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.
About Gary Larson. American cartoonist Gary Larson has an estimated net worth of $50 million as of 2012. He is famous for being the creator of the internationally syndicated cartoon series The Far Side. For 15 years, the cartoon series was syndicated in over 900 newspapers worldwide. His collection of 23 cartoon books earned over 45 million sales copies. His world renowned cartoon series ended when he retired in 1995.