The large Mindoro forest mouse is the third known rodent endemic to Mindoro, after the Mindoro black rat and the Mindoro climbing rat, and not including the Ilin Island cloudrunner, the occurrence of which has not been confirmed on the island. However, in a compilation work on the indigenous mammals of the Philippines, published in 1998, it was announced that there is a second "Apomys" on Mindoro. This species has yet to be described and has temporarily been given the name of ""Apomys" sp. E". It may be related to two other undescribed species from Sibuyan Island and Greater Negros-Panay, "Apomys" sp. A/C and "Apomys" sp. B. The local population of "A. musculus", the only other "Apomys" known on the island, may also represent a separate species. Several other species occur exclusively on Mindoro (in addition to the undescribed "Maxomys" species mentioned earlier), including Oliver's warty pig, the tamaraw and the megabat "Styloctenium mindorensis". The relatively large number of endemic species on Mindoro can be explained from the fact that, in all probability, Mindoro was never connected to any other landmass. This enabled the animals present on the island to develop in isolation from their relatives.