Epiphyte; stems thick, short, 3-6 cm diam.; leaf scars mostly hidden, ca. 2 cm wide; roots numerous, descending, ca. 6 mm diam., green with crusty tan epidermis; cataphylls coriaceous, 12-21 cm long, caudate-acuminate at apex, the apiculum ca. 5 mm long, drying tan (B & K Yellow-red 8/5), splitting al base, the apex remaining ± intact.

LEAVES held stiffly erect-spreading; petioles 10-55 cm long, 6-10 mm wide, ± quadrangular, 5-ribbed with 3 ribs on the abaxial side, sometimes with 2 additional ribs on the lower corners; geniculum 1.5-3 cm long, ribbed as the petiole; blades strap-shaped, gradually acuminate at apex, obtuse to slightly rounded at base, 45-85 cm long, 4-16 cm wide, broadest at middle, the margin flat to slightly undulate; upper surface semiglossy, lower surface matte to semiglossy; midrib convexly raised above, diminished at apex, sharply and obtusely raised below; primary lateral veins numerous on each side, departing midrib at 50°-60° angle, sunken above, sharply raised below, arcuate-ascending, prominently loop-connecting; interprimary veins numerous, slightly sunken above, prominulous below; secondary veins flat above, flat or slightly raised and darker below; collective vein arising from near base, about as prominent as the primary lateral veins, sunken above, prominently raised below, 2-7 mm from margin.

INFLORESCENCE erect or spreading at anthesis, ca. two thirds as long as leaves; peduncle 30-60 cm long, 6-10 mm diam., terete with a single dorsal rib, sometimes tinged purplish; spathe medium thick, green or green tinged with purple (B & K Yellow-green 7/10), oblong-lanceolate, 10-17 cm long, 2.5-4.3 cm wide, broadest at point of attachment, gradually and narrowly long-acuminate at apex, rarely short-acuminate, rounded at base, inserted at 50° angle on peduncle, often becoming coiled; stipe ca. 13 mm long in front, 1 mm long in back, 8 mm wide, tinged purple; spadix violet-purple (B & K Blue-purple 2/10), 10-20 cm long, 7-13 mm diam. at base, 5-6 mm diam. at apex; flowers 4-lobed, 2-2.5 mm in both directions, the sides jaggedly sigmoid, 7-9 flowers visible in principal spiral, 7-10 flowers visible in alternate spiral; tepals matte, the lateral tepals ca. 1.5 mm wide, the inner margin straight; the pistil emergent, orange-yellow; the stigma ca. 0.7 mm long, 0.2-0.3 mm wide, with conspicuous stigma droplets for several days before stamens emerge; stamens emerging ± rapidly from the base, the lower fourth with stamens emergent while apical flowers still are producing droplets on the stigmas; anthers pale orange, held just above tepals in a tight cluster, ca. 0.5 mm long, 1 mm wide; the thecae ellipsoid, scarcely divaricate; pollen white.

INFRUCTESCENCE pendent; spathe often missing; spadix usually 22-30 cm long, ca. 2 cm wide; berries orange, obovoid, flat to rounded at apex, 10-12 mm long; meso-carp orange, mealy, sweet tasting but pungent; seeds 2, + oblong with rounded corners, ca. 5 mm long, 4 mm wide, 2 mm thick. Figs. 176, 177,and 178.

Anthurium seibertii is known from higher altitudes in Chiriquí Province (1,300-2,000 m) and from one collection at 1,040 m in San José Province of Costa Rica (Skutch 2626, MO, US). The species is a member of the section Pachyneurium and is very similar to A. protensum. They share similar strap-shaped leaves, pale violet-purple spadices and orange berries. Anthurium protensum diners in having a nearly terete petiole while A. seibertii has petioles that are prominently ribbed abaxially and rectangular. Anthurium protensum also has leaves that are usually pendent and are generally smaller than those of A seibertii.

Map of Mesoamerican specimens with coordinates

Costa Rica Alajuela: 1375 m,, 16 Jan 1939, Smith 1498 (NY).
Costa Rica Lim—n: Valle de Silencio, 6000-6500 ft,, 9 Aug 1979, António 1675 (MO).
Costa Rica Puntarenas: 1700 m, 9.17N 83.13W, 24 September 1989, Abelardo Chacón 408 (MO).
Costa Rica Puntarenas: 1700 m, 9.17N 83.13W, 24 September 1989, Abelardo Chacón 409 (CR, MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 1500-1600 m, 09.02N 82.59W, 6 Sep 1984, Davidse et al. 28395 (MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 2000-2500 m, 09.03-6N 82.58-59W, 7 Sep 1984, Davidse et al. 28565 (CR, MO).
Costa Rica Puntarenas: Río Baru, 201 m,, 19 Aug 1983, Gomez et al. 21523 (MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 1800-2200 m, 09.49-57N 82.46-49W, 11 March 1984, Davidse et al. 25535 (MO).
Costa Rica Puntarenas: Canton de Coto Brus, 1200 m, 08.49N 82.58W, 6-7 March 1984, Croat 57259 (MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 1800-1850 m, 09.7N 83.4W, 20 March 1984, Davidse et al. 25613 (CR, K, MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 1800-1850 m, 09.7N 83.4W, 20 March 1984, Davidse et al. 25602 (K, MO, RSA).
Costa Rica Puntarenas: Río Cotoncito,, , Chacon et al. 1768 (DUKE, MO, RSA).
Costa Rica Puntarenas: Cordillera de Talamanca, 1800-1900 m, 08.59N 82.46W, 3 Sep 1983, G. Davidse 24528 (MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 1800-1900 m, 08.59N 82.46W, 3 Sep 1983, G. Davidse 24534 (MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 2000-2300 m, 09.00N 82.49W, 20 Aug 1983, Davidse et al. 23789 (MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 2300 m, 09.7-10N 83.4-00W, 28 March 1984, Davidse & Herrera 26179 (CR, MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 2300 m, 09.7-10N 83.4-00W, 28 March 1984, Davidse & Herrera 26183 (CR, MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 1800-1850 m, 09.7-10N 83.4-00W, 20 March 1984, Davidse et al. 25636 (B, MO).
Costa Rica Puntarenas: Río Baru, 2010 m,, 19 Aug 1983, Gomez et al. 21800 (CR, MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 2000-2300 m, 09.00N 82.49W, 20 Aug 1983, Davidse et al. 23791 (MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 2000-2300 m, 09.00N 82.49W, 20 Aug 1983, Davidse et al. 23790 (MO).
Costa Rica Puntarenas: Cordillera de Talamanca, 2000-2300 m, 09.00N 82.49W, 20 Aug 1983, Davidse et al. 23831 (MO).
Costa Rica Puntarenas: Monteverde Reserve, 11.20N 84.40W, 2 Sep 1981, Hepper 110 (BM).
Costa Rica Puntarenas: R.I. Ujarrás; Cordillera de Talamanca, 2200-2600 m, 09.21.10N 83.16.38W, 6 October 1989, Marlon Valerio 196 (CR).
Costa Rica San José: 1900 m,, 5 Sept. 1975, Utley & Utley 3059 (MO).
Costa Rica San José: 1040 m,, Feb. 1936, Skutch 2626 (F, MO).
Costa Rica San José: 1715 m, 09.28.34N 083.40W, 9 July 1992, Kress, W. et al. 92-3470 (INB).
Panama Chiriquí: Quebrada Velo, 5000 ft.,, 24 July 1947, Allen 4682 (G).
Panama Chiriquí: Boquete Region, 5500 ft,, 12 May 1971, Proctor 31816 (LL).
Panama Chiriquí: 08.50N 82.44W, 28 February 1985, Henk van der Werff & J. Herrera 7303 (MO, RSA).
Panama Chiriquí: Dtto. Bugaba, 1300 m, 08.50N 82.44W, 26 February 1985, Henk van der Werff & J. Herrera 7126 (B, MO).
Panama Chiriquí: Cerro Punta Region, 1800-2200 m, 8.53N 82.37W, 13 July 1983, C. Hamilton & K. Krager 3894 (B, K, MO).
Panama Chiriquí: Cerro Punta Region, 200 m,, 23 June 1970, Luteyn 902 (MO).
Panama Chiriquí:, 30 May 1979, Thomas B. Croat 10555 (MO).
Panama Chiriquí: Río Chiriquí Viejo, 1500-2000 m,, 16 Jan. 1939, Allen 1506 (MO).
Panama Chiriquí: Boquete Region, 1500 m,, 18 July 1940, Woodson & Schery 599 (MO).
Panama Chiriquí: Cerro Horqueta, 1500-1830 m,, 20 July 1968, Dwyer 8749 (MO, DUKE).
Panama Chiriquí: Cerro Punta Region, 2000-2170 m,, 7 May 1978, Hammel 2994 (MO).
Panama Chiriquí: Cerro Punta Region,, 24 Apr. 1969, Lazor 2727 (MO).
Panama Chiriquí: Cerro Punta Region, 2470 m,, 9 Apr 1979, D'Arcy et al. 13196 (MO).
Panama Chiriquí: 3000 m,, 8 Apr. 1979, Hammel et al. 6916 (MO).
Panama Chiriquí: Cerro Horqueta, 1870-2470 m,, 19 march 1979, Averett et al. 1084 (MO).
Panama Chiriquí: Río Caldera, 2130 m,, 20 March 1979, D'Arcy et al. 12761 (MO).
Panama Chiriquí: Cerro Punta, 2000-2330 m,, 22 Oct. 1977, Folsom 6035 (MO).
Panama Chiriquí: Boquete Region, 1670 m,, 23 July 1959, Stern et al. 1076 (MO).
Panama Chiriquí: Cerro Punta Region, 1500-2000 m,, 1938, Woodson et al. 882 (MO).
Panama Chiriquí: Cerro Punta Region,, 30 May 1970, Thomas B. Croat 10551 (MO).
Panama Chiriquí: Boquete Region,, 20 July 1971, Thomas B. Croat 15844 (MO).
Panama Chiriquí: Cerro Punta Region, 2000 m,, 7 Aug. 1974, Thomas B. Croat 26427 (MO, SEL).
Panama Chiriquí: Cerro Punta Region, 2000 m,, 7 Aug. 1974, Thomas B. Croat 26494 (B, CM, CAS, DUKE, K, MO).
Panama Chiriquí: Cerro Punta Region,, 20 Feb. 1971, Thomas B. Croat 13618 (MO).
Panama Chiriquí:, 22 July 1971, Croat & Porter 16063 (M, MO, RSA, U, VEN).
Panama Chiriquí: Cerro Horqueta, 1650 m,, 13 Aug. 1974, Thomas B. Croat 26976 (B, CM, CR, F, GH, K, M, MO, NY, PMA, RSA, US).
Panama Chiriquí: Cerro Pate Macho, 1700-2100 m, 8.47N 82.22W, 24 Apr. 1982, Knapp & Schmalzel 4794 (MO, USM).
Panama Chiriquí: 2250-2400 m, 8.50N 82.32W, 9 Nov. 1980, Stevens 18226 (MO, PMA).
Panama Chiriquí: Cerro Punta Region, 1600 m,, 23 Feb. 1974, Nee 9945 (MO).
Panama Chiriquí: Boquete Region,, 21 July 1971, Thomas B. Croat 15743 (MO, NY).
Panama Chiriquí:, 5 June 1979, António 1059 (MO).
Panama Chiriquí: Dtto. Boqute,, 17 Jan 1938, Davidson 225 (MO).
Panama Chiriquí: Dtto. Boqute,, 9 Feb 1938, Davidson 276 (MO).
Panama Chiriquí: Río Chiriquí Viejo, 1300-1900 m,, 1935, Seibert 289 (MO).
Panama Chiriquí: Cerro Horqueta, 1670-1930 m,, 13 Dec. 1966, Burch 553 (MO).
Panama Chiriquí: Cerro Punta, 2000 m,, 25 Nov. 1979, Thomas B. Croat 48568 (K, MO, PMA, SEL).
Panama Chiriquí: Boquete Region, 1800 m,, 8 July 1940, Woodson & Schery 265 (MO).
Panama Chiriquí:, 17 Nov. 1978, Hammel 5667 (MO).
Panama Chiriquí: Cerro La Trompeta, 2070 m,, 25 May 1979, Hammel 7464 (MO).
Panama Chiriquí: Boquete Region, 1500-2500 m,, 21 March 1977, D'Arcy 10853 (MO).
Panama Chiriquí: Boquete Region,, 20 March 1977, Folsom 2194 (MO).
Panama Chiriquí: Cerro Horqueta, 1660-1700 m, 8.49N 82.29W, 1 Jan. 1975, Cochrane et al. 6243 (MO, WIS).
Panama Chiriquí: Cerro Punta Region, 2330 m,, 2 Apr. 1979, Hammel et al. 6623 (MO).
Panama Chiriquí: Cerro Punta Region, 1500-2000 m,, 1938, Woodson et al. 982 (MO).
Panama Chiriquí: Cerro Punta, 2000-2330 m,, 22 Oct. 1977, Folsom 6034 (MO).
Panama Chiriquí: 1730 m, 8.49N 82.28W, 19 February 1986, Scott Hoover 1340 (MO).
Panama Chiriquí: 1630-1780 m, 8.46N 82.25W, 18 June 1987, Croat 66358 (MO).
Panama Chiriquí: 2200 m,, , Correa & Lazor 1407 (PMA). Panama Chiriquí: 1700 m,, , McDaniel 10161 (IBE).
Panama Chiriquí: Cerro Pate Macho, 1500-1700 m, 8.50N 82.25W, 6 January 1983, Bruce A. Stein Bob Schmalzel and David W. Roubik 1183 (MO).