Thanks Rainer - Safarigirl Achenes are the developing fruit or seed conglomerate that develops in the centre of buttercup flowers. The individual seed cases or "fruit segments" are distinctive. If you are back this way could you please photo the fruits.
Safarigirl and Michael, I’d suspect you may actually need to look at the achenes under a microscope or at least a hand lens. I might be wrong ... check the Flora of NSW or PlantNet