This native tree Mitrephora diversifolia is also known as the flying duck flower (No offence to whomever assigned that name but I can’t see any resemblance), and is one of the more glorious native members of the custard apple family here. The brilliant flowers can vary a bit in colour it seems and are quite large (I remember something ~5cm across). Like some species of the Custard Apple family, some of the floral parts of this species are fused at the tips to form somewhat of a basket. This feature is probably a nuptial chamber for beetles that pollinate the flower. The leaves are hairy, dark green above, and are ovate in shape. The twigs have numerous lighter coloured lenticels (pores).
Recent phytochemical research has shown that root extracts of the plant may have antimalarial activity (Mueller et al. 2009). The species is found in Cape York and also the Malesian region (which includes Southeast Asia) – I’d so love to see this in the wild.
Mueller D, Davis RA, Duffy S, Avery VM, Camp D, Quinn RJ. 2009. Antimalarial activity of azafluorenone alkaloids from the Australian tree Mitrephora diversifolia. Journal of Natural Products 72, 1538-40. doi: 10.1021/np900247f.