Autana andersonii C. T. Philbrick, gen. et sp. nov. TYPE: Venezuela, Amazonas: Rio Autana, 4.7660°N, 67.4567°W, 60 m, 5 Jan. 2006, C. T. Philbrick, A. Novelo R. & C. Lasso 5862 (holotype, VEN; isotypes, CAR, MO, WCSU).

Genus novum Apinagiae Tul. simile, sed ab ea caulibus applanatis supra cristulis anastomosantibus e foliorum marginibus oriundis instructis, apicibus pedicellorum inflatis cavisque et staminum caducorum ad receptaculum locis insertionis fuscatis obovoideisque differt.

Aquatic herbs, presumed perennial, attached to rocks in river rapids and waterfalls; roots not seen; stems prostrate or upright, the flattened stems repeatedly dichotomously or subdichotomously branched, (4-) 12 (-39) X (1.5-) 4 (-15) mm, with anastomosing pattern on upper surface derived from fused petiole margins, anastomosing pattern darkened and obscured as stem dries; the upright stems oval to slightly flattened. Leaves marginal on stems, to 3 m long, distichous, dithecous, bipinnately compound, circinate, petiolate; petioles (1.8-) 9.8 (- 36.8) cm, oval to flattened when young, oval to terete at maturity, gradually tapering apically; petiole margins with membranous stipules when young, quickly falling, margins of adjacent leaf petioles fused, forming darkened, slightly raised ridges that form an anasto mosing pattern on the stem; each pinna with 3 or 4 pinnules; petiolules (2-) 15.5 (-82) mm; pinnae at base of leaf (1.5-) 5.5(— 25.6) mm long, near middle of leaf (0.5-) 4.3 (- 21.1) mm, near apex of leaf (0.5-)2.4- mm; ultimate leaf divisions terete, (0.1-) 0.6 (-2.6) mm X (20-) 60 (-140) µm, arising alternately along central axis or dichotomously-subdichotomously divided. Flowers numerous, marginal or submarginal on the flattened stems, arising solitary in pockets between leaf bases, hermaphroditic, actinomorphic, oriented vertically, pedicellate; pedicels in pre-anthesal flowers (1.2-) 5.2 (-22) mm long; covered  by saclike spathellae, the spathella (3.6-)7.6(-12) X (1.1-)1.8(-2) mm, clavate, smooth, rupturing apically or subapically into 2 to 5 segments as pedicels elongate during anthesis. Tepals (5 -) 7 (- 9), (0.6-) 2.1 (-2.9) mm, arising between stamen filaments, linear, acute. Stamens in complete whorl around ovary, (5-) 7 (- 9), anthers triangular, (0.7-) 1.7 (-2.2) X (0.3-) 0.5 (-0.7) mm at base, introrse, the thecae apices fused; filaments flattened to oval in cross section, attaching to anther in a pocket-like area, widest at base, (0.5-) 1.8 (-2.4) mm in post-anthesal flowers; pollen tricolpate, polar axis (15-) 19 (-22) |µm wide; ovaries (1.2-) 2.2 (-2.6) X (0.6-) 1.3 (-1.9) mm, globose, with a medial longitudi nal line from base to apex; stigmas 2, (0.1-) 0.4 (-0.9) mm, linear, widest at base, fused for most of length, distinct apically for < 0.2 mm, falling after anthesis. Capsules (1.3-) 3 (-4.1) X (1.1-)1.4(-1.9) mm, slightly flattened perpendicular to suture margin, valves 2, persistent, each with 5 non-suture ribs, suture margins also rib-like, pedicellate; pedicels (0.4-) 3.9 (- 5.8) cm X (0.6-) l.l (-1.4) mm, hollow at maturity, apex (receptacle) swollen and hollow, swollen portion extending (1.2-) 4 (-8) mm down pedicel, inverted teardrop-shaped recessed marks (or holes) where stamen filaments attached on swollen pedicel apex (0.2-) 0.6 (-1) X (0.1-) 0.2 (-0.3) mm; seeds (53-) 103(-169) per capsule, (0.2-) 0.3 (-0.4) X (0.1-) 0.2 (-0.03) mm, orange to brown, obovate.

Etymology. The genus name is taken from the Autana River, Amazonas, Venezuela, where the species was first collected (cf. Art. 20.1, McNeill et al., 2006). The specific epithet is in honor of Gregory J. Anderson (1944-), University of Connecticut, who played a central role in the professional development of the first author.

Distribution and IUCN Red List category. Autana andersonii is known from four rivers that drain into the Orinoco River (Fig. 2). The species is common where it occurs. The extent of occurrence (IUCN, 2009) of the species is estimated at 5400 km². The species is categorized as Vulnerable (VUAlcBl), using the IUCN Red List criteria (IUCN, 2009). Factors that make species of Podostemaceae particularly vulnerable to human impacts are discussed in Philbrick et al. (2010).

Paratypes.  VENEZUELA. Amazonas: Río Autana, 4.8022°N, 67.4861°W, 60 m, 4 Jan. 2006, Philbrick, Novelo & Lasso 5860, 5861 (CAR, MO, VEN, WCSU); Río Sipapo, 4.8155°N, 67.7293°W, 6 Jan. 2006, Philbrick, Novelo & Lasso 5863 (CAR, MO, VEN, WCSU); Río Cuao, Raudal del Dante, 5.0442°N, 67.5605°W, 6 Jan. 2006, Philbrick, Novelo & Lasso 5867 (CAR. MO, VEN, WCSU); Río Cuao, Raudal del Dante, 5.0442°N, 67.5605 Jan. 1949, Maguire & Politi 28400 (NY); Puerto Ayacucho, Río Cataniapo, ca. 15 km E of main rd., 5.5548°N, 67.4856°W, 9 Jan. 2006, Philbrick, Novelo & Lasso 5878 (CAR, MO, VEIN, WCSU); Puerto Ayacucho, Río Cataniapo, at bridge along rd. to Samariapo, 5.6034°N, 67.5937°W, 9 Jan. 2006, Philbrick, Novelo & Lasso 5875 (CAR, MO, VEN, WCSU); Canyo Marieta, ca. 1 hr. by boat upstream of confluence with Río Ventuari, 5.1687°N, 66.5334°W, 8 Mar. 2009, Philbrick, Fort & Perrez 6318 (VEN, WCSU).