Epiphyte; stems 1-1.5 cm diam.; roots few, descending, 2-3 mm diam.; cataphylls moderately thin, 2-3 cm long, acuminate at apex, drying brown, weathering into fibers, subpersistent.

LEAVES erect; petioles 4-26 cm long, 5-6 mm wide, triangular, sulcate, drying with a narrow, almost membranous wing; gcniculum 0.5-1.2 cm long; blades lanceolate-elliptic, acuminate at apex, obtuse to rounded at base, 15-23.5 cm long, 6-10 cm wide, broadest below the middle, obscurely and sparsely punctate above, densely punctate below, the punclalions reddish-brown, the margin drying conspicuously undulate; lower surface paler than upper; primary lateral veins 10-20 per side, departing midrib at 5 5° angle, almost straight to collective vein; interprimary veins numerous; collective vein arising from the base, 3-8 mm from margin.

INFLORESCENCE shorter than leaves; peduncle 12-19 cm long, ca. 3 mm wide, winged, 0.5 to 5 times longer than petioles; spathe green suffused with purple-red at margin, lanceolate-linear, 3-4.5 cm long, 6-8 mm wide, broadest at base, short-acuminate at apex (the acumen apiculate), inserted at ca. 30° angle on peduncle; spadix sessile, green, 10-12 cm long, 3-5 mm diam. at base, 2-3 mm diam. at apex; flowers rhombic, 2,3-2.8 mm long (dry), 1.8-2.3 mm wide (dry), the sides ± straight to weakly sigmoid; 4-5 flowers visible in the principal spiral, 3-5 flowers visible in the alternate spiral; tepals drying matte, the lateral tepals ca. 2 mm wide (dry), the inner margins broadly rounded; stamens emerging just above the tepals, the anthers ca. 0.4 mm long, 0.9 mm wide (dry); thecae strongly divaricate.

INFRUCTESCENCE not seen. Fig. 5.

The species is known only from the Osa Península in tropical wet forest at less than 100 m elevation.
Anthurium alatipedunculatum is most closely allied to A. acutangulum but differs in having a winged, angulate peduncle and a triangular petiole which is sharply sulcate adaxially. The species is a member of section Porphyrochitonium.

Map of Mesoamerican specimens with coordinates

Costa Rica Puntarenas: Parque Nacional Corcovado, 745 m, 08.31.30N 83.28.00W, 3 Aug 1990, Herrera 4108 (CR, MO, CR).
Costa Rica Puntarenas: 150-260 m, 8.41N 83.32W, 3 March 1985, T.B. Croat & M.H. Grayum 59772 (MO).
Costa Rica Puntarenas:, , Utley & Utley 1030 (F, MO).
Costa Rica Puntarenas: Río Madrigal, 300 m, 08.29.30N 83.29.10W, 3 Dec 1990, Herrera 4695 (MO).
Costa Rica Puntarenas: Rincón, 350 m, 08.42.50N 83.31.42W, 17 July 1990, Herrera 4277 (MO, CR).
Costa Rica Puntarenas: 500 m, 8.43N 83.32W, 2 Oct. 1990, Herrera 4441 (MO, CR).
Costa Rica Puntarenas: R.F. Golfo Dulce; Península de Osa, 200-450 m, 08.42.00N 83.35.40W, 15 November 1993, Barry Hammel & Reinaldo Aguilar 19125 (CR).
Costa Rica Puntarenas: P.N. Corcovado; Península de Osa, 10 m, 08.28N 83.35W, 11 October 1993, Reinaldo Aguilar 2458 (CR).
Costa Rica Puntarenas: R.F. Golfo Dulce; Península de Osa, 400 m, 08.41.50N 83.35.40W, 20 June 1990, Gerardo Herrera 4215 (CR).
Costa Rica Puntarenas: R.F. Golfo Dulce; Península de Osa, 744 m, 08.30.15N 83.28.20W, 27 November 1990, Gerardo Herrera 4655 (CR).
Costa Rica Puntarenas: P.N. Corcovado; Península de Osa, 600 m, 08.29.50N 83.28.55W, 8 December 1990, Gerardo Herrera 4743 (CR).
Costa Rica Puntarenas: R.F. Golfo Dulce; Península de Osa, 200 m, 08.45.15N 83.23.35W, 14 December 1990, Gerardo Herrera 4778 (CR).
Costa Rica Puntarenas: R.F. Golfo Dulce; Península de Osa, 500 m, 08.42.50N 83.32.10W, 17 December 1990, Gerardo Herrera 4796 (CR).
Costa Rica Puntarenas: R.F. Golfo Dulce; Península de Osa, 300 m, 08.42.00N 83.35.40W, 13 January 1993, Barry Hammel, R. Aguilar & A. Gentry 18728 (CR).
Costa Rica Puntarenas: 200-300 m, 08.42.00N 83.12.30W, 12 September 1996, Thomas B. Croat & Dylan Hannon 79287 (B, K, MO, WU).
Costa Rica Puntarenas: Las Cruces Biological Station, 1275 m, 08.47.08N 82.57.29W, 4 July 1994, Kress, W. & V. Di Stilio 94-4108 (CR).
Costa Rica San José: 1800 m, 09.29.20N 083.49.35W, 11 Dec. 1994, Herrera, G. et al. 7456 (MO).