Cotylelobium is a small genus belonging to the family Dipterocarpaceae. It has five species and is related to the genus Vatica. Of the five, only two species occur in Peninsular Malaysia, i.e. Cotylelobium melanoxylon and C. lanceolatum. Resak is the vernacular name for Cotylelobium melanoxylon in the peninsula while in East Malaysia, it is known as resak batu.

Cotylelobium melanoxylon is recorded from Tenggaroh Forest Reserve (FR), Jemaluang FR and Gunung Arong FR in north-eastern Johor. This species wide spread in Sabah and Sarawak, with several populations occuring in the network of Totally Protected Areas. It inhabits lowland areas up to hill dipterocarp forests at altitudes below 400 m and in kerangas (heath) on podsols. Populations of C. melanoxylon are usually located not far from the coast.

This species is a small tree with a girth 1-3 m. It has a smooth bole and is brightly coloured like that of a Vatica when young. The outer bark is pockmarked when young and irregularly scaly when old. The inner bark is about 8 mm thick and is tinged purple-pink. The leaf is glabrous with ovate or elliptic-ovate shaped and has about 12 pairs of main veins.

According to Malaysia Plant Red List (Chua et al., 2010), C. melanoxylon is categorized as Endangered (EN B2ab(iii)). Even though C. melanoxylon is not important to the timber trade, this species is threatened by land conversion and loss of habitats. In this respect, Forest Research Institute Malaysia (FRIM) in collaboration with Forestry Department of Peninsular Malaysia (JPSM) has undertaken in situ actions to conserve the populations in its natural habitats. One site in Gunung Arong FR is now a High Conservation Value Forest (HCVF). Hopefully with this measure, populations of C. melanoxylon will continue to survive.