Opuntia megacantha Salm-Dyck (1834: 363)

Neotype (designated by Scheinvar et al. 2010: 278): — MEXICO. Hidalgo, Villa de Tezontepec, 25 February 2009, Martínez-González & Scheinvar 7632 (MEXU!).

Description:— Arborescent habit, 2.0– 2.2 m high (Fig. 3A). Defined trunk of 30 cm in diameter, grayish scaly bark (Fig. 3B). Glabrous epidermis (Fig. 6C). Elliptical to oval cladodes, 28–35 cm long × 18–28 cm wide and 2–3 cm thick, green in color, covered with a light layer of wax (Fig. 4A). Areolas arranged in 8–9 series, 2.4 cm spacing between series, 2.2 cm spacing between areolas, elliptical shape, 0.3 × 0.2 cm, short black trichomes (Fig. 4B). Very short brown glochids (0.1 cm). 1–7 flexible, radial and diffuse white spines, yellowish apex, conical rigid central spines, some twisted, erect, diffuse and radial, unequal of 0.4–2.6 cm long (Fig. 4C). Juvenile cladodes with prominent tubers, areolas with short brown to black trichomes, reddish bristel hairs, green erect subulate leaves, with reddish uncinate apex, white spines with reddish apex (Fig. 3C). Acute flower buds, green perianth segments with reddish acuminate apex, obovate to elliptical pericarpel, slightly elevated tubers, areolas with short light brown trichomes, brown glochids and yellow bristle areolas (Fig. 4D and 4E). Yellow flowers (Fig. 4F), 6.0–7.0 cm long, turbinate pericarp, ca. 3.2 × 2.6 cm, areolas arranged in 4–5 series, 0. 6 cm spacing between each other, with crass basal scale, oblanceolated outer segments of perianth, mucroned apex, smooth, yellow edges, with medium green striation, oblanceolated inner segments, emarginated apex, yellow, slightly toothed upper edges, stamens 1/3 of the length of the perianth, white filaments with yellowish tones, yellow anthers, white cuneiform style, ca. 1.9 cm long, usually ten green papillary lobes of the stigma, ca. 0.6 cm long, with medium white striation (Fig. 3D). Elliptical to obovate (Fig. 5B), red fruits, 5.1–7.0 cm long, striated and slightly sunken floral scar, large, circular areolas (Fig. 5C), arranged in 6–7 series, 1 cm spacing from each other and 1 cm between series, long black trichomes, absent spines, brown glochids, sweet and juicy red funicles (Fig. 5D). Kidney shaped seed with irregular lateral aril, lateral yellow-micropillar region, micropiles and funicles included (Fig. 5F).

Micromorphology:— Thornswith lignified epidermal cells 140.51 ± 3.1 × 36.32 ± 2.3 μm in the distal part (Fig. 6B), 94.97 ± 1.50 × 18.20 ± 2.40 μm, non-continuous epidermal cells with fissures between cells and smooth texture, in the middle part (Fig. 6B). Glabrous epidermis, irregular epidermal cells (Fig. 6C) and tetracytic stomas (Fig. 6D). Polyhedron-shaped pollen grain, pantoaperturate (Fig. 6E), 102.08 ± 1.90 μm in diameter, 8050.69 μm ² in area, 16.27 ± 1.80 μm distance between each distal opening (pores), with a diameter of 22.21 ± 1.50 μm, 20–22 pores with walls of 1.15 ± 2.00 μm width and wart (Fig. 6F).

Vernacular names:— Sangrita (e.g., Reyes-Aguëro et al. 2009).

Phenology:— Opuntia megacantha blooms from March–April, whereas fruiting time if June–July.

Habitat and distribution:— Opuntia megacantha is species endemic to Mexico, it is known in the states of Aguascalientes, Coahuila, Durango, Guanajuato, Hidalgo, Jalisco, Oaxaca, Querétaro, San Luis Potosí, Sonora, Tamaulipas, Tlaxcala and Zacatecas (see e.g., Guzmán et al. 2003, Scheinvar et al. 2010, Hernández et al. 2014) (Fig. 2). It grows in xerophytic scrub (Rzedowski 1978).