taxonID	type	description	language	source
B71587ABFFFF263CFF70D440FD49F83A.taxon	materials_examined	Type: — PERU. Pasco: Oxapampa, Huancabamba, Lanturachi, sector Santa Barbara, alrededor del campamento a Milpo, antiguo camino a Santa Bárbara, 3000 m, 22 October 2003, J. Perea et al. 890 (holotype: HOXA 07282!).	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
B71587ABFFFF263CFF70D440FD49F83A.taxon	diagnosis	Pleurothallis yanesha is similar to P. sijmii Luer, but differs in the flowers with the sepals apically connivent (vs. partially spreading), the oblong-triangular dorsal sepal, 37 – 41 mm long (vs. narrowly ovate, 24.5 – 30 mm long), lateral sepals totally connate in a synsepal 35 – 42 mm long (vs. partially or completely connate, 21 – 28 mm long), narrowly ovate petals, 62 mm long (vs. obovate, 23 – 29 mm long), smaller lip (9.6 – 9.7 × 5.6 mm vs. 13 – 14 × 8 mm), without callus (vs. broadly ovate callus), and narrowly triangular, densely papillose, acute mid lobe (vs. oblong, papillose-spiculate, obtuse).	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
B71587ABFFFF263CFF70D440FD49F83A.taxon	description	Description: — Plant epiphytic or rarely terrestrial, caespitose, up to 50 cm high. Ramicauls erect, stout, terete, dark green to brown, 25 – 38 cm long; enclosed by 1 – 2 brown, tubular sheaths, located at the base and in the middle of the ramicaul. Leaves sessile, suberect to spreading, coriaceous, lanceolate, acute, dark green, 12.2 – 19.5 × 3.0 cm; cuneate and conduplicate at the base. Inflorescence arising from a 2.6 – 3.3 cm long spathe, at the base of the leaf, with multiflowered successive, erect to horizontal, loose, secund coflorescences, 1 – 2 developing at a time, simultaneously with up to 15 successive flowers, to 30 cm long, including the pseudopeduncle 15 cm long. Floral bracts tubular, acute, 8.5 × 10.0 mm; pedicels terete, 9.0 – 11.0 mm long. Ovary terete, sulcate, green, 6.0 – 10.0 mm long. Flowers with yellow sepals, spotted and mottled red, especially on the adaxial side, petals greenish-yellow, suffused with red at basal margins, lip white, yellow in the apical half, suffused with red on the lateral lobes, column white, greenish in apical third, anther cap white, with a greenish-yellow spot, pollinia fulvous. Sepals concave, adaxially verruculous, apically connivent; dorsal sepal oblong-triangular, involute, 3 - veined, acuminate, apex progressively contracted into a incurved, linear, acute tail, 37 – 41 × 6.0 – 7.0 mm; lateral sepals connate into a narrowly ovate, slightly constricted in the basal third, acuminate synsepal, 6 - veined, apex progressively contracted into a incurved, linear, acute tail, 35 – 42 × 7.0 – 8.0 mm; strongly involute from the basal third, with an abaxial keel along the junction of the sepal joints. Petals facing forward, slightly oblique, narrowly ovate, 3 - veined, acuminate, 11 – 12 × 4.7 – 5.0 mm, apex progressively contracted into long, recurved, filiform, acute tail, up to 50 mm long, with small verrucae on the apical half and base of the tail, total length 62 mm long. Lip attached to the column, 3 - lobed, 3 - veined, 9.6 – 9.7 × 5.6 mm when expanded, without glenion or callus; lamina with two parallel keels originating in the center of the lateral lobes and disappearing over the lateral veins, in the middle of the mid-lobe; the surface of the lip is covered by sinuous ridges, which are distributed along the longitudinal center of the lip, from the base of the lip to the mid-lobe, the ridges at the base are more scattered, but they cluster distally at the base of the middle lobe, forming a densely papillose apex; lateral lobes erect in natural position, semi-orbicular, ca. 4 × 2 mm; mid-lobe narrowly triangular, acute, 4.4. × 2.4 mm. Column strongly arcuate, claviform, ventrally complanate, with two rounded wings at apex, projecting toward the base, giving it a channeled appearance, minutely ciliate at the base, 6.0 – 6.5 mm long; foot of column very short. Anther subapical, anther cap cucullate, hirsute on top, 2 - celled, 1 × 1 mm; stigma ventral, reniform. Pollinia 2, narrowly obovoid, complanate, ca. 0.6 mm long. Capsule not seen.	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
B71587ABFFFF263CFF70D440FD49F83A.taxon	distribution	Distribution and ecology: — Currently, the species is known from only three localities, two of them located in the districts of Huancabamba [L. Valenzuela et al. 13849 (HOXA) and J. Perea et al. 890 (MO)] and Chontabamba [L. Valenzuela & A. Peña 13880 (HOXA)] between 2000 - 3000 m elevation, in the province of Oxapampa, Pasco department (Figure 5). These localities are located within the Oxapampa-Asháninka-Yánesha Biosphere Reserve (BIOAY), which is characterized by montane forests that form an immense strip of vegetation. These ecosystems are mostly humid, shaded, with rugged topography and basically white sandy soil, with frequent rainfall in all seasons of the year, accompanied by continuous fog and variable temperatures, ranging from warm, temperate, cold, and even very cold, with significant differences throughout the year (Catchpole 2004, Valenzuela-Gamarra et al. 2022). Pleurothallis yanesha grows as an epiphytic or rarely terrestrial (Figure 6), forming small colonies of 4 – 6 individuals, sharing its habitat with other plant species, mainly trees such as Clusia alata Planchón & Triana (1860: 361), Clusia trochiformis Vesque (1893: 49), Escallonia myrtilloides Linnaeus (1781: 156), Ocotea pajonalis van der Werff (2013: 354), Posoqueria coriacea Martens & Galeotti (1844: 240), Saracha punctata Ruiz & Pavón (1799: 42), Symplocos nana Brand (1901: 76), in sympatry with other orchid species such as Epidendrum geminiochraceum Hágsater, Santiago & Medina (2019: 1725), Scaphosepalum atropurpureum Valenzuela (2015: 339), Sobralia caloglossa Schlechter (1929: 31), and Zootrophion dayanum Luer (1982: 82). Flowering of this species occurs between October and November, in the beginning of the wet season.	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
B71587ABFFFF263CFF70D440FD49F83A.taxon	etymology	Etymology: — In honor of the Yánesha indigenous people, an ethnic group that inhabits the Pichis and Palcazú river basins in the Oxapampa-Asháninka-Yánesha Biosphere Reserve (BIOAY), who have a deep knowledge of the region’s flora and fauna (Santos 2004 a, 2004 b) and who, despite the various challenges during the time of colonization in the 20 th century, were able to keep alive their traditions, language and ancestral practices, reflecting Peru’s great cultural diversity today (Cornejo 2015).	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
B71587ABFFFF263CFF70D440FD49F83A.taxon	conservation	Conservation status: — Pleurothallis yanesha is known from only three localities, it has been estimated that its populations has less than 100 mature individuals in an area of approximately 2 km 2. Therefore, P. yanesha is assessed as Endangered (EN) based on IUCN criteria B 2 ab (i, ii, iii) (IUCN 2024). The new species is currently threatened by anthropogenic activities such as indiscriminate forest burning, livestock, agriculture, and the expansion of grazing. These practices have caused an irreversible reduction and possible disappearance of the small remnants of forest where this species lives.	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
B71587ABFFFF263CFF70D440FD49F83A.taxon	materials_examined	Additional material examined (paratypes): — PERU. Pasco: Oxapampa, Chontabamba, cerro Mirador - Oxapampa, 2000 m, 18 November 2009, L. Valenzuela & A. Peña 13880 (HOXA 046950!; USM!); ibid., Huancabamba, sector Oso Playa, camino hacia el campamento, 2478 m, 22 October 2009, L. Valenzuela, A. Monteagudo et al. 13849 (HOXA 046959!). Other record: — PERU. Pasco: Oxapampa, caserío de Cantarizú, km 37, Centro Huaytianum de Estudio y Conservación de la Orquídea, flowered in cultivation, cultivated by Abel Huayta, 19 January 2021, L. Ocupa s. n. (Lankester Composite Dissection Plate) (Figure 4).	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
B71587ABFFF42635FF70D189FC11FC77.taxon	materials_examined	Type: — PERU. Huánuco: Without locality data [collected with M. Regina, November 1998, cultivated by A. P. Sijm at Venhuizen, Holland] November 1998, A. P. Sijm 200425 (holotype MO 277305!) (Figures 1 – 2, 8).	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
B71587ABFFF42635FF70D189FC11FC77.taxon	description	Description: — Plant epiphytic, caespitose, up to 43 cm high. Ramicauls suberect, stout, terete, green to very dark olive color, up to 16 cm long; enclosed by 1 – 2 brown, chartaceous, warty, tubular sheaths, located at the base and in the middle of the ramicaul. Leaves erect to spreading, sessile, coriaceous, narrowly elliptical, acute, 13 – 16 × 4.0 – 5.0 cm, conduplicate at the base. Inflorescence arising from a 1.2 – 1.5 cm long spathe, at the base of the leaf, with multiflowered successive, erect to horizontal, loose, secund coflorescences, 1 – 2 developing at a time, simultaneously with up to 10 successive flowers, up to 30 cm long, including the pseudopeduncle 12 cm long. Floral bracts tubular, acute, 5 mm long; pedicels terete, 7.0 – 12.0 mm long. Ovary terete, sulcate, red-purple colored, up to 8 mm long. Flowers yellow spotted and mottled red, petals yellow, densely impregnated with red, lip bright yellow, suffused with red spots, more densely clustered in the center of the basal half, column greenish white, anther cap white with a greenish yellow spot, pollinia fulvous. Dorsal sepal concave, narrowly ovate, 3 - veined, acuminate, acute, 24.5 – 30.0 × 7.5 – 8.0 mm, apex progressively contracted into a linear, acute tail. Lateral sepals narrowly ovate, 3 - veined, adaxially carinate, acuminate, apex progressively contracted into a linear, acute tail, connate 8 – 10 mm, or totally connate into a concave, elliptic, long-acuminate synsepal, 21 – 28 × 9 – 10 mm. Petals facing forward, obovate, 3 - veined, acuminate, 10 – 12 × 6.0 – 6.5 mm, apex abruptly contracted a long, filiform, acute tail, 13 – 15 mm long, with small verrucae on the apical third to the base of the tail, total length 23 – 29 mm. Lip attached to the column, 3 - lobed, 3 - veined, 13 – 14 × 8 mm when expanded, without glenion; low, broadly ovate callus; lamina with two parallel keels originating in the center of the lateral lobes and disappearing over the lateral veins, in the middle of the mid-lobe; the surface of the lip and callus are covered by sinuous ridges, which are distributed along the longitudinal center of the lip, from the callus at the base of the lip to the mid-lobe, the ridges at the base are more scattered, but they cluster distally at the base of the mid-lobe, forming a papillose-spiculate apex; lateral lobes erect in natural position, semi-orbicular, ca. 6 × 4 mm; mid-lobe oblong, obtuse, ca. 6 × 3 mm. Column arcuate, claviform, ventrally complanate, with two small, rounded wings at apex, projecting toward the base, giving it a channeled appearance, minutely ciliate at the base, 9.0 mm long; foot of column very short. Anther subapical, anther cap cucullate, hirsute on top, 2 - celled, ca. 1.7 × 1.8 mm; stigma ventral, orbicular. Pollinia 2, narrowly obovoid, ventrally flattened, 0.9 mm long. Capsule not seen.	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
B71587ABFFF42635FF70D189FC11FC77.taxon	distribution	Distribution and ecology: — To date, the first natural population of Pleurothallis sijmii has been observed in a humid montane forest located in the Garganta de la Bella Durmiente sector, a limestone mountain range that extends from north to south through the Tingo María National Park, in the department of Huánuco, and located on the eastern branch of the Andes mountain range (Figure 5). In this ecosystem, P. sijmii grows as an epiphyte on tree branches, in sympatry with other orchids such as Andinia tingomariana A. G. Diaz & Mark Wilson in Díaz et al. (2018: 223), A. barba-caprina Ocupa & S. Vieira-Uribe in Ocupa-Horna et al. (2021: 298), Ida peruviana (Rolfe 1910: 160) A. Ryan & Oakeley (2003: 28), Masdevallia concinna Königer (1982: 101), and Sobralia crocea (Poeppig & Endlicher 1836: 55) Reichenbach (1853: 247). Pleurothallis sijmii has been recorded flowering in March, at the end of the wet season.	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
B71587ABFFF42635FF70D189FC11FC77.taxon	conservation	Conservation status: — The only wild population of Pleurothallis sijmii is located within the Tingo María National Park, in the department of Huánuco, central Peru (MINAM 2016). Although the species occurs within a Natural Protected Area, the habitat of this species may be affected by anthropogenic activities occurring in this area, such as deforestation, agricultural expansion, and illegal orchid collection. In addition, although we do not know the actual population status, our observations indicate that the species exhibits a limited geographic range, small population size, and highly specialized habitat needs, suggesting that it may be geographically rare. Therefore, according to IUCN criteria (IUCN 2024), the species could potentially be classified as Data Deficient (DD).	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
B71587ABFFF42635FF70D189FC11FC77.taxon	materials_examined	Additional material examined: — USA. Purchased from Bryon Rinke at Southwestern College, Kansas, via George Norris of Houston, Texas, of unknown origin, and flowered in cultivation in the Colorado College greenhouse M. Wilson PL 0788 (COCO!, flowers in spirits); purchased from Lisa Thoerle, of unknown origin, and flowered in cultivation in the Colorado College greenhouse M. Wilson PL 0531, PL 0764 (COCO!, flowers in spirits). Other record: — PERU. Huánuco: Leoncio Prado, Mariano Dámaso Beraún, Parque Nacional Tingo María, sector Garganta, 1580 m, 12 March 2017, L. Ocupa s. n. (LCDP voucher) (Figure 8).	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
B71587ABFFF42635FF70D189FC11FC77.taxon	discussion	Scanning electron microscopy: — SEM of the lip of Pleurothallis sijmii PL 0788 (Figure 11) revealed a tissue type not previously reported for Pleurothallis during examinations of the labella of species of subsections Macrophyllae-Fasciculatae or Acroniae, or subgenera Ancipitia or Talpinaria. The entire longitudinal center of the lip, from just behind the papillose apex to the callous at the base of the lip, consisted of sinuous ridges which were closely packed towards the apex but more loosely packed towards the base. The ridges appear to be composed of densely packed columnar epithelial cells, each of which is lightly covered in small crystals (Figure 11 C). Taxonomic discussion: — Luer (2004) assigned Pleurothallis sijmii to subgenus Elongatia based in part on similarity to P. macrophylla. However, we believe that P. sijmii and P. yanesha share much greater floral similarity with three other species than they do with P. macrophylla: Pleurothallis scabrata Lindl. (1859: 30), Pleurothallis humboldtiana Luer (1976: 120) and Effusiella werneri Luer & Thoerle in Luer (2011: 324). All five of these species, P. scabrata, P. humboldtiana, P. sijmii, P. yanesha, and Effusiella werneri (Table 1), possess a three-lobed lip where the basal lobes are raised almost vertically creating a restricted ‘ channel’ for the pollinator toward the base of the lip; and in all five, the exterior or abaxial surface of the petals is scabrous at the point the petals abruptly narrow into the caudae (Figure 7 B). While preliminary phylogenetic studies using ITS and matK (Wilson unpubd.) suggest that these five species might represent a separate clade of Pleurothallis from other members of subgenus Elongatia, these phylogenies do not exhibit strong nodal support, hence phylogenomic studies are currently underway. These studies will determine whether or not these five species belong within Pleurothallis subgenus Elongatia or whether a new subgenus should be created to accommodate them. We do not doubt, however, that the five species belong in genus Pleurothallis, not in either Effusiella (Luer 2011) or Stelis (J. M. H. Shaw 2014), hence, herein we transfer Effusiella werneri to Pleurothallis, as Pleurothallis deuteowerneri Mark Wilson & Ocupa (a previous attempt to do this, as Pleurothallis florianwerneri Karremans (Karremans 2015), created an invalid combination). Floral morphology and implications for pollination: — The flowers of Pleurothallis sijmii (Figure 9) and P. yanesha are essentially “ gullet ” flowers, a term used by van der Pijl (1972) to describe “ bilabiate ” flowers of family Labiatae where the size of the pollinator is restricted by the two lips. In P. sijmii and P. yanesha the size of the pollinator would be restricted vertically by the lip and the column / ventral anther and horizontally by the upturned basal lobes of the lip (Figures 8 – 10). We might predict, therefore, that the pollinator of these species, likely a dipteran or possibly a hymenopteran, would be much larger than for the majority of Pleurothallis species and that the pollinarium would be deposited on the upper surface of the thorax of the insect. Flowers such as these have evolved to lure the pollinator onto the lip and then into the “ gullet ” through a combination of visual, chemical and tactile cues. While we hypothesized that these flowers provide a nectar reward, liquid nectar has never been observed on the lip P. sijmii on plants in cultivation. Neither do the lips of either species (Figures 10 – 11) possess a glenion, the small, circular, apparently secretory structure at the base of the lip in Pleurothallis subsections Acroniae and Macrophyllae-Fasciculatae hypothesized to correctly position the pollinator below the column / anther for pollinarium acquisition or deposition. However, the lips of both P. sijmii and P. yanesha (Figure 10) do exhibit an unusual shiny, ridged tissue along the center of the lip, from just above the apex to the base. This tissue, examined by SEM in P. sijmii PL 0788, consisted of interconnected sinuous ridges, constructed of tightly packed columnar cells that were diffusely coated with tiny crystals (Figure 11). This tissue, observed in SEM images of the lip of P. sijmii and in photographs of the lip of P. yanesha, has not been reported previously in any Pleurothallis species. Neither, to our knowledge, has such tissue been reported on the lips of other Pleurothallidinae, though it is somewhat similar to that observed in Acianthera ochreata (Almeida et al. 2019). We hypothesize that this is a previously undescribed secretory tissue type in Pleurothallidinae, that the crystals are dried nectar, and that nectar probably accumulates in the cavities between the ridges, rather than accumulating as liquid on the surface of the lip. Studies are currently underway at Colorado College to identify and quantify sugar concentrations in nectar washed from the lips of P. sijmii and other Pleurothallis species using liquid chromatography-mass spectrometry (LC-MS). Another notable morphological feature of the flowers of Pleurothallis yanesha that may be involved in pollinator attraction in this species are the long caudae on the petals, much longer than those in P. sijmii (Figures 4 and 8). Such long caudae are unique in Pleurothallis, but do occur in other genera in Pleurothallidinae, for example the extreme sepaline tails of Dracula chimaera. The function of such caudae or sepaline tails is unknown: these floral extensions could produce volatile pollinator attractants via osmophores, their length magnifying their effect; or they might provide an enhanced visual target for the pollinator. The full extent of Pleurothallis diversity in Peru remains incompletely understood. To address this, further efforts — such as expanded field explorations and a thorough taxonomic revision — are essential to more accurately identify and comprehend the richness of this genus within the country.	en	Ocupa-Horna, Luis, Valenzuela, Luis, Ward, Raven, Wilson, Mark (2025): A new, spectacular, long-caudate species of Pleurothallis (Orchidaceae) from central Peru related to P. sijmii. Phytotaxa 720 (3): 193-208, DOI: 10.11646/phytotaxa.720.3.1, URL: https://doi.org/10.11646/phytotaxa.720.3.1
