I think this is A. elongatus, which is a bit larger than A. abnormis, and with slightly different sculpture on the elytra and pronotum. Males of A. elongatus have conspicuous earwig-like pincers extending from the abdomen, but in the image above I can't tell whether the dark object at the end of the beetle is a pincer or simply a stone.
I've changed my mind on this one - it's probably A. miraculus, which has the costae (raised lengthwise ridges) of the elytra alternately higher and lower. Although the location is written as 'Cotter River', the map indicates Piccadilly Circus which is a known locality for A. miraculus, whereas A. elongatus is a lowland species found around Canberra.