What is a Thagomizer?

For many years the arrangement of spikes at the end of a stegosaur's tail was known as, well, the arrangement of spikes at the end of a stegosaur's tail. Then up popped Gary Larson in 1982 and did what no bright-minded anatomist had thought to do. He gave it a snappy, easy to pronounce name—the thagomizer.

In Larson's "The Far Side" comic strip, a group of cavemen in a faux-modern lecture hall are taught by their professor that the spikes were named "after the late Thag Simmons", implying that he had met his end after an unfortunate encounter with a stegosaur. The fate of cartoon Thag notwithstanding, dinosaurs and humans did not exist in the same era, and Larson later joked that there should be confessionals where cartoonists could go to seek forgiveness; "Father, I have sinned – I have drawn dinosaurs and hominids together in the same cartoon".

Nevertheless, "thagomizer" was picked up by Ken Carpenter, a palaeontologist at the Denver Museum of Nature and Science, who used the term when describing a fossil at the Society of Vertebrate Paleontology Annual Meeting in 1993. And it has been adopted by many scientists and institutions, including the Smithsonian, since then.