In the Middle Eocene (about 42 mya), the miacids started to branch into two distinct groups of the order Carnivora: the Feliforms and Caniforms. The miacid precursors to the extant Feliforms remained forest-dwelling, arboreal or semi-arboreal ambush hunters, while the Caniform precursors were more mobile, opportunistic hunters. While it is clear that the first Feliforms appeared at this time, there is no clear common ancestor of the Feliform families in the fossil records. As forest dwellers, the early Feliforms were subject to more rapid decomposition in the absence of sedimentary materials, resulting in large gaps in the fossil records.