Sanicula mariversa is a perennial herb that grows stout and erect, ranging from 40 to 70 cm tall, emerging from a stout caudex. It features caulescent, solitary stems that branch from above the base. The leaves are simple, with numerous alternate basal leaves and progressively reduced cauline leaves up the stem. Basal leaves are cordate-ovate to reniform, measuring 13-23 cm wide, and are palmately 3-lobed or 5-lobed, sometimes somewhat peltate. These segments are cuneate to obovate, deeply cleft to the middle or beyond, and variously lobed. Cauline leaves are more deeply lobed, and the blades are coriaceous. Margins of the basal leaves are spinulose–serrate, with cauline leaves more deeply lobed. Petioles of basal leaves are 1–3 dm long and abruptly short–sheathing; cauline leaves are subsessile. The flowers appear in +/- umbellately arranged terminal clusters of 2–5 pedunculate, capitate umbels and solitary to clustered umbels in the upper leaf axils, each hosting 10–20 flowers. Peduncles range from 0.5–2.5 cm long. The involucre consists of 8–12 oblong-lanceolate bracts, 1–3 mm long. There are typically 1–4 perfect, subsessile flowers and 7–14 staminate flowers with 3–5 mm long pedicels. Calyx teeth are ovate and about 1 mm long. The corolla comprises five yellow petals. It has five stamens and an inferior, 2-celled ovary with one ovule per cell. The styles are usually swollen at the base into a stylopodium and recurved twice as long as the calyx teeth. The fruit is ovoid, 4–6 mm long and 3–4 mm wide. The mericarps are slightly compressed dorsally in transection, covered with long, stout, uncinate, bulbous prickles, and the vittae are obscure. Seeds are 1 per mericarp; the embryo is small with a cartilaginous endosperm. It is found on xeric, well-drained slopes among Dodonaea, Schinus, shrubby Metrosideros, and grasses at approximately 750 meters.