It seems likely that Phaeogyroporus portentosus is an indigenous species, for an immature specimen, indistinguishable from similarly aged specimens of  P. portentosus, has been collected in dense native forest near Rotorua by Mr. G. B. Rawlings. When the natural geographical distribution of the species is considered (Australia, Ceylon, Indonesia), its presence in the warmer parts of New Zealand is not unexpected.

The mycorrhizal status of P. portentosus is uncertain. Earlier descriptions contain little information about its habitat, but, on the basis of field observations, Fisch (1945) suggested that in Australia it formed mycorrhizal associations with Eucalyptus. The fungus has appeared in the Auckland Domain for a number of years and is restricted to a small area in a planted border of native trees and shrubs. The only plant with which it could form an association in this area is a single tree of Nothofagus truncata. The collection from Meadowbank was not associated with any known mycorrhizal plant.

New Zealand specimens agree closely with earlier descriptions of the species and with Australian specimens identified by Cleland (ADW), except that both Fetch (1907) and Boedijn (1951) described the pileus as smooth. P. portentosus readily fits within Singer's (1962) circumscription of Phaeogyroporus. although cystidia are absent. It seems likely that Phaeogyroporus is a later synonym of Phlebopus (Heim) Singer 1936. Singer (1962) regarded Phlebopus as a nomen dubium on the doubtful grounds that the type specimen of Boletus colossus Heim, the only species originally described in the genus, was no longer in existence. Heim (1965) recently pointed out that specimens of B. colossus are preserved in Paris (PC). The two genera appear to be closely related and, if on re-examination of B. colossus the presence of clamp connections is demonstrated, it will be difficult to maintain them as separate genera.

The genus Phaeogyroporus contains some of the largest Agaricales known: Cleland (1935) reported that specimens of P. portentosus reached 60 cm in diameter and weighed up to 7 lb 2 oz. P. portentosus is regarded as an edible species in Australia.

The species may be distinguished by the large, olive brown fruitbodies, short-elliptical spores, and the presence of clamp connections. It has not previously been recorded from New Zealand.