I found this unusual seedling under my Scolopendrifolium, which did seed heavily last year (and a bit the year before). It has long, wavy, dissected leaves, which didn't start looking at all palmatum-like until the most recent leaf set. I got excited, thinking it was a seedling to watch, but when I flipped over the leaves to take photos they looked very grey. Is it possible it's a silver maple? There's a very large one in the neighborhood, but it's not a super-dissected silver maple cultivar. What do you think? Japanese maple or silver maple? The bark/trunk is pale green with short striated white marks. All the other details you can see in the photos.