LEAVES pendent; petioles 30-35 cm long, 6-8 mm diam., terete, sulcate; geniculum 1-1.2 cm long; blades strap-shaped, gradually long-acuminate at apex, narrowly acute at base, 1 OS-142 cm long, 8-10 cm wide, broadest near the middle; midrib prominently raised above to very near the apex, raised below; primary lateral veins numerous, departing midrib at ca. 55° angle, scarcely or not at all distinguishable from the interprimary veins on upper surface, only slightly more prominent on lower surface; interprimary veins usually numerous; collective vein arising from near the base, 3-4 mm from margin throughout.

INFLORESCENCE pendent: peduncle to 39 cm long, ca. 4 mm diam., slightly longer than petioles; spathe medium thick, pale green, spreading, lanceolate-linear, to 29 cm long, ca. 1.5 cm wide, broadest near base, acuminate at apex, acute at base, inserted at 70° angle on peduncle; spadix brown (fide label), to 60 cm long, 7-8 mm diam. at base, ca. 4 mm diam. at apex; the flowers (dry) rhombic, 3.4-4.5 mm long, 1.8-2.2 mm wide, the sides jaggedly sigmoid; 5-6 flowers visible in the principal spiral, 7-8 flowers visible in the alternate spiral; tepals smooth, the lateral tepals 2-2.5 mm wide, the inner margin convex; the pistil green, ca. 1 mm long, ca. 0.8 mm wide, emerging evenly throughout; the stigma ca. 0.7 mm long (dry), oblong; stamens perhaps only partly exserted above the tepals (at least partly retracted on drying).

INFRUCTESCENCE pendent; berries probably orange. Figs. 146 and 147.

Anthurium prolatum is known only from northern Costa Rica in Alajuela and Heredia Provinces in tropical wet forest at 200 to 600 m elevation.

The species is a member of the section Pachyneurium and can be distinguished by the unusual, very long and narrow leaves, cataphylls, spadix, and spathe. It is most easily confused with A. protensum, however, A. prolatum differs from that species by having its spadix more than twice as long as any observed for even the largest A. protensum, a spathe considerably more narrow and lacking the purple markings characteristic of A. protensum, and the flowers twice as long (0.5-2.5 mm long in A. protensum, 3.4-4.5 mm long in A. prolatum). In addition, the common A. protensum has not been collected below 1,000 m and is most common at 1,800 m elevation.

Map of Mesoamerican specimens with coordinates

Costa Rica Alajuela: 600 m,, 3 Feb. 1979, Thomas B. Croat 46979 (MO). Costa Rica Cartago:, 5 Feb. 1979, Thomas B. Croat 47087 (MO)
Costa Rica Heredia:, , Lent 2140 (F).
Costa Rica Lim—n: Lago Dabagri, 1000 m, 09.38N 83.18W, 1984, Gomez et al. 23155 (B, K, MO).
Costa Rica Lim—n: 400 m,, 18 July 1964, Jimenez 2113 (F).
Costa Rica Lim—n: Cordillera de Talamanca, 1200-1300 m, 09.45N 83.19W, 16 Aug 1995, Grayum 11024 (CR, INB, MO).
Costa Rica San José: 400-1500 m, 10.05N 84.58W, 28 Jul 1985, B. Hammel & J. Trainer 14266 (MO).
Panama Bocas del Toro: 850 m, 08.48N 82.13W, 29 March 1993, Thomas B. Croat 74924 (MO).
Panama Bocas del Toro: Fortuna Dam Area, 550-650 m, 8.48N 82.10W, 30 April 1986, Gordon McPherson 9154 (MO).
Panama Bocas del Toro: 770 m, 08.45N 82.17W, 27 June 1994, Thomas B. Croat & Guanghua Zhu 76532 (CAS, MEXU, WU, MO, NY, U).