Deinacanthon Mez (in A. & C. de Candolle, Monogr. Phan. 9: 12, 1896). Type: Rhodostachys urbaniana Mez. — Bromelioideae — Lit: Castellanos (1954: ethnobotany). Distr: Paraguay, Bolivia, N Argentina. Etym: Gr. ‘deinos’, dreadful, terrible; and Gr. ‘akantha’, thorn, spine; for the spination.

Perennial terrestrial rosette plants with long horizontal rhizomes; Ros stemless, with 10–15 (rarely more) leaves; L to 30–40 × 1–1.5 cm, erect to spreading, sheath indistinct, narrowly ovate, lamina straight to arching, stiff, succulent, somewhat canaliculate, glabrous and often slightly shiny above, with scaly indumentum below, margin serrate, marginal Sp to 3 mm, ±5 mm distant, brown to black, pungent, antrorse and/or retrorse; Inf terminal, sessile, condensed, few-flowered, 3 cm ∅, surrounded by entire small innermost rosette leaves that grade into bracts, inner Bra membranous with thickened tip and hyaline margins, ovate, 18–27 × 7–10 mm; Fl roughly cup-shaped, dirty whitish to pale cream, ill-scented or unscented, with abundant nectar; Sep slightly asymmetrical, 15 mm, erect, subovate-elliptic, mucronate and spine-tipped; Pet 19 mm; Fil connate with the petals for ; Anth 6 mm; Ov obtusely trigonous, 11 × 5–6 mm, subclavate-cylindrical, tomentose, with numerous ovules; Sty columnar, massive, short; Sti spiral, 4 mm; Fr berries, dry at maturity, globose to ellipsoid, to 35 × 25 mm, yellowish-orange, basally with scaly tomentum, apically with the dry perianth remains; Se cuneate to semilunar, brownish to pale.

The monotypic genus differs from Bromelia (where its species was for long classified) by the simple sessile inflorescence and spinose-mucronate sepals. Deinacanthon belongs to a group of early-diverging lineages within Bromelioideae, and forms a weakly supported clade with Ochagavia + Fascicularia and Greigia (Schulte & al. 2005, Horres & al. 2007, Schulte & al. 2009, Givnish & al. 2011). Evans & al. (2015) found Deinacanthon imbedded in Ochagavia, which also includes Fascicularia in their tree (Greigia not sampled).

D. urbanianum (Mez) Mez (in A. & C. de Candolle, Monogr. Phan. 9: 13, 1896). Type: Argentina, Córdoba (Hieronymus s.n. [G?, B, CORD, GH, US]). — Distr: Gran Chaco regions of Paraguay, lowland Bolivia (Santa Cruz) and N Argentina (Chaco, Salta, Tucumán, La Rioja, Córdoba, San Juan, San Luis, Mendoza); sandy and clayey soils in chaco and monte vegetations, 500–850 m. I: Luther (2005); Subils (2009: 341). – Fig. 1.

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Deinacanthon urbanianum. (Copyright: U. Eggli)

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≡Rhodostachys urbaniana Mez (1891) ≡ Bromelia urbaniana (Mez) L. B. Smith (1967).

Description as for the genus.

The flowers are described as ill-scented by Castellanos (1954), but later authors have not repeated this observation, and cultivated plants produced unscented flowers (pers. obs.). D. urbanianum is one of several species from the Gran Chaco region known as “chaguar” and was used to produce fibre. Castellanos (1954) describes the method used by the Mataco (Wichí) ethnic group in N Argentina. Biurrun & al. (2007) report that the fruits are edible and were formerly eaten in La Rioja province.