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
World Day for Laboratory Animals groups opposed to the use of animals in research. In April 2010 protesters marched through central London calling for an end to the use of animals in research. A similar march took place in Birmingham in 2012. and Nottingham in 2014. World Day and World Week For Animals In Laboratories have also attracted attention from scientific groups defending the use of animals in research. On 22 April 2009 members of UCLA Pro-Test held a rally in support of biomedical research on animals, and to condemn the violence and harassment directed at faculty member Prof. David Jentsch by animal activists. NAVS