Introduction

The genus Palmorchis Barb.Rodr. was proposed by ^{Barbosa Rodrigues in 1877} to describe two Brazilian species, Palmorchis pubescens Barb.Rodr. and Palmorchis sobralioides Barb.Rodr., possessing a palm-like habit (fide Barbosa Rodrigues, “very similar to Geonoma palm [Arecaceae]”). Currently the genus encompasses 34 species found in Central and South America, including Trinidad (^{Pridgeon et al. 2005}, ^{Szlachetko et al. 2018}). According to ^{Dressler (1993}a,^b), Palmorchis species are terrestrial plants with slender, reed-like stems, several to many, 2-ranked or spiral, pleated leaves; inflorescence is terminal or lateral, of several flowers, usually produced one at a time; sepals and petals are similar, spreading; the slender column is enfolded by the lip and united with it basally along its mid-nerve; and four, soft pollinia.

Palmorchis is one of several poorly known orchid genera of the New World (^{Hágsater et al. 1996}). Plants of this genus look like small palm seedlings or forest grasses and can be easily overlooked when not in flower. Furthermore, the flowers last only a few hours; to find Palmorchis in flower, as ^{Dressler (1984}) noted, “you should be either lucky or persistent”. The taxonomic position of Palmorchis has been a subject of debate since its description (^{Hoehne 1945}, ^{Schweinfurth & Correll 1940}, ^{Szlachetko & Baranow 2014}). Recent molecular phylogenetic studies reveal that Palmorchis is one of the most primitive Epidendroideae, sister to tribe Neottieae (^{Chase et al. 2003}, ^{Rothacker 2007}). However, further studies and sampling are necessary to better assess this evidence.

In Peru, Palmorchis was first recorded in 1928 by Rudolf Mansfeld, who described Neobartlettia lobulata Mansf. [=P. lobulata (Mansf.) C. Schweinf. & Correll] (Figure 1) based on a specimen collected in the eastern part of the country (Loreto). Since then, a few individuals have been recorded, mainly represented by sterile specimens from mixed lowland forest and palm-dominated wetlands (known as aguajales). Until this work, only P. lobulata was reported for the country (^{Brako & Zarucchi 1993}). Nevertheless, a detailed study of available herbarium material reveals a higher diversity of Palmorchis. The present study recognizes six species of Palmorchis for Peru, including one new record and four new species (Figure 2). A taxonomic synopsis, an artificial key, and a map of all known localities for Peruvian Palmorchis are provided in this work, as well as comparative notes with their close relatives.

Materials and methods

For the taxonomic treatment, protologues were obtained from ^{Tropicos (2016)}, names were checked in the ^{IPNI (2016)} database, and currently accepted scientific names and synonyms were based on ^{Govaerts et al. (2016}). Herbarium specimens deposited at USM and AMAZ were revised, as well as high-quality images of herbarium specimens at CUZ, FLAS, AMES, RB, F, US, P, and MO. In August 2016 the first author carried out field work in Peru’s Amazon lowlands in the Department of Loreto. When available, specimens were photographed in situ using a Nikon D7100 with a Micro Nikkor 60-mm lens. Descriptions and measurements were carried out using a Euromex SB-1903 stereomicroscope. Line illustrations were prepared from alcohol-preserved available material, digital photos and rehydrated flowers, and processed with Adobe Photoshop CC v. 14.0.

Taxonomic treatment

Key to the peruvian species of Palmorchis

Plant small, up to 30 cm tall; leaves narrowly elliptic, 3-veined; flowers whiteP. imuyaensis 1a. Plant large, 40-60 cm tall; leaves broadly elliptic to obovate; 5-9 veined; flowers greenish to yellowish 2

Flowers with tepals >2 cm long, narrowly lanceolate; lip with midlobe 9-10 mm long, densely pubescent P. yavarensis

2a. Flowers with tepals <2 cm long, oblong-elliptic to obovate; lip with midlobe <4 mm long, glabrous 3

Inflorescence lateral; lip free from the column, midlobe bilobed; column overall glabrousP. liberolabellata

3a. Inflorescence terminal; lip united to the column by a membrane down the midline, midlobe simple; column densely pubescent 4

Lip obovate, midlobe rounded, callus with 5 thickened keels P. blancae

4a. Lip obtriangular, midlobe oblong to ovate, callus without thickened keels 5

Leaves 17-24 × 7-9 cm midlobe triangular, lateral lobes sparsely pilose, callus subquadrate, cushion-like P. lobulata

5a. Leaves 9-18 × 3-4.9 cm; midlobe oblong, lateral lobes glabrous, 2 fleshy ridges P. loretana

Palmorchis blancae Damián, sp. nov.

TYPE: PERU. Madre de Dios: Tambopata, 15 km E. de Puerto Maldonado, Albergue “Cusco Amazónico”. 5 April 1986. B. Leon & I. Bohorquez 895 (holotype: USM!). Figure 3.

Most similar to P. nitida Dressler, from which it differs by the inflorescence bearing a long basal bract, 8.0 cm long (vs. 3.5-5.0 cm) and the lip distinctly 3-lobed ornamented by 5 prominent keels (vs. shallowly 3-lobed with 7 thickened keels), densely pubescent below the middle with ciliate margins (vs. glabrous lip with entire margins).

Herb up to 55 cm tall. Roots slender, 0.23 cm wide. Stems cane-like, up to 33 cm long, 0.5 cm in diameter, with 4 leaves. Leaves plicate, 5-veined, broadly elliptic, acuminate, cuneate at the base, 15.0-19.0 cm long, 6.0-8.0 cm wide; petiole up to 4 cm long. Inflorescence up to 5 cm long, terminal, few-flowered, with 1 foliaceous bract at base, narrowly lanceolate, acuminate, 8 cm long. Floral bracts 6.0 mm long, 3.0 mm wide, broadly triangular, acute. Peduncle 24 mm long, pedicel and ovary 8 mm long. Dorsal sepal 11 mm long, 1.5-2.0 mm wide, linear-oblanceolate, acute, concave, 5-veined, thickened in the middle. Lateral sepals 10 mm long, 2 mm wide, oblanceolate, oblique, subfalcate, acute, 5-veined. Petals 10 mm long, 2 mm wide, obliquely ligulate-oblanceolate, acute, 7-veined, apical margin slightly erose, thickened on the outer margins. Lip 10 mm long, 4 mm wide when spread; united with the column for about 2 mm; densely pubescent below the middle with ciliate margins, constricted on the apical quarter with 5 main veins running from the base close to the apex, thickened in apical half; the middle lobe 2.5 mm long, 3.0 mm wide, transversely elliptic, rounded, margins crenulate; lateral lobes semicircular. Column pubescent, slender, terete, up to 8 mm long, densely pubescent on the ventral surface below the middle, anther conic, 1 mm long, pollinia ellipsoid, paired, 0.9 mm long, stigma oblong, emergent. Fruit not seen.

Distribution: Endemic to Peru, where it is known from a single collection in the understory of mature lowland forest in easternmost Madre de Dios (Figure 9). Given that the locality is close to the Peru-Bolivia border, it is likely that the species occurs in similar habitat in Pando, Bolivia.

Etymology: Dedicated to Blanca León, who collected the plant that served as the holotype.

P. blancae belongs to a small group of Palmorchis species characterized by the inflorescence subtended by a basal bract, which resembles somewhat a spatha; and lip with 3 to 7 thickened keels (Table 1). Two species exhibit this combination of features: P. nitida and P. fractiflexa Szlach. & Baranow. The latter is easily distinguished by its overall glabrous lip with short pubescence close to the base and entire basal margins (vs. densely pubescent below the middle with conspicuous ciliate margins), constricted below the middle (vs. on the apical quarter), with 3 lamellae reaching the apex, much higher in the midlobe (vs. 5 main veins not reaching the apex, thickened in apical half).

Another similar species is Palmorchis puber (Cogn.) Garay, which differs in the wide obtriangular lip with an obscure middle lobe, and with 2 inconspicuous lamellae below the apex (vs. obovate lip with 5 thickened veins).

Palmorchis imuyaensis^{Dodson & G.A. Romero, Lindleyana 8(4): 197. 1993}

TYPE: ECUADOR. Sucumbios: Laguna de Imuya, October 1991, C.H. Dodson & G.A. Romero 18922 (Holotype: MO ex RPSC, Isotypes: AMES, SEL). Figure 1-2,4.

Palmorchis imuyaensis is most similar to P. puber, but distinguished from the latter in the spathulate lip (vs. obtriangular to obovate-obtriangular) without lamellae on the disc (vs. 2 low lamellae below 3-lobed apex) and conspicuous triangular apex (vs. short, truncate apex).

Distribution: Ecuador and Peru (Figure 4).

Specimens examined: Perú. Loreto: Maynas, Dist. Las Amazonas, Yanayacu, 3°27’46.22”S 72°16’15.06”W, 100 m, 16 August, 2016, A. Damián, N. Mitidieri, R. Cahuachi & M. Segundo 4040 (UFV!).

The Peruvian specimen shows some notable differences from the Ecuadorian type (^{Dodson & Romero-Gonzales 1993}), especially in flower morphology. First, the leaves are shorter and narrower, 13.0 × 1.5 mm (vs. 16.0 × 3.0 mm). The flowers are slightly shorter as well, with sepal dimensions of 8.0- 9.0 × 2.0-3.0 mm (vs. 10.0 × 2.5-3.0 mm). Moreover, the petals and lip are minutely ciliate at the base with a column densely pubescent on the lower part (vs. petals, lip and column glabrous). This species can be distinguished from other Palmorchis species by the small plants, narrower leaves which are 3-veined, flowers white with petals ciliate at the base, column densely pilose, lip margins glabrous and pilose at base (feature presented here), with a V-shaped cavity on the upper side just ahead of the keel, and iridescent blue broadly triangular midlobe (Table 1).

Palmorchis liberolabellata Damián, sp. nov.

TYPE: PERU. Cusco: La Convención, Dist. Echarati, 11°46›53.40»S; 72°42›6.00» W. Bosque colinoso dis- turbado, 400 m. H. Beltrán, W. Nauray, R. De la Colina,

L. Acurio, J. Tenteyo 3204 (holotype USM!). Figure 5.

Palmorchis liberolabellata is similar to P. prospectorum, from which it is easily distinguished by its glabrous floral bracts and flowers (vs. pubescent floral bracts, sepals, lip and column); smaller flowers with sepals 8.5-10.0 mm long (vs. >25.0 mm long); lip free from the column (vs. lip united with the column by a membrane down to the middle of its length), and callus formed by 5 main veins thickened in the upper part (vs. 3 main thickened veins).

Herb at least 40 cm tall. Roots not seen. Stems terete, 0.6 cm in diameter, with 5 leaves toward the apex. Leaves broadly elliptic, plicate, with 5 prominent veins on the underside, petiolate, not articulated to the sheath, oblong-elliptic, acuminate at the apex, cuneate at the base, 37-48 cm long including the petiole, 7-9 cm wide. Inflorescence axillar, 3-6 cm long, many flowered, congested. Peduncle 0.8-1.0 cm long, with 2 ovate bracts close to the base, 1.2-1.5 cm long. Flowers produced one to two at a time, green-yellowish; flowers bracts ovate, acute, glabrous, 1.0-1.5 cm long, 0.3-0.5 cm wide. Pedicel and ovary, 6-8 mm long. Dorsal sepal oblong-elliptic, acute at the apex, 5-veined, 10 mm long, 2 mm wide. Lateral sepals, oblong, obtuse, falcate, slightly erose at the apex, 5-veined, 8 mm long, 2 mm wide. Petals oblong, acute, 8.0-8.5 mm long, 2.0 mm wide, subacute, falcate at the apex, 5-veined. Lip 7.5 mm long, 4.5 mm wide, free from the column, obovate, distinctly 3-lobed near the apex, with 5 veins running from the base of the lamina towards the apex, distinctly thickened below the base of the midlobe, glabrous, midlobe bilobed, lobes broadly rounded, erose, lateral lobes semicircular. Column 10 cm long, terete, slightly arcuate, shortly pubescent on the ventral surface near the base, anther flattened conic, 1 mm long, pollinia ellipsoid, paired, acute, 0.6-0.8 mm long, stigma transversely oblong, emergent. Fruit not seen.

Distribution: Endemic to Peru, where it is known only from the type locality in the understory of bamboo- dominated lowland forest in the department of Cusco (Figure 9).

Etymology: The epithet refers to the free lip from the column, an atypical feature among the genus.

Among the Palmorchis species with lateral inflorescences and bilobulate midlobe lips, P. liberolabellata is easily distinguished by its combination of glabrous floral bracts and lip, the latter also free from the column and bearing 5 thickened keels on the disk (Table 1).

Although P. prospectorum Veyret might be the closest relative to P. liberolabellata, it differs notably in its larger flowers and 3-veined thickened lip densely pubescent that is united to the column almost to its middle length. In addition, P. prospectorum is endemic to French Guiana and Surinam, where it grows as terrestrial herb in swamp forest, while P. liberolabellata has been reported from southeastern Peru, in the lowlands of Cusco, growing in a disturbed ‘pacal’ forest dominated by the bamboo Guadua sarcocarpa (Poaceae).

Palmorchis deceptoria Veyret & Szlach. and P. powellii (Ames) C.Schweinf. & Correll also possess the main features of the informal group of Palmorchis species described above. However, both can be distinguished from P. liberolabellata by the densely pubescent subtrilobed lip with not well-defined lateral lobes. The disc of the lip of P. powellii is similar to the one found on P. liberolabellata, bearing 5 long thickened veins. However, on P. powellii the middle vein extends to the apex of the midlobe, while in P. liberolabellata the main veins are only thickened close to the middle of the lamina, and none reach the midlobe. On the other hand, P. deceptoria presents 3 long thickened veins that are congested along the midvein, while P. powellii and P. liberolabellata bear 5 spreading thickened veins. Palmorchis deceptoria is believed to be endemic to Colombia, where it has been recorded near the Caunapi River, probably in swamp forest, while P. powellii is native to Mesoamerica (Costa Rica, Panama), where it grows in damp places with dense shade.

Palmorchis lobulata (Mansf.) C.Schweinf. & Correll, Botanical Museum Leaflets 8:113. (1940: 113). Neobarlettia lobulata^{Mansfeld (1928}: 237).

TYPE: PERU. Loreto: Cuenca del Marañón, desde Iq- uitos hasta el Estuario Santiago en el Pongo de Mans- eriche, 160 m. 11 November 1924. G. Tessmann 4518 (holotype: B, destroyed, lectotype AMES!, selected by ^{Szlachetko et al. 2018}). Figure 6.

Palmorchis lobulata is most similar to P. guianensis (Schltr.) C.Schweinf. & Correll, from which it differs in having broader leaves, 4.7-9.0 cm wide (vs. 3.5-4.0 cm), lip with pilose margins in front (vs. glabrous, entire margins), lateral lobes rounded to truncate (vs. obtuse to rounded), subquadrate cushion-like callus and midlobe small, triangular (vs. narrower midlobe with an axial thickening and globose termination).

Distribution: Colombia, Ecuador and Peru (Figure 9).

Additional Specimens Examined: Peru. Huanuco: Pachitea, Dtto. Honoria, Bosque Nacional de Iparia, 300-400 m, 21 February 1967, J. Schunke 1652 F (photo)!; Loreto: Dist. Alto Nanay, Santa María de Nanay, Trocha a piusco, 130 m, 9 March 1968, J. Schunke 2517 F (photo)!; Ucayali: Prov. Coronel Portillo, Dist. Iparia. Bosque nacional de Iparia: región de bosque seco tropical a lo largo del río Ucayali cerca del pueblo de Iparia (unos 80 km. arriba de la confluencia con el río Pachitea), 300 m, 26 agosto 1968, J. Schunke 2693 F (photo!); Prov. Purús, Dist. Purús, cuenca del rio Curanka, afluente del río Alto Purús, cerca de la comunidad Nativa Colombiana. 11

According to the key presented by ^{Szlachetko & Baranow (2014}) and the description and illustration published by ^{Dodson & Dodson (1980}), the lip midlobe of P. lobulata is truncate. However, this disagrees with the original description (it states: ¨lobo medio brevi triangulari”), the detailed flower drawing of the holotype by L. Garay (AMES) and its treatment for Ecuador (^{Garay 1978}), as well with the work of ^{Schweinfurth & Correll (1940}) which proved that the lip of this species is actually triangular.

Peruvian specimens of P. lobulata are scarce, usually infertile and with several misidentifications. We did our best to gather all the specimens available of this species and we include only those with flowers present. However, several specimens revised were fruiting or with immature buds, making them impossible to study rigorously. We managed to dissect a couple of flowers (Graham & Schunke 809) and some difference between the type and the latter specimen are noticeable. First, the leaves are shorter, 10.0-4.7 cm (vs. 24.0 × 9.0 cm). Moreover, the flowers are slighter smaller as well, 11.0-13.0 × 2.5-3.0 (vs. 8.0-9.0 × 2.5- 3.0). Finally, the lateral lobes are distinctly truncate with a small triangular midlobe which is pilose and has a low midvein that is thickened (vs. lateral lobes rounded, more or less truncate, midlobe glabrous without thickened veins) (Table 1).

Palmorchis loretana Damián & Torrres, sp. nov.

TYPE: PERU: Loreto: Requena, Dist. Soplín, quebra- da Yanayacu-Río Blanco. Campamento Wiswincho, 05°48’36.00”S 73°51’56.00”W, 10 October 2014. M.

Ríos, T. Mori, N. Pitman, L. Torres & C. Vriesendorp 4268 (holotype: AMAZ!). Figure 7.

Palmorchis loretana is most similar to P. sobralioides, from which it differs in its smaller flowers, tepals 5-8 mm long (vs. tepals 20 mm long); densely pubescent lip below the middle (vs. glabrous); midlobe oblong, acute, with three low thickened keels (vs. triangular-ovate, obtuse, without keels) and callus with two fleshy tall ridges (vs. four elevated, small, protuberances).

Terrestrial herb, 40-50 cm tall. Roots not seen. Stems cane-like, up to 16 cm long, 0.25 cm in diameter, with 4 leaves towards the apex. Leaves light green, plicate, with 5 prominent veins on the underside, oblong-elliptic, acuminate at the apex, narrowing to the junction with the petiole, 9.0-18.0 cm long and 3.0-4.9 cm wide; petiole up to 1.5 cm long. Inflorescence up to 4.5 cm long, terminal, few-flowered. Floral bracts 12- 19 mm long, narrowly triangular, acuminate, pedicel and ovary 5 mm long. Flowers pale yellowish-green, small. Dorsal sepal 6-8 mm long, 1 mm wide, oblong- elliptic, acute, concave, 5-nerved. Lateral sepals 6-8 mm long, 1 mm wide, oblanceolate, oblique, subfalcate, acuminate, central nerved thickened externally, 5-nerved. Petals 5-8 mm long, 1 mm wide, obliquely oblanceolate to oblong-oblanceolate, acute, obscurely 5-nerved. Lip 5-8 mm long, 3 mm wide when spread, narrowly obtriangular, 3-lobed at the apex; united with the column at its base for about 1 mm; base of the lip densely pubescent and spread along the main axis up to the middle of the lip; callus with two parallel, approximate fleshy ridges, upcurved apically; midlobe of the lip with three conspicuous thickened keels. Column pubescent, slender, terete, up to 4.5-8.0 mm long; anther flattened subconic, 1.5 mm long, pollinia ellipsoid, subacute, 0.8-1.0 mm long, stigma transversely oblong, emergent. Fruit not seen.

Paratype: PERU. Loreto: Putumayo, Dist. Yaguas,

Inventario Rápido de la cuenca del río Yaguas. NE de Iquitos y Pebas en las esquinas del trapezoide de Colombia. Drenaje del bajo Putumayo. En la boca de la quebrada Cachimbo, tributario S del bajo Yaguas, a 44 km O de la unión Yaguas-Putumayo. 02°43’42.8’’S 70°31’31.7’’W. Bosque de planicie inundable. 94 m. 27 October 2010. I. Huamantupa, Z.Cordero, N.Pitman &

R. Garcia 14698B (AMAZ!)

Etymology: In reference to the Peruvian Department of Loreto, where the type specimen was collected.

Distribution: Endemic to Amazonian Peru, where it is known from two localities in the department of Loreto, at altitudes between 90-100 m in the Yaguas and Tapiche watersheds. At both localities the species was recorded growing in the understory of floodplain forest on relatively poor soils (Figure 9; ^{García Villacorta et al. 2011}, ^{Torres Montenegro et al. 2015}). These sites are relatively close to the Colombian and Brazilian borders, and the species likely occurs in similar habitat in those countries.

Additional Specimens Examined: ECUADOR. Napo: Yasuni river. 30 min. upstream from Garzacocha.

Primary rain forest. Terra firme. Alt. 200 m. 01°03’0.00”S 75°28’12.00”W, 11 April, 1983. J. E.

Lawesson, T.Lassoe & P. M. Jorgensen 43445 (AAU!). BRASIL, Est. do Pará, Mpio. Faro, 06/01/1920. A. Ducke 14663 BR!); Est. do Amazonas, Mpio. Manaus, Reserva Forestal Ducke, Kinupp, V.F. & Pereira F.N. 2015 (210109 INPA!).

As the diagnosis states, P. loretana is quite similar to the poorly known P. sobralioides. Although minimal, the prologue of this latter species by ^{Barbosa Rodrigues (1877}) and later, the extended version of ^{Cogniaux (1893}) including Barbosa’s drawings, are clear enough to differentiate it from P. loretana. Both authors indicate in their description of the early species a 3-lobed lip, with broad lateral lobes and a minute, ovate-triangular, acute midlobe, with four small protuberances. In contrast, P. loretana has a conspicuous oblong, acute midlobe with three low keels, and callus bearing two tall parallel ridges (Table 1). In addition, P. sobralioides is known to have a glabrous column while P. loretana is densely pubescent on the ventral surface.

Another important difference between these two species lies in their distribution. Palmorchis species are in the great majority restricted in range, with some notable exceptions like P. silvicola L.O.Williams and P. powellii, which disjunctions reported from Costa Rica to Ecuador and Colombia. A comprehensive study is needed in order to corroborate the South American populations. For example, we studied an Ecuadorian specimen cited as P. sobralioides (Lawesson et al. 43445, AAU!). A close look at the plant, which has the combination of narrower 3-veined leaves, (1.0-1.5 cm wide) and blue flower lip, pointed us to P. imuyaensis, whose holotype was found not far away (Imuya, Sucumbíos). Specimens of P. sobralioides are known from Pará and Manaus (Brazil), while P. loretana seems to be endemic to the northeastern lowland forest of the Peruvian Amazon (Loreto). We were able to compare photos of the flowers of our plant and P. sobralioides (^{Ribeiro et al. 1999}, 210109 INPA). Flowers of the latter look robust, with a tiny midlobe lip bearing 4 obscure protuberances and some blue color at the midlobe of the lip, a feature not reported before (vs. slender flowers, long midlobe and purple colored midlobe of P. loretana).

Palmorchis yavarensis Damián & Torres, sp. nov.

TYPE: PERU. Loreto: Mariscal Ramón Castilla, Dist. Yavarí, margen izquierda del río Yavarí, entre Colonia Angamos y Lago Preto, Quebrada Limera, 04°30’53.37”S, 71°54’2.77”W 9 April 2003, H. Bel-trán, R. Foster, N. Pitman, R. García, C. Vriesendorp & M. Ahuite 5698 (holotype: USM!, isotypes: F!, AMAZ!). Figure 8.

Palmorchis yavarensis is most similar to P. maguirrei Szlach., S.Nowak & Baranow, from which it is distinguished by its glabrous bracts (vs. pubescent); linear-lanceolate glabrous sepals with acuminate apex, 27-30 × 2-3 mm, (vs. oblong, acute and pubescent along adaxial midvein, 21 × 4 mm); and distinctly 3-lobed lip, scarcely pubescent, with ciliate margins and 3 thickened main veins from the base to near the middle of the midlobe (vs. subtrilobed, with entire margins, pubescent along the midvein, and a single thick ridge along midvein).

Herb 60 cm tall. Roots not seen. Stems cane-like, 0.8 cm in diameter, with 8 leaves. Leaves plicate, 5-7-veined, broadly elliptic to obovate, acuminate, cuneate at the base, 65-70 cm long including the petiole, 10-11 cm wide. Inflorescence terminal, 8.0-9.7 cm long, many-flowered. Peduncle 6.0-7.5 cm long, with 1-2 lanceolate bracts. Flowers yellowish, simultaneous. Floral bracts 16.0-17.5 cm long, triangular, acuminate. Pedicel and ovary 9-12 mm long. Sepals similar, 27-30 mm long, 2-3 mm wide, linear-lanceolate, acuminate, obscurely 7-veined. Petals 22-25 mm long, 2 mm wide, linear-lanceolate, acuminate, 5-veined. Lip 23-25 mm long, 8 mm wide; distinctly 3-lobed; united to the column for 1.0-1.5 mm; sparsely pubescent all over, especially at the base and along the middle of the lamina, the margins ciliate, with 3 thickened main veins running from the base to near the middle of the midlobe; middle lobe 9-10 mm long, narrowly ligulate, acute, densely pubescent, recurved, margins undulate, upper part with a distinct longitudinal furrow; lateral lobes obliquely triangular-ovate, broadly obtuse. Column slender, terete, 15 mm long, densely pubescent below the stigma. Anther sub-conic, 1.5 mm long, pollinia ellipsoid, paired, 1 mm long, stigma transversely oblong; fruit not seen.

Paratypes: PERU. Loreto: Putumayo, Dist. Yaguas, NE de Iquitos y Pebas, en la esquina del trapezoide de Colombia. Drenaje del Bajo Putumayo. Quebrada Lupuna, tributario N del medio Yaguas, Bosque colinoso de tierra firme, 2°36’38.20”S 71°29’8.70”W. 161 m, 15 octubre 2010. I. Huamantupa, Z. Cordero, N. Pitman & R. Garcia 14065 (AMAZ); Ucayali: Padre Abad, Dist. Padre Abad, Carretera al caserio San Miguel y Mapuya, 12 a 17 km de la Aguaytía, 09°05’00.0”S 75°26’00.0”W, 350 m, 10 August 2004, J. Schunke & J. G. Graham 16290 F!.

Etymology: The new species was named after Yavarí, a proposed reserved Zone in Loreto, highlighting that the first records were made there.

Distribution: Endemic to Peru, where it is known from two localities in Loreto (Yavarí and Yaguas watersheds) and one in Ucayali (Ucayali watershed). All known specimens were collected in the understory of mature lowland forest. The Loreto localities are very close to the Brazilian and Colombian borders; the species is likely to occur in similar habitat in those countries (Figure 9).

Palmorchis yavarensis belongs to a small complex of species characterized by robust plants with large leaves and a distinct narrow acuminate lip (Table 1). Two members of the complex are P. carlos-parrae Szlach. & Baranow and P. maguirrei, from which P. yavarensis differs in its glabrous bracts and lip morphology. Palmorchis carlos-parrae from Colombia has the largest flowers of the genus with sepals 32 mm long and lip 26 mm long, entire and glabrous with a broad midlobe, 4 mm wide. Palmorchis yavarensis, on the other hand, has sepals and lip up to 30 and 25 mm long respectively, the lip is scarcely pubescent, especially along the middle of the lamina, and the midlobe is 1.5 mm wide. Moreover P. yavarensis has obliquely triangular-ovate lateral lobes with ciliate margins, while P. carlos-parrae presents falcate, acute entire lateral lobes.

This species was first reported as “Palmorchis sp.” by ^{Pitman et al. (2003}) on a rapid biological inventory of the Yavarí river valley in the Amazonian lowlands of northeastern Peru (Loreto). Later that year, ^{Foster et al. (2003}) published a rapid color guide including a photograph of this species, in which its yellowish big flowers and large lip are clearly visible (Figure 2A).

After almost a decade, the species was found again in the same department, this time in the headwaters of the Yaguas River, close to the Peru-Colombia border (^{García-Villacorta et al. 2011}). We were unable to dissect the flowers of this plant. However, the detailed photos provided by the collector are sufficient evidence to place this specimen in the concept of P. yavarensis.