Thank you for your suggestion, Cariol. There was very little information to be found about Hymenocarpus circinnatus, The Plant List doesn't even recognize the genus, and some of the few references mentioin that Anthyllus circinnatus is a synonym, which this is definitely not. The photos of Hymenocarpus circinnatus I found on the internet do not look quite like those I saw, the flowers of the latter are much bigger and the colour is either very orange, almost coppert-like, or pale yellow, and the plants seem to be more compact. I guess I have to come back in summer and look at the seeds to get any closer.