Goniothalamus rotundisepalus is a species of plant in the family Annonaceae. It is native to Peninsular Malaysia and Thailand.[1] Murray Ross Henderson, the Scottish botanist who first formally described the species, named it after its sepals which are rounded like the arc of a circle (Latin: rotundatus in Latin).[2]
It is a bush reaching 1 to 2 meters in height. Its dark, young branches initially have fine red hairs, but become hairless when mature. Its papery, hairless, oblong to elliptical leaves are 10.5-23.5 by 3.5-8.5 centimeters with tips that taper to a point. Its leaves have 7-9 pairs of secondary veins that emanate from their midribs. Smaller veins create a fine network that gives the leaves a granular texture. Its solitary, pale green flowers are in supra-axillary positions. Its pedicels are 4-5 millimeters long and covered in sparse red hairs. Its sepals are rounded like the arc of a circle. The outer surface of the sepals are hairless or have fine sparse hairs and their inner surface is hairless. Its 6 leathery petals are arranged in two rows of 3. The lance-shaped outer petals are 2.5 by 1 centimeter and have sparse red hairs. The oval inner petals are 4-9 by 2.5-5.5 millimeters and have sparse red hairs on their outer surface and dense, coarse, brown hairs inside. Its flowers have 24-80 stamen. Its carpels have linear oblong ovaries covered in red hairs, thick style and two thick stigma surfaces. Its fruit are born on pedicels that are 4-8 millimeters long. The fruit are connect to the pedicels by 2-3 millimeter stipes.[3] [4]
The pollen of G. rotundisepalus is shed as permanent tetrads.[5]
It has been observed growing in lowland forests at elevations of 60 to 370 meters.[5]