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
Fund for the Replacement of Animals in Medical Experiments Fund for the Replacement of Animals in Medical Experiments Fund for the Replacement of Animals in Medical Experiments (FRAME) is a charity based in Nottingham, UK. FRAME promotes consideration of the ethical and scientific issues involved in the use of laboratory animals for medical research, and the adoption of the Three Rs strategy of alternatives to animal testing. The Three Rs (Replacement, Reduction, Refinement) strategy was first suggested by zoologist William Russell and microbiologist Rex Burch, with Replacement being the ultimate goal. FRAME campaigns for the replacement of animal testing methods with alternatives that do not use animals. If there