Cerion coccineum

The fruit body is flattish and often more-or-less disk-like, but sometimes irregular in outline. The surface is orange and is surrounded by an erect,  black rim that may be continuous (but uneven) or with say 2 or 3 breaks, thereby creating a few lobes.  

The fruit bodies appear on dead twigs, grow up to 2 millimetres or so in diameter and are likely to appear in groups. They develop within the wood and, when mature, break through the bark but remain largely immersed. 

The first description of this species (and also of the genus) was published in 1901, based on material collected in Tasmania. Since then specimens have been collected in South Australia, Victoria, NSW and the ACT. However, it has been been found rarely and it would appear that total herbarium collections are barely reach double figures!

Look-alikes

There is probably only one look-alike species - Therrya eucalypti. Its fruitbodies are flattish, the same size, orange, with a black rim and breaking through bark. It was first reported from Tasmania in 1997 and since then a few additional specimens have been collected in Victoria and NSW. On the Atlas of Living Australia you will find more reports of this species, based only on naked-eye observation, with no microscopic study of a specimen. Such reports are unreliable.    

Here (https://nzfungi2.landcareresearch.co.nz/Default.aspx?SpecimenID=102201591) you can find a photograph of a Therrya eucalypti collection that has been studied.