A rare but large local Agaricus species we have found under Pinus radiata is this pinkish to greyish gold capped Agaricus from section arvensis that is closest on BLASTn to Agaricus megalocarpus from China. Largest cap was 17.5cms.
We called it Agaricus shaggylegs because its very thick fluffy scaling on the stipe/stem below the large ring. When damaged this mushroom smells potently of almonds and stains gold sometimes but not always.
Most of the times we have found this species we have assumed it was augustus and its pretty close (2% away or so on BLASTn).