wish for a complete skull sometime in the future, but given how theropod fossils from North Africa tend to get broken into small fragments, it’s not likely that we’ll be able to resolve this question any time soon.
• Spinosaurus had a longer neck than depicted by the large-scale sculpture. The original maquette for this project portrays it at the correct length, but problems with the engineering of this sculpture’s internal structure made it necessary to shorten the neck so that it would hold up the head properly. By the way, a maquette is a small-scale sculpture used to help translate the artist’s vision to a larger scale. Think of it like a practice piece. Most of the sculptures of the Park have corresponding maquettes.
• If you’ve already read the “True to Life?” article for Baryonyx, you may be anticipating a discussion of Spinosaurus’ posture—that time is now! One of the surprising discoveries to come from the neotype was its short hind legs. Considering its long torso and doing a little preliminary math, the authors of the 2014 study concluded that Spinosaurus’ center of gravity lay well forward of its hips, which would have forced it to adopt a quadrupedal posture. Subsequent studies have recalculated center of gravity based on more data and found Spinosaurus a competent biped. Considering that quadrupedality would not just be unprecedented for a theropod and therefore require an unprecedented level of evidence, but also that several features of the typical theropod forelimb (besides the extreme adaptations birds undertook for powered flight) would require major modifications for such a posture and therefore would most likely have left a series of transitional precedents in the fossil record, the odds are heavily stacked against four-legged Spinosaurus. To name one example of the many problems involved, theropod shoulder joints severely limit forward extension, making them incapable of movement appropriate to a workable gait. Besides the center of gravity calculation, though the 2014 study did refer forelimb material to their model without describing any modifications from known spinosaur forelimbs it may or may not have, it also asserted without argument that all giant spinosaur material from North Africa and the right age of rocks belongs to a single species of Spinosaurus. Considering that a quadrupedal Spinosaurus would have a hard time traveling long distances out of water, that Spinosaurus’ ecological range spanned larger than the continental United States, that Spinosaurus shows no adaptation for dealing with salt water and no geological evidence has been cited in support of a contiguous fresh waterway across its range, the geographical limitation of Spinosaurus populations would encourage speciation. In other words, adding those forelimbs to the Spinosaurus hypodigm—the collection of fossils we consider as informative of the natural species—is not internally consistent with other claims of the model. Therefore, unlike the 2014 model, we posed our sculpture as a biped.
• So much for the scientific rationales given in support of a quadrupedal Spinosaurus. As an artistic trope, Spinosaurus has been crawling much longer than that. Counterintuitively, the reason for the popularity of this trope probably has less to do with its legs and more to do with that sail on its back. Decades before Spinosaurus’ discovery, scientists described fossils of Dimetrodon, Edaphosaurus, and the amphibian Platyhystrix, each of which bears a prominent sail on its back, and each of which is an obligate quadruped—an animal which cannot walk on fewer than four legs. The original holotype of Spinosaurus did not preserve any limb or hip material, but it did preserve its eponymous elongated spines. Confusion with these other fossil animals thanks to their prominent, unusual, and shared spinal features despite a gross difference in size probably led many artists to fill in the missing limbs and hips with a visual reference to these other sailbacks. The Baryonyx “True to Life?” article mentions another reason connected with fishing and grizzly bears—go check it out when you get the chance—and sure enough, as you can see here Spinosaurus’ manual claws also get plenty big, so what got Baryonyx into an improbable crouch helped reinforce the trope in its big, fin-backed cousin.
• Speaking of fins, most prior and a few recent depictions of Spinosaurus restore its fin as a D-shaped structure similar to other fossil sailbacks. The 2014 neotype model found an M-shaped fin more plausible. Though studies supporting one or the other seldom explain why in detail, the M-shaped fin uses features near the base of the spines and on the vertebrae themselves to set them in sequence. The D-shape models likely use comparative anatomy as support. Neither approach yields definitive results, both have their merits—our statue sticks with the most defensible details of the 2014 model wherever possible. Interestingly enough, one study argues that the M-shape, similar to that of a sailfish, indicates a high swimming speed for Spinosaurus. Unfortunately, other details cast doubt on whether Spinosaurus could swim at all, and some details of sailfish sails used as the study describes do not apply to Spinosaurus, such as the sailfish’s ability to retract its sail and its cross section.
• Some scientists have suggested that Spinosaurus’ sail supported a hump rather than a thin sail. They cite the elongated spines on some mammal’s backbones as examples, and indeed, you may see such spines on the Mammuthus and Cervalces skeletons in the Stewart Museum. Coelodonta would also have them, but they naturally are not depicted in our fleshed-out woolly rhino sculpture. In this case, though, the devil is in the details: where each of the mammalian examples cited have spines which fan out laterally at their tops and get rough in that area, Spinosaurus lacks such details. The surface texture of Spinosaurus’ spines hints that the skin grew very close to the surface of the bone, and it likewise resembles textures found on Dimetrodon but not on mammals with bony hunchbacks. Function may well suggest other reasons why Spinosaurus would not have a hump: the shape of these spinal structures radically differs, suggesting radically different functions. In Mammuthus, Cervalces, Coelodonta, and as a general rule for mammals, these spines serve as anchors for the nuchal ligament, AKA the paddywhack (yes, that line in the folk song “This Old Man” isn’t just nonsense; it refers to using a nuchal ligament as a dog treat). The nuchal ligament attaches to the back of the head, runs down the length of the neck, and attaches to the spines of the first dorsals (vertebrae at the level of the shoulder blades). Humans have a comparatively underdeveloped nuchal ligament—it becomes especially prominent in mammals with long necks and a habit of traveling long distances. A quick look at the shoulder region of the dinosaur skeletons in the Stewart Museum shows that different rules apply to dinosaurs. The closest the Stewart’s dinosaurs get to this kind of spinal ligament arrangement would be Camptosaurus and Diplodocus. Camptosaurus’ elongated spines do not form a prominent fin but instead offer greater surface area to the tendons of its back for greater structural stability. Some of these tendons grew bony in larger individuals and some of its bigger relatives—on the left hip of our Camptosaurus skeleton and on the backbones above the hips you can observe tendons which did just that. The Prosaurolophus’ skeleton likewise displays these ossified tendons over its back and hips. The Diplodocus vertebrae found next to the stairs come from the shoulder region of the animal. Their spines did not grow long, but instead developed a series of fins and pockets, expanding the surface area for the attachment points of enormous ligaments which kept its neck supported by its shoulders, effecting the same job as the mammalian spines but using a different strategy. Spinosaurus spines bore no such structures, so the mammalian comparison probably does not apply. Dinosaurs just did things differently.
• Our sculpture was completed in 2017, so it was based on the initial work done on the neotype specimen as reported in 2014. In 2018, the same team that worked on the 2014 study announced that they had found more material: a mostly complete tail. Unlike this depiction of a skinny tail with speculative spiky scales, Spinosaurus’ tail had a fin running the entire length. Several hypotheses on the function of this tail currently compete with one another. Some say it may have been used for swimming. Tests of this hypothesis have so far been relatively simple and do not appear to account for the fact that the long spines on the top are angled so as to overlap 3-5 vertebrae for most of the length of the tail. This would stiffen long sections of the tail, meaning that if it were used for swimming, Spinosaurus swam in a way distinct from its modern relatives, crocodiles and birds. Others see similarities between this tail design and modern animals like the Basilisk lizard, which uses its tail and back fins for showing off. Time and further testing will hopefully resolve these hypotheses, but in any case, this skinny tail is now outdated. Since this sculpture portrays a specific model from a specific time, we currently have no plans to update it.
• Some marketing, including a little of our own, has portrayed Spinosaurus as growing bigger than Tyrannosaurus rex. In some ways, it certainly looks bigger, thanks to that tall sailback and growing longer than the longest known T. rex. This sculpture follows a conservative size estimate and measures 48 feet long; some estimates for Spinosaurus suggest 60 feet as a maximum! By comparison, the longest known T. rex measures 42 feet. When it comes to size comparisons, though, scientists prefer to use mass, with weight acting as a decent proxy for paleontology’s purposes. Unfortunately, mass estimates use a variety of methods and can often produce skewed results, especially when founded on scant material or unusual body plans. The well-studied T. rex estimates usually range around 7-8 tons and are fairly reliable thanks to years of study and lots of data, while the rarer, weirder, poorly studied Spinosaurus’ estimates vary wildly from 5 tons to 22 tons! Clearly the jury’s still out on that point!
• Behind the scenes: due to the controversy of its stance, whether it was bipedal or quadrupedal, an early rendering for this sculpture portrayed it as lying on its belly to reference the controversy without taking sides. This idea was scrapped in favor of the bipedal stance so as to show off the animal’s size.
• Behind the scenes: early plans for this sculpture considered placing it parallel to the river. Given the sculpture’s tall profile and the frequency of strong canyon winds, we decided to minimize its profile by facing it into the prevailing wind direction, making it look like it was climbing out of the river instead. Unfortunately, this sculpture’s problems with the wind did not end there. Flaws in its internal engineering cause it to shudder a little in the wind; the resulting kinetic energy gets focused at about the middle of the tail, causing it to crack. Efforts at redesigning this section are currently underway.