Swamp Buttercup

Swamp Buttercup's shiny yellow flowers look a lot like Marsh Marigold flowers and the plants both grow in wet areas.  Marsh Marigolds bloom earlier-- they are mostly in seed now, while the Swamp Buttercups in Kalamazoo seem to be at peak flower.  Swamp Buttercups often grow in sunnier spots than the Marsh Marigolds.  The quickest way to distinguish these plants is to look at their leaves: Marsh Marigolds have round leaves while Swamp Buttercup leaves are pointy and divided into three lobes with jagged edges.

Swamp Buttercups (Ranunculus hispidus) are widely distributed through the central United States and Canada.  Until recently, Swamp Buttercups were considered to be a distinct species, Ranunculus septentrionalis, but they have been reclassified as a variety of Hispid Buttercup.

Apparently buttercups contain a harsh chemical, glycoside, that can cause skin irritation and blisters if you are exposed to the sap and poison livestock.  I've never considered picking or eating them, so no problems.