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
Animals (Scientific Procedures) Act 1986 be done through non-animal or in-vitro methods. The project must also pass an ethical review panel which aims to decide if the potential benefits outweigh any suffering for the animals involved. ASPA involves three levels of regulation — person, project, and place. The 'person' level is achieved by the granting of a "personal licence" (PIL, procedure personal licence) to a researcher wishing to carry out regulated procedures on a protected animal. Having undergone a defined sequence of training, a researcher can apply for a PIL permitting specified techniques to be carried out on named species of animals. The 'project' level