Anisoptera megistocarpa (Dipterocarpaceae) known locally as Mersawa merah, can be found on well-drained and undulating areas of lowland forests. Merah refers to the colour of its leaves which is reddish brown on the under-surface. It is a large tree and is widely distributed in Southern Thailand, Peninsular Malaysia, Singapore and Northern Sumatra.

The diagnostic character of this species resides in the large leaf. The leaf is oblong or obovate-oblong averaging about 15 cm in length and can sometimes be as long as 20 cm. It is smooth and leathery in texture with about 30 or more nerves which are slightly sunken on the upper surface, and coarsely hairy and dark reddish brown on the under-surface.

Anisoptera megistocarpa has a large bole which sometimes attains a girth of up to 4 m. The colour of the bark is usually dull grey-brown or yellowish grey. The outer bark is thick with irregular flakes. The flowers are creamy white and the petals are ovate-lanceolate. The fruit measuring up to 22 x 3.8 cm, has 2 wings and the nut is crowned by a short and thick apiculus.

The timber that is produced from A. megistocarpa can be used for light construction and interiors, such as flooring, window frames and doors. However, owing to the high silica content of the wood which makes it difficult to saw, it is not popular with saw millers.

According to the Malaysia Plant Red List (Chua et al., 2010), A. megistocarpa is categorized as Vulnerable (VU B2b(iii)+C(II)). This species is threatened by land conversion activities. Even though several populations occur in the network of Totally Protected Areas, and it is assigned to a lower threatened category, the populations still require regular monitoring to ensure that the trees are conserved for the next generation.