Dacrydium cornwalliana was first described by David J. de Laubenfels in 1988. He describes in as a tree growing 30 to 60 feet (10 - 30 m) tall, with an elongated dense, fastigiate crown . Juvenile leaves are up to one-half inch (12 mm) long, strongly curved forward, parallel to the branch and soon becoming incurved, with a sharply-pointed tip. Adult leaves are crowded and touching near their tips, spreading but then incurved towards the tip which is directed somewhat inward towards the branch, exceptionally pointed, 0.08 - 0.2 inch (2-5 mm) long, the longer examples on protected branches or younger trees, strongly keeled on the back and slightly concave on the ventral side but with a small ridge over the midvein. Fertile structures occur on the terminals, often on short lateral shoots but pollen cones may also be lateral. Pollen cones are around 0.5 inch long by 0.07 inch wide (12 x 1.8 mm). The seed-bearing structure as in D. nidulum, become fleshy and red when ripe.
Distribution. This species is native to western and central Papua New Guinea as well as Indonesia where it is
dominant in nearly pure stands in swamp forests and perhaps also mossy heath forests between elevations of 4,600 to 7,400 feet (1450 and 2300 m).