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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.
SELECTED REFERENCES 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.
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| 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 |
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15 Sclerocactus papyracanthus |
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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 |
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(2) |
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| 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 |
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8 Sclerocactus mesae-verdae |
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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 |
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(3) |
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| 3 (2) |
Fruits dehiscent by 1-4 vertical slits forming before fruits dry |
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(4) |
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Fruits not vertically dehiscent, irregularly shattering when dry or dehiscent through basal abscission pore and easily removed when fruits still succulent |
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(7) |
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| 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 |
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12 Sclerocactus sileri |
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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 |
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(5) |
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| 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 |
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9 Sclerocactus pubispinus |
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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 |
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(6) |
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| 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 |
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10 Sclerocactus spinosior |
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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 |
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11 Sclerocactus blainei |
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| 7 (3) |
Hooked spines typically 5 or more per areole; California, Nevada |
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(8) |
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Hooked spines 0-4 per areole; Arizona, Colorado, New Mexico, Utah |
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(9) |
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| 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 |
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13 Sclerocactus polyancistrus |
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Central spines usually 6-8 per areole; radial spines 8-20 mm; flowers 3-4 cm; fruits 1.5-2 cm; Nevada |
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14 Sclerocactus nyensis |
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| 9 (7) |
Central spines straight, not hooked, if hooked, then shorter than 10 mm |
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(10) |
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Abaxial central spine hooked, generally longer than 10 mm |
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(12) |
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| 10 (9) |
Seed surface composed of convex cells; Colorado |
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3 Sclerocactus glaucus |
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Seed surface composed of flattened cells; Utah |
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(11) |
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| 11 (10) |
Abaxial central spines usually not hooked; perianth funnelform; outer and inner tepals brownish lavender, violet, or pink, 2.5-5 cm diam |
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5 Sclerocactus wetlandicus |
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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 |
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4 Sclerocactus brevispinus |
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| 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 |
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(13) |
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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 |
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(14) |
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| 13 (12) |
Flowers yellow; radial spines 7-12; ne Arizona, se Utah |
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1 Sclerocactus whipplei |
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Flowers purple; radial spines 4-6; sw Colorado, nw New Mexico |
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7 Sclerocactus cloverae |
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| 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 |
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2 Sclerocactus wrightiae |
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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 |
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6 Sclerocactus parviflorus |
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List of lower taxa
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