Summary:
{See also Amylocystis lapponica, Leptoporus mollis, Postia fragilis Table.} Features include narrow elongated shelves (may also grow flat) on pine wood that are soft when fresh, cream-colored at first but soon developing brownish to rusty brown stains, pores 3-4 per millimeter, and microscopic characters including allantoid spores, cystidioles, monomitic hyphal system, and pigmented thick-walled cap surface hyphae. The current name in the online Species Fungorum, accessed April 20, 2020, is Fuscopostia lateritia, but the current name in Mycobank, accessed the same day, is Postia lateritia. The description derived from Ryvarden(2).

Microscopic:
spores 4.5-6 x 1.2-1.6 microns, allantoid, colorless, inamyloid; basidia 4-spored, 13-22 x 3-5.5 microns, clavate to cylindric, with basal clamp connection; cystidia absent, some hyphoid cystidioles may occur in the hymenium, these 13-22 x 3-4.5 microns; hyphal system monomitic, contextual generative hyphae 2-5 microns wide, colorless, thin-walled to thick-walled, "with clamps although some scattered simple septa may occur"; gloeoplerous hyphae scattered throughout the fruitbody; hyphae of the cap surface slightly pigmented and usually thick-walled, (Ryvarden), spores 4.5-6.3 x 1.0-1.8 microns (Ginns(28))

Notes:
Postia lateritia is known in western North America from one collection in BC (Ginns(28)), and it occurs also in North Europe (Ryvarden(2)). "This polypore was recognized in 1992; before that, specimens of P. lateritia may have been mislabelled as either P. fragilis or P. leucospongia." (Ginns(28), with Latin names italicized)

Synonyms and Alternate Names:
Cerioporus leptocephalus (Jacq.) Zmitr.