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FNA | Family List | FNA Vol. 4 | Cactaceae

22. Sclerocactus Britton & Rose, Cact. 3: 212, fig. 224. 1922.

Eagle-claw cactus, fishhook cactus [Greek sclero, hard, cruel, in reference to the hooked spines, and Cactus, an old genus name]

Kenneth D. Heil & J. Mark Porter

Coloradoa Boissevain & C. Davidson; Ferocactus Britton & Rose sect. Sclerocactus (Britton & Rose) N. P. Taylor; Pediocactus Britton & Rose sect. Sclerocactus (Britton & Rose) Halda

Plants erect, usually unbranched, sometimes deep-seated in substrate in winter but never flat-topped. Roots diffuse. Stems unsegmented, pale to dark green or bluish green, ovoid, spheric, depressed-spheric, depressed hemispheric, cylindric, or elongate cylindric, 1-40(-45) × 1.8-15(-20) cm, occasionally glaucous; tubercles usually coalescent into ribs (rarely remaining as separate tubercles); ribs 10-17(-20), crests deeply notched above each areole, thus ribs tuberculate; tubercles ± prominent on ribs; areoles 8-20 mm apart, elliptic to pyriform, with fertile portion as short adaxial prolongation confluent with spine cluster or connected to spine cluster by very broad groove, woolly; areolar glands few or absent; cortex and pith highly mucilaginous. Spines 2-17(-29); radial spines 2-11(-18) per areole, usually white or gray, sometimes straw colored, brown, pink, purplish pink, or black, straight or curved; central spines (0-)1-6(-11) per areole, gray, white, yellow, straw colored, red, reddish brown, brown, pink to purplish pink or black, usually of 2-3 distinct types, 1 or more hooked (rarely none hooked), acicular or subulate, or both (ribbonlike and papery in S. papyracanthus), longest spines 7-15 mm. Flowers diurnal, borne at adaxial edge of areoles at or near stem apex or in short extension of spine-bearing areoles, campanulate or funnelform, 1-6.7 × 1-6(-7) cm; outer tepals with greenish lavender, reddish brown, yellowish brown, or purple midstripes, white, cream, gold, rose, pink, or purple margins, oblanceolate, 10-45 × 3-10 mm, margins entire or fimbriate; inner tepals erect to ascending white, cream, yellow, or pink to purplish, often with dark midstripes, lanceolate to oblanceolate, 15-50 × 4-12 mm, margins entire or fimbriate; ovary scaly, spineless; stigma lobes 5-12, pink, green, yellow, or creamy white, 1.5-3.5 mm. Fruits dehiscent along 2-4 irregular, short vertical slits above base, or through basal abscission pore, green, often turning tan, pink or red, cylindric to subspheric, 4.2-30 × 3.5-21(-25) mm, thin walled, fleshy, becoming dry at maturity, naked or with few broad, thin scales; pulp greenish to white, scant; floral remnant persistent. Seeds brown or black, 1.5-3 × 1.9-4.5 mm, glossy or shiny; testa papillate (rarely furrowed). x = 11.

Species 15 (15 in the flora): w United States.

There has been considerable controversy concerning generic circumscription of Sclerocactus. Some treatments include Ancistrocactus, Echinomastus, Glandulicactus, and Sclerocactus as a single genus; whereas others exclude those groups, in addition to Toumeya, from Sclerocactus. Molecular phylogenetic studies of chloroplast DNA sequences (J. M. Porter et al. 2000; R. Nyffeler 2002) support a close relationship among Ancistrocactus, Echinomastus, Toumeya, and Sclerocactus; only Toumeya is included with Sclerocactus here. Although morphologically cohesive, Echinomastus is inferred to be a paraphyletic group, with some species (i.e., E. johnsonii) more closely related to Sclerocactus than to other members of Echinomastus. Ancistrocactus is sister to Echinomastus and Sclerocactus, providing merit to a broader circumscription of Sclerocactus. Glandulicactus and Pediocactus are only distantly related to this group, bolstering their exclusion from Sclerocactus.

Toumeya Britton & Rose is an illegitimate name that pertains here.


Heil, K. D. and J. M. Porter. 1994. Sclerocactus (Cactaceae): A revision. Haseltonia 2: 20-46. Hochstätter, F. 1995. The genus Sclerocactus (Cactaceae)---Part 1. Cact. Succ. J. Gr. Brit. 13: 73-79. Hochstätter, F. 1996. The genus Sclerocactus (Cactaceae)---Part 2. Cact. Succ. J. Gr. Brit. 14: 76-84. Hochstätter, F. 1996b. The genus Sclerocactus (Cactaceae)---Part 3. Cact. Succ. J. Gr. Brit. 14: 183-188. Hochstätter, F. 1997. The genus Sclerocactus (Cactaceae)---Part 4. Cact. Succ. J. Gr. Brit. 15: 74-81.

1 Central spines (0-)1(-4) per areole, ribbonlike, flexible, twisting or curled, papery, with obscure adaxial midrib, lacking hook, if central spine absent, then radial spines strongly flattened   15 Sclerocactus papyracanthus
+ Central spines (0-)1-6(-11) per areole, terete to angled, or if all flattened and papery, then some hooked, if central spine absent, then radial spines not flattened   (2)
2 (1) Abaxial central spine nearly always absent , if present, then hooked, 7-15 mm, brown; flowers yellow or cream (rarely pink); nw New Mexico and sw Colorado   8 Sclerocactus mesae-verdae
+ Abaxial central spines nearly always present, usually hooked (sometimes straight), 10-100 mm, variable in color; flowers variable in color, but if from nw New Mexico, then deep pink to purple, never cream to golden; widespread   (3)
3 (2) Fruits dehiscent by 1-4 vertical slits forming before fruits dry   (4)
+ Fruits not vertically dehiscent, irregularly shattering when dry or dehiscent through basal abscission pore and easily removed when fruits still succulent   (7)
4 (3) Flowers yellowish, 2.5-3 cm; inner tepal margins crisped or minutely toothed; styles minutely but densely papillate; radial spines usually 6-8 per areole, to 15 mm; nc Arizona   12 Sclerocactus sileri
+ Flowers lavender, red-purple, pink, or yellow, 2-5 cm; inner tepal margins entire to minutely toothed; styles very minutely and sparsely papillate, appearing smooth; radial spines usually 8-11 per areole, to 35 mm; w Utah, Nevada   (5)
5 (4) Flowers cream with yellow, greenish, reddish purple, lavender, or brownish margins; inner tepal apices generally rounded, usually not mucronate; adaxial central spine usually to 25 mm, 0.7 mm wide at base   9 Sclerocactus pubispinus
+ Flowers usually violet to rose or pink (rarely cream); inner tepal apices usually mucronate; adaxial central spine to 30-50+ mm, to 16 mm wide at base   (6)
6 (5) Central spines pubescent only in very young, pre-reproductive plants; lateral central spines 10-30 mm, terete; adaxial central spines 1-3 per areole, 0.7-1.6 mm diam   10 Sclerocactus spinosior
+ Central spines pubescent in young and early reproductive plants; lateral central spines 10-40 mm, usually terete, sometimes flattened and ribbonlike; adaxial central spine usually 1 per areole, 1.5-2.5 mm diam   11 Sclerocactus blainei
7 (3) Hooked spines typically 5 or more per areole; California, Nevada   (8)
+ Hooked spines 0-4 per areole; Arizona, Colorado, New Mexico, Utah   (9)
8 (7) Central spines usually 9-12 per areole; radial spines 20-50 mm; flowers 5-10 cm; fruits 2.2-5 cm; California, Nevada   13 Sclerocactus polyancistrus
+ Central spines usually 6-8 per areole; radial spines 8-20 mm; flowers 3-4 cm; fruits 1.5-2 cm; Nevada   14 Sclerocactus nyensis
9 (7) Central spines straight, not hooked, if hooked, then shorter than 10 mm   (10)
+ Abaxial central spine hooked, generally longer than 10 mm   (12)
10 (9) Seed surface composed of convex cells; Colorado   3 Sclerocactus glaucus
+ Seed surface composed of flattened cells; Utah   (11)
11 (10) Abaxial central spines usually not hooked; perianth funnelform; outer and inner tepals brownish lavender, violet, or pink, 2.5-5 cm diam   5 Sclerocactus wetlandicus
+ Abaxial central spines often absent, or if present, then all curved or hooked; perianth campanulate; outer tepals greenish to purple, inner tepals purple, 1.1-3 cm diam   4 Sclerocactus brevispinus
12 (9) Flowers 2.2-3.5 × 1.5-3.5 cm; ovary minutely papillate, appearing smooth; adaxial central spine 1.5-2 mm wide, or if less than 1.5 mm wide, then radial spines 4-6 per areole; radial spines 4-12 per areole   (13)
+ Flowers 3-5.7 × 2-5.5 cm; ovary papillate, appearing granular; adaxial central spine 0.5-1.5 mm wide; radial spines 5-17 per areole   (14)
13 (12) Flowers yellow; radial spines 7-12; ne Arizona, se Utah   1 Sclerocactus whipplei
+ Flowers purple; radial spines 4-6; sw Colorado, nw New Mexico   7 Sclerocactus cloverae
14 (12) Flowers pale pink to white or cream; filaments magenta; central spines (3-)4 per areole, abaxial spine white to tan, 10-30 mm; fruits 0.9-1.5 cm   2 Sclerocactus wrightiae
+ Flowers purple, pink, or yellow (rarely white); filaments green to whitish, or if magenta, then flowers not pale pink or white; central spines 4-8 per areole, abaxial spine usually purple-black, 15-72 mm; fruits 1-3 cm   6 Sclerocactus parviflorus

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