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A huge Ceratosaurus nasicornis on display at the Natural History Museum of Utah. Snapshot by Brian Switek.

Ceratosaurus Ink

Earlier this year, I got my first bit of science inkan Allosaurus fragilis contorted in the classic dinosaur death posean Allosaurus fragilis contorted in the classic dinosaur death posean Allosaurus fragilis contorted in the classic dinosaur death pose, drawn by Glendon Mellow. And as soon as I got that tattoo, I started thinking of a Jurassic complement to the art. The negative space around the twisted skeleton demanded another dinosaur. A Ceratosaurus nasicornis would be just the thing. Now that I’m all healed, I can proudly show off the opisthotonic ceratosaur.

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My new Ceratosaurus tatto. The arm at the top there belongs to an Allosaurus skeleton I had inked earlier this year. Photo by Tracey Switek.

This isn’t just any Ceratosaurus, though. It’s a specific dinosaur that was found alongside the bones that inspired my Allosaurus.

When Glendon illustrated my first tattoo, he drew the Allosaurus from a skeleton on display at the Royal Ontario Museum. Fortuitously, the mount has a connection to my home state of Utah. Despite being on exhibit hundreds of miles away, the ROM Allosaurus is based on material excavated at the Cleveland-Lloyd Dinosaur Quarry near Price, in the eastern part of the state. The fantastically-rich, 150 million year old bonebed has yielded remains from at least 46 Allosaurus individuals of different ages, along with the rarer remains of other carnivores. Mid-sized predators Marshosaurus and Stokesosaurus were first found here, and a collection of isolated bones gave away the presence of a huge Ceratosaurusa huge Ceratosaurus in the same deposit. That dinosaur was the inspiration for my new tattoo.

Ceratosaurus is a Jurassic classic, but remains poorly known. Even though 19th century paleontologist O.C. Marsh described and reconstructed the dinosaur based upon a mostly-complete, partly-articulated skeleton (later reassessed in more detail by Charles Gilmore), very few Ceratosaurus have been found since then. Allosaurus has a ubiquitous presence in the upper Morrison Formation sites, but Ceratosaurus was apparently a rarity among the ancient, fern-covered floodplains.

The scarcity of Ceratosaurus individuals has led to a bit of oversplitting. Marsh named the first species, C. nasicornis, in 1884. This was the sole species until 2000, when Utah paleontologist James Madsen, Jr. and posthumous collaborator Samuel Welles named two more species. Madsen and Welles named one, C. magnicornis, from a lovely specimen found in Colorado, and used the paltry Cleveland-Lloyd material to dub a second species – C. dentisulcatus.

Yet both of these dinosaurs are probably synonyms of Marsh’s original C. nasicornis. The slight differences seen in the Colorado animal are likely indicators of individual variation rather than definite marks of a distinct species, and the distinctive features seen in the Cleveland-Lloyd Ceratosaurus are probably marks of older age, underscored by the animal’s large size.

Although the animal is only partly known, you can get an idea of how large the Cleveland-Lloyd Ceratosaurus must have been by looking at Scott Hartman’s comparative reconstructions. Marsh’s dinosaur, on display at the National Museum of Natural History, was about 18 feet long. The Cleveland-Lloyd individual was bulkier and may have been about 22 feet long or more. It was certainly big enough to compete with the largest of the Morrison Formation apex predators – Allosaurus and the little-known Torvosaurus.

Given that no one has studied the histology and growth and Ceratosaurus in detail, though, it’s hard to say whether the Cleveland-Lloyd dinosaur truly represents a fully mature animal, or would have kept growing. As with many other Morrison Formation dinosaurs, there’s much we still don’t know about Ceratosaurus.

The Cleveland-Lloyd Ceratosaurus felt like a natural partner for my already-inked Allosaurus. I can’t help wondering about how such enormous predators partitioned the hyper-productive Late Jurassic landscape, and both skeletons symbolize one of the most important fossil assemblages ever found in my home state. Utah’s Late Jurassic brims with dinosaurs and fossil mysteries, and the two carnivores on my arm embody a time when dinosaurs truly ruled.

[I’m indebted to Glendon Mellow for drawing the Ceratosaurus skeleton, and Jon McAffee at Heart of Gold Tattoo for applying the ink. Now to decide which member of the Morrisson Formation cast is going to join my collection next.]