the current scientific name. The IUCN taxonomic note lists two subspecies, but the non-nominate one is poorly defined at present, so the species is treated as a whole. Tarsius syrichta carbonarius and Tarsius s. fraterculus were recognized by Hill (1955) as weakly defined subspecies. Niemitz (1984) found the differences to be insignificant based upon comparisons with museum specimens. Musser and Dagosto (1987) felt that the available museum specimens were insufficient to resolve the issue, but mentioned that Heaney felt that a single male tarsier from Dinagat might be distinct. Groves (2001) did not recognize any subspecies of C. syrichta, but Groves and Shekelle (2010) recognized the subspecies C. s. fraterculus, C. s. syrichta, and C. s. carbonarius when splitting the species of Tarsius into Carlito. Anatomy and morphology The Philippine tarsier measures in height, making it one of the smallest primates. The small size makes it difficult to spot. The mass for males is between , usually lighter for females, somewhat heavier than other tarsiers such as the pygmy tarsier. The average adult is about the size of an adult human fist. The female tarsier has multiple sets of breasts, but the only functional set is at the pectoralis. The other breasts are used as anchor points for the newborn tarsiers. The gestation period lasts 180 days, or 6 months, after which only one tarsier is born. The newborn tarsier is born with much fur and eyes open. Its body and head length is about 70 mm, and its tail is around 115 mm long. Like all tarsiers, the Philippine tarsier's eyes are fixed in its skull; they cannot move in their sockets. Instead, a special adaptation in the neck allows its round head to be rotated 180°. Their eyes are disproportionately large, having the largest eye-to-body weight ratio of all mammals. These huge eyes provide this nocturnal animal with excellent night vision. In bright light, the tarsier's eyes can constrict until the pupil appears to be only a thin spot. In low light or darkness, the pupil can dilate and fill up almost the entire eye. The large membranous ears are mobile, appearing to be almost constantly moving, allowing the tarsier to hear any movement. The Philippine tarsier has thin, rough fur which is colored gray to dark brown. The narrow tail, usually used for balance, is bald except for a tuft of hair at the end, and is