Hi treeguy,
I'm a relative newbie, but my understanding is that the full moon maples are a subgroup of japanese maples , some of which used to be called acer japonicum but have been reclassified as Acer shirasawanum. So you'll find them listed under either or both names - extremely confusing!

'Aureum' is a specific variety/cultivar within that group that has bright golden green leaves. I'm debating between getting one or a different variety called 'Autumn Moon' .
There may also be a specific variety called full moon - but I'm not sure and hope someone else here can clarify.
Thanks,
Lucy

Sorry, but these are two very separate species, although both included in the section and series Palmata, as are A. palmatum, circinatum, sieboldianum and several others, therefore will have some rather obvious similiarities of leaf shape/size, mature height, habit and cultural preferences. The difference between the two species superficially is leaf size - A. japonicum (fullmoon maple) generally has quite large and very orbicular or rounded leaves, sometimes very highly dissected. A shirasawanum tends to have similarly shaped but smaller leaves, less commonly dissected. At one time, 'Aureum' and other smaller leaved forms were considered cultivars of japonicum but were reclassified due to chemical and floral distinctions. Aureum and Autumn Moon are really the only cultivars of shirasawanum that are referred to with "moon" in the common name.

I find this confusing also. I have acer? Ogura Yama. It is listed as Sieboldianum, Synonyms, A. Japonicum,A. Shirasawanum. They seem similar and hard to tell apart with some plants. David

I stand corrected:). Thanks gardengal48! I appreciate having patient people here to earn from.

treeguy, this is an often asked question that stems from Acer shirasawanum 'Aureum' being formerly considered Acer japonicum. At that time it was given the common name "Golden Full Moon Maple", since then it has been correctly identified as Acer shirasawanum. The common name has stayed the same, which has led to confusion. What adds to the confusion is that it is still seen listed fairly regularly in garden periodicals as Acer japonicum 'Aureum' instead of Acer shirasasawanum'Aureum'. Basically I'm just reiterating what gardengal48 has said. She regularly impresses me with her knowledge and cool head. Later, Dan.

p.s. should read shirasawanum.I spelled it right the first time,but major typo the second time. Oops.