Austeria citrea

The fruitbody is a polypore and may grow either flat along the underside of its woody substrate or produce a short, shelf-like outgrowth from the wood. The fruitbodies are small, the flat forms spreading no more than a few square centimetres and the 'shelves' usually extend out no more than a centimetre or so.

The pore surface is white or off-white. When present the upper surface of the 'shelf' is bright sulphur yellow. In those fruitbodies that lack the 'shelf', the margins are yellow.  

The fruitbodies appear on wood and seem to prefer smaller twigs and leaf litter. It is fairly common but often grows within loose accumulations of twig/leaf litter and so is easily overlooked.  

For many years this fungus was known as Antrodiella citrea, the change to Austeria occurring in 2016.

Look-alikes

The combination of bright yellow& white should make this species unmistakeable. Flavodon flavus is another yellow flat or shelved polypore. However, it is a duller yellow (closer to mustard) and the pores also have that colour.