Cupstones, also called anvil stones, pitted cobbles and nutting stones, among other names, are roughly discoidal or amorphous groundstone artifacts among the most common lithic remains of Native American culture, especially in the Midwestern United States, in Early Archaic contexts. The hemispherical indentation itself is an important element of paleoart, known as a "cupule". Cup and ring marks are also common in the Fertile Crescent and India, and later in the Mediterranean, Atlantic, and Alpine regions of Europe, sometimes associated with complex petroglyphs or megalithic monuments. Etymology One encyclopedia of archaeology treats "pitted stone", "cupstones", and "nutting stones" as synonyms and says that they "may have been formed by cracking nutshells, though this activity lacks adequate confirmation through ethnographic examples or published experimentation." Purpose These objects have received little study, perhaps because edged tools and weapons have more intrinsic interest to private collectors, but closer study of them might reveal something of domestic practices and toolmaking technology. There is no agreement upon their purpose or purposes, which may have included the processing of food, medicine or pigments, storage, arrow-production or fire-drilling. As such, they could represent a primitive form of mortar and pestle. The age of these man-made structures is difficult to ascertain, but generally they are believed to have been produced in the Bronze Age and Upper Paleolithic although some, for example in North America and Europe, were generated at a later date. Visually, they may resemble omarolluks, a naturally occurring feature of sedimentary rock occurring exclusively in the Belcher Islands, an archipelago accounting for 0.25% of Hudson Bay, whence they are thought to have been spread by glaciers. Distribution Similar objects can be found on all continents except Antarctica. They are associated with Celtic Europe, prehistoric Australia, Borneo and the Middle East. Some of the earliest cupules can be found at the Bhimbetka cave site in India, dating to 290,000-700,000 BCE, but in Europe they do not pre-date the most recent cold phase (the Würm or Weichselian glaciation). Some scholars insist the items are "false" artifacts, that is, their form results from natural processes rather than human activity. However, no one has yet described processes that might both produce such effects and also explain the distribution of the effects and the objects. Certainly air-bubbles in stone, broken open and eroded, could produce some of these phenomena. The objects are familiar in Illinois, Ohio, Indiana, Arkansas, Kentucky, Tennessee, Alabama