Rare fragments of jaw containing several teeth belonging the stem reptile Captorhinus aguti. The genus Captorhinus is of such special scientific interest because it is thought to include the ancestors of all terrestrial vertebrates excluding amphibians. The jaw fragments were found within the Permian - Leonardian sediments of the Arroyo Formation in Cherokee County, Oklahoma, USA. Initial fragments of the skull were described by world renowned palaeontologist, Edward Drinker Cope in 1882, Cope, who was famous for his bitter rivalry with fellow palaeontologist, Othniel Charles Marsh, with both men partaking in an era of fossil discoveries, slander, backstabbing, bribery and more becoming known as the infamous 'Bone Wars', named the fossils after the latin word, 'captor' meaning to 'catch'. These reptiles are thought to have lived on a diet of insects, smaller reptiles and snails; their sharp multiple-rowed-teeth support such an interpretation. The fragments measure between 1 and 2 cm and are supplied in a small plastic magnification box.