Buttercup confusion

It was a simple chance encounter. TPP was walking along a county park trail, and suddenly this cute little buttercup florally beckons, as it was intended.  A nearly 1" diam, bright yellow flower does get noticed when on a smallish plant, and while certainly a member of the buttercup genus, Ranunculus, what species was it?  This identification turns out to not be an easy task because a number of technical characters are involved to sort out the considerable number of both native and introduced species.  Fortunately, having an herbarium is a great asset and once things get narrowed down to a couple of species, you simply compare your plant to ones previously collected. In this case a couple of misIDed specimens were found too, showing that the confusion is nothing new.  To add to the problem the image is a bit over exposed so the pistils are hard to see.  Fortunately a hard-working master naturalist retrieved a specimen, and it was considerably easier, not easy, but easier, to ID when in hand (this early there were no mature fruitlets to examine (achenelets)).  So this appears to be R. fascicularis, which turns out to be similar to R. hispidus, which has a couple of varieties.