Dinosaur’s mistaken identity: Torosaurus is a triceratops

New research suggests that two great horned dinosaurs, triceratops and torosaurus, are actually the same dinosaur at different stages of growth. Torosaurus, thought to be the largest horned dinosaur to ever walk the Earth, is actually an older triceratops. The discovery ends over 100 years of belief that the two were separate species.

Triceratops is a bit of a celebrity dinosaur, gracing the pages of hundreds of dinosaur coloring books, pajamas, bath toys, real scientific scholarship, and so on. It was discovered in the dinosaur rush of 1890s, and featured three large, exotic horns protruding from its skull.

Not long after triceratops came into the public eye, torosaursus was unearthed. It had one of the largest skulls of any known animal in history, with a skull that measured almost 9 feet in length. It was heavily horned like triceratops, but the shape of its skull was dramatically different. The triceratops had a curved, solid frill – that’s the name for that bony plate that extends above the dinosaur’s horns and covers its neck – whereas the torosaurus had a flatter, expanded frill with two holes in it.

The research team – Montana State University doctoral candidate John Scannella and one of the world’s most famous paleontologists, Jack Horner – are interested in how dinosaurs grow and mature. Palenontologists had always wondered why they never found any young torosaurus specimens. Scannella and Horner say that’s because they’ve been wrongly considering triceratops to be an adult dino. When they looked at the bone structure of the Triceratops, they discovered that it lacked the bone density that would have been expected in a full grown, adult dinosaur. But torosaurus had that mature bone.

So how could a dinosaur grow into such a different-looking skull? It’s because dinosaur skulls are made of metaplastic bone, a type of bone that can morph over time to form new shapes. That’s how torosaurus ended up with holes in its head, and got mistaken for a cousin, rather than a parent, of triceratops. But don’t worry about the beloved triceratops going away – because it was discovered first, the species will retain the name.

July 22, 2010

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