The dura mater has two layers, or lamellae: The superficial layer (also called the periosteal layer), which serves as the skull's inner periosteum, called the endocranium; and a deep layer called the meningeal layer; the actual dura mater.
The term thagomizer was coined by Gary Larson in humor, in a 1982 Far Side comic strip, in which a group of cavemen in a faux-modern lecture hall are taught by their caveman professor that the spikes on a Stegosaur's tail are so named after the late Thag Simmons.
Larson's frequent use of animals and nature in the comic is popularly attributed to his background in biology. Reruns are still printed in many newspapers. The Far Side was ultimately carried by more than 1,900 daily newspapers, translated into 17 languages, and collected into calendars and 23 compilation books.