Dipterocarpus oblongifolius is a tree species from the family Dipterocarpaceae that is native to the tropical rainforests of Malaysia (Ruziman et al., 2022). In Peninsular Malaysia, the species is commonly known as Keruing neram or Nerang, while in Sarawak it is called Ensurai (Wong, 2002; Ahmad Fitri et al., 2022). The term "keruing" is the standard Malaysian name used for the timber of Dipterocarpus species (Wong, 2002). Meanwhile, the name “Neram” is associated with swift flowing rivers in Malaya because the species is closely linked to riverbank habitats (Corner, 1940, Corner, 1978). The scientific name “oblongifolius” refers to the elongated or oblong shape of its leaves (Corner, 1940).
The species is distributed in Borneo, Malaya, Myanmar, and Thailand (POWO, 2026). In Peninsular Malaysia, D. oblongifolius is found especially on the eastern side of the Main Range (Henderson, 1935). The species has been recorded in several states, including Kedah, Kelantan, Terengganu, Pahang, and Perak and commonly grows in lowland forests along riverbanks beyond tidal areas at elevations up to 400 m, while in Sarawak it can occur in riparian forests up to 600 m altitude (Yong et al., 2021).
Dipterocarpus oblongifolius usually grows along the banks of fast-flowing rivers and often leans over the water (Ahmad Fitri et al., 2022). The species is highly adapted to riverbank environments and can survive strong river currents and floods due to its extensive root system, which firmly anchors the tree to steep banks (Henderson, 1935). The tree also supports many epiphytic plants, especially orchids and ferns, which commonly grow on its stem (Ahmad Fitri et al., 2022). Historical observations recorded that a single tree may support at least 87 species of epiphytes (Saw, 2010). The species relies on water currents to disperse its fruits (Saw, 2010).
This species is characterised by a twisted or flattened trunk that develops into large branches and often forms large buttresses along riverbanks (Corner, 1940). The leaves may turn scarlet before falling, while the flowers are fragrant and the fruits possess a velvety calyx with wavy ridges (Corner, 1940). Young plants have narrow, linear leaves that gradually develop into broader, elliptic leaves as the tree matures (Saw, 2010). Although the species produces timber, it is not widely used because the trees are often poorly shaped (Ahmad Fitri et al., 2022). Among the Dayak Ransa and Limbai communities, the fruit is traditionally used as bait for catching semah fish (Gunawan et al., 2021).
The conservation status of D. oblongifolius is classified as Least Concern (LC) in Malaysia, including Peninsular Malaysia (Chua et al., 2023; Yong et al., 2021). The species is also found within Totally Protected Areas in Peninsular Malaysia, Sabah, and Sarawak. However, forest degradation and encroachment remain threats to the species in some parts of Malaysia, although it is still considered widespread and common in many riverine forests (Chua et al., 2023).
