371.

Bornean Tree Rat

Pithecheirops otion

French: Pithécheir de Bornéo / German: Borneo-Affenful’ratte / Spanish: Rata arboricola de Borneo

Other common names: Bornean Pithecheirops, Emmon’s Tree Rat, Wooly Tree Rat

Taxonomy. Pithecheirops otion Emmons, 1993,

“Malaysia, State of Sabah [northern Borneo]; Danum Valley Field Centre, 4°58’'N, 117°48’E (approximately 75 km W Lahad Datu), elevation about 150 m.”

The monotypic genus Pithecheirops was described in 1993 by L. H. Emmons, who considered it close to Pithecheir in external morphology but distinguished by skull features. P. otion is known only from the type specimen, and there are no genetic data to support its phylogenetic position. In 2015, P. H. Fabre and colleagues placed it next to Pithecheir as a possible member of tribe Pithecheirini . Monotypic.

Distribution. Known only from type locality in N Borneo.

Descriptive notes. Head—body 113 mm, tail 117 mm, ear 15 mm, hindfoot 25 mm; weight 36 g. The holotype is a juvenile male in poor state of preservation. The dark gray-brown dorsal pelage is long and dense, and the underparts are whitish. The robust unicolored tail is naked and partially prehensile;it is slightly longer than headbody length. Feet are broad and have large plantar pads. Skull has a very short rostrum and a long and high braincase, but with small, uninflated tympanic bullae representing 16% of skull length (compared with 20-25% for Pithecheir representatives).

Habitat. Secondary forest (lowland dipterocarp forest selectively logged in 1989) at 150 m altitude.

Food and Feeding. No information.

Breeding. No information.

Activity patterns. Bornean Tree Rats are arboreal.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Data Deficient on The IUCN Red List because it is known from a single juvenile individual and population size is unknown. Further work is necessary to collect the species again and to gather ecological data.

Bibliography. Emmons (1993), Fabre et al. (2015), Musser & Carleton (2005).