A modern vision of Stegosaurus on display at the Utah Field House of Natural History in Vernal.
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Photo by Brian Switek.
A modern vision of Stegosaurus on display at the Utah Field House of Natural History in Vernal.

Out With the Old Stegosaurus

Dinosaurs have changed quite a bit since I was a kid. Tails have been lifted, spines adjusted, skulls switched around, wrists repositioned, and feathery body coverings added, just to start. But some dinosaurs have changed more than others.

The tottering, lizard-skinned Tyrannosaurus rex of my youth shuffled awkwardly after whatever was slow enough to catch, while the modern visions of the carnivore depict a fluffy tyrant with a spine held parallel to the ground and a respectable 10-15 mile per hour run. T. rex almost three decades after I first met the predator is a very different animal. But the great armor-plated dinosaur Stegosaurus hasn’t undergone the same degree of sweeping alterations. Not quite.

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An oldschool Stegosaurus as illustrated by Charles R. Knight, featuring parallel plate rows and too many spikes. Image from Wikipedia.

When I visited Yale’s Peabody Museum of Natural History in New Haven, Connecticut last week, I didn’t immediately realize the ways in which the oldschool stegosaur was still off. Aside from too many tail spikes – eight in total, instead of four – the skeletal details looked more or less right. But then I noticed that the dinosaur’s tail was forced downward as much as the articulations allowed; the herbivore’s plates were arranged improperly in double, parallel rows; and the arms of Stegosaurus were splayed out to the side in the classic reptilian pose. And even though these particulars might seem minor, together they made the dinosaur seem just as awkward and dim-witted as I had often been told it must have been.

Stegosaurus isn’t going to stand like this forever. The Yale museum’s staff have big plans for their Stegosaurus, as well as their other dinosaurs. (I got a peek at the new fossil hall floor plans during my visit, and the new exhibits will be stunning.) But, for now, the Peabody’s Stegosaurus stands as a vestige to the slow, stupid, drab dinosaurs of my youth – an idiotic reptile that slouched through the Jurassic rather than proudly showing off its dermal decorations as the creature does in modern restorations.

Contrary to what I learned as a kid, Stegosaurus did not have a butt brain, nor did the dinosaur rely on the sun to warm up. And despite the variety of Stegosaurus renditions out there, lovely skeletons and evidence gleaned from them have shown that the famous dinosaur had plates arranged in a single alternating row and a thagomizer bearing four spikes. Stegosaurus was still among the oddest of all dinosaurs, but the image of the hefty herbivore as a stooped, moronic pile of ectothermic armor has been extinct for years now.

The constant wrangling of facts and theory have created an updated image of a more respectable and active dinosaur. Stegosaurus was not a prime example of extinction caused by investing too much energy in armor, as some 20th century paleontologists and pacifists, respectively, liked to claim. But the changes Stegosaurus has undergone since the days of the “Dinosaur Renaissance” seem relatively minor compared to earlier transfigurations.

The Yale paleontologist Othniel Charles Marsh named Stegosaurus in 1877. At the time, the infamous Bone Wars scientist had relatively little of the dinosaur’s skeleton to investigate and researchers had not even an inkling that anything like Stegosaurus (as we now know the dinosaur) ever existed. So we can’t really blame Marsh when he arranged the few known bones and plates into the form of a huge, turtle-like creature with a shell made of interlocking bits of triangular armor. (This is why the name Stegosaurus translates to “roofed lizard.”)

As he did with other dinosaurs – such as what became Triceratops, first described as a huge bison – Marsh changed his hypotheses based on new evidence. Additional Stegosaurus material showed him that his turtle-like interpretation was wrong for the plates, but the dinosaur’s spikes remained a puzzle. Marsh speculated that the weapons might have jutted from the dinosaur’s wrists as lances to jab and parry. This, too, turned out to be wrong when a quarry sketch showed the conical weapons in close association with the dinosaur’s tail. Marsh tweaked his speculations again, and finally, by about 1887, the standard form of Stegosaurus trod into view.

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A modern vision of Stegosaurus, as restored by John Conway.

Stegosaurus will keep changing. How could it not? The dinosaur lived 150 million years ago, and we will never see a live one. Our understanding of what the dinosaur looked like and how the animal actually lived rely on the limits of what’s preserved in the rock and our ability to pull secrets from fossils, as well as whether or not we’re asking the right questions as we’re approaching the dinosaur’s remains. We can see Stegosaurus with greater clarity than ever before, yet many of the biological basics of the dinosaur – its physiology, how it ate, and what those funky plates were actually for, to name just a few – continue to confound and inspire. Decades down the line, should I be fortunate enough to still be alive, I may look back at this post, shake my head, and realize how little we yet knew about the late, great Stegosaurus.