Felidae Oligocene, about 25 million years ago, with the appearance of "Proailurus" and "Pseudaelurus". The latter species complex was ancestral to two main lines of felids, the cats in the extant subfamilies and a third major group of extinct cats, which are assigned to the subfamily Machairodontinae. The machairodonts included the saber-toothed cats such as the "Smilodon". The "false sabre toothed cats", the Barbourofelidae and Nimravidae, are not true cats, but are closely related and together with Felidae and other cat-like carnivores (hyaenas, viverrids and mongooses) make up the feliform carnivores. Results of mitochondrial analysis indicates that all the Felidae descended
William Procter Prize for Scientific Achievement a principal event at the Sigma Xi Annual Meeting, where the recipient delivers the Procter Prize Address. The Prize is named for William Procter, an heir of one of the founders of the Procter and Gamble Company. He was active in Sigma Xi and its affiliated organization, the Research Society of America (RESA), and endowed the award that bears his name in 1950, the year before he died. William Procter Prize for Scientific Achievement The William Procter Prize for Scientific Achievement is an award given by Sigma Xi, a scientific-research honor society. The Procter Prize is presented annually to a