Shellbark hickory is a large tree with short, stout limbs, narrow crown, and shaggy bark.
Leaves are alternate, compound, 12–24 inches long, with 7 leaflets; each leaflet 5–9 inches long, oval, broadest above the middle, edges finely toothed, dark green.
Bark is similar to shagbark hickory: gray, separating into long, thin shaggy plates hanging loosely, with ends curving away from the trunk.
Twigs are stout, dark brown to reddish-orange; pores narrow.
Flowers April–May; male and female flowers separate on the same tree; male catkins in threes, female flowers 2–5, at the ends of branches.
Fruits September–October; nuts solitary or in clusters of 2 or 3, egg-shaped to nearly globe-shaped, depressed at the tip, 1–3 inches long; husk to ½ inch thick; light to dark brown, smooth to downy, hard, splitting easily along the 4 ribs at maturity.
Similar species: Compared to shagbark hickory, shellbark has larger leaves, more leaflets (5–9 instead of 3–5), larger nuts, and orange twigs.