Leaves and stems:

The leafy frond, called a trophophore, is single near the top of the stem, oblong in outline, with 2 to 5(6) pairs of leaflets (pinnae), not typically folding in towards the stalk and not usually overlapping. The trophophore is 2.5 to 6 cm (1 to ~2½ inches) long, held erect, the stalk 1 to 17 mm (to 2/3 inch) long. The stem below the tropophore is 4 to 10 cm (to 4 inches) long.

The lowest pinnae pair are perpendicular to the stalk or slightly ascending and are often ragged along the top edge; the next higher pairs may be more ascending. Pinnae are mostly fan-shaped, the sides straight or concave, the curvature usually strongest at the base, and span an angle of 70 to 180 degrees with the lowest pair usually largest. The tip edge is scalloped, toothed or irregularly notched. Pinnae of robust plants tend to have multiple lobes mostly rounded at the tip.

Fruit:

At the top of the stem is the fertile frond, called a sporophore, 2.5 to 9.5 cm (to 3¾ inches) long, rising above the tropophore at the end of a stalk about as long as the tropophore at maturity. The sporophore typically has numerous short branches, each with a few to several round capsules of spores (sporangia) that mature starting in June and turn brown after spores are released in July. At maturity, the branched part of the sporophore is about as long as its stalk.

Notes:

Crenulate Moonwort was first described as a species in 1981 and has a scattered distribution in western North America. It is noted as the most hydrophilic Moonwort, which means it has a strong preference for the wet soils typical of swamps and wet meadows. To everyone's surprise, it was discovered in Minnesota in 2011 at the edge of a hardwood forest where it transitions to a wet meadow, and was confirmed by genetic testing. It is currently only known from 3 locations in the state. There are also a reports of it scattered across the southern half of Canada. While it is not currently officially listed as rare in the state, a status of Endangered seems likely the next time the list is updated.

Its form can vary depending on habitat. Under the cover of shade, the pinnae tend to be smaller and fewer, where in sunnier spots the pinnae tend to be larger, more numerous, and often deeply notched with 2 or more lobes. In either case, the tropophore is usually stalked, pinnae are fan-shaped, the lowest pinnae pair tends to be perpendicular to the stalk or nearly so, spans an angle of up to 180 degrees, and its tip edge is often ragged. The pinnae above it tend to be more ascending. Pinnae tips are scalloped, toothed or irregularly notched. At maturity, the sporophore stalk and the branched part are each about as long as the tropophore.

Most similar is B. neolunaria (New World Moonwort), which has a stalkless tropophore, pinnae of robust plants are often overlapping, and its sporophore stalk is usually longer than the tropophore. Also similar is B. minganense (Mingan Moonwort), which typically has more pinnae that are all ascending, and pinnae tips tend to be smooth, scalloped or shallowly notched. B. ascendens (Upswept Moonwort) has narrower pinnae (45-70 degrees) that are more strongly ascending, edges are rather toothy, lobes tend to be more squarish or wedge-shaped, and its sporophore stalk is about half as long as the tropophore.

The shape of the pinnae may be similar to other Botrychiums as well, but these can all be variable on individuals so it's helpful to examine multiple plants within a population (if you can find them). Having said that, Botrychium identification is difficult even for the experts so don't be discouraged if you struggle to get it down to species.