Creeping Buttercup

(Ranunculus repens) 4/21/12 Bombay Hook NWR Observation tower trail www6.
How to tell buttercups apart:
http://www.invasive.org/browse/subthumb.cfm?sub=6291&Start=1&display=60&sort=2
http://www.oardc.ohio-state.edu/weedguide/singlerecord.asp?id=310
"Similar Species: Creeping buttercup may be confused with other buttercup species. Tall buttercup (Ranunculus acris) can be distinguished from creeping buttercup by its upright growth habit. In addition, the leaves of tall buttercup are deeply lobed and toothed, but are not divided into 3 distinct segments like the leaves of creeping buttercup. Bulbous buttercup (Ranunculus bulbosus), a perennial, has 3-parted leaves like creeping buttercup, but has an erect growth habit. In addition, the stem of bulbous buttercup is swollen at the soil surface to form a bulb-like base and the sepals below the flowers droop towards the stem. Smallflower buttercup (Ranunculus abortivus) is an annual or biennial, and can be distinguished from creeping buttercup by its erect growth habit, much smaller flowers, smooth leaves and stems, drooping sepals, and very shallowly lobed basal leaves."