Platystele peruviana sp nov. (Orchidaceae), the smallest orchid from Peru Author Rizo Patrón, Federico L. 0000-0002-2261-1078 Centro Neotropical de Entrenamiento en Humedales - Perú, Carretera San Alberto km 5.5, Oxapampa 15302, Perú. & feluse 30 @ gmail. com; https: // orcid. org / 0000 - 0002 - 2261 - 1078 feluse30@gmail.com text Phytotaxa 2022 2022-09-14 564 1 113 120 journal article 10.11646/phytotaxa.564.1.9 1179-3163 7077917 Platystele peruviana Rizo-Patron , sp. nov . ( Figures 1–3 ) Type: — PERU . Oxapampa : Gramazú , 1934 m , 01 September 2020 , FRV 52 ( holotype HOXA!) . Platystele peruviana is similar to P. psix Luer & Hirtz , but differs from the lateral parallel falcate sepals ( vs. oblique not falcate), ovate elliptic lip ( vs. ovate lanceolate), and a large circular glenion ( vs. medium semi square glenion). Description:— Plant epiphyte, caespitose, erect up to 14 mm tall: Roots basal, slender, up to 1 mm diameter, with compressions every 2 to 3 mm ; Ramicauls slender, suberect, 1 mm long, covered by 2 thin tubular sheaths; Leaves thickly coriaceous, conduplicate, elliptic, erect, apex subacute, tridenticulate, 8–9 × 3.5–4 mm , abscission layer visible, short conduplicate petiole, 2 mm long; Inflorescence an erect raceme, with successive flowers, up to 12 mm long, peduncle 9 mm long; Flowers flat, sepals and petals pale yellow to transparent towards the margins and darker towards the midvein, covered with glandular hairs, Dorsal sepal lanceolate, apex acute, 3.0 × 0.75 mm ; Lateral sepals more or less parallel, subfalcate, 3 mm × 1 mm , connated a quarter of the length of the sepals; Petals, lanceolate, with the upper margin curved towards the top in the central third, the lower margin strait, 2 × 0.5 mm ; Lip red with an orange tip, with whitish-yellow glandular hairs, ovate - elliptic, with the apex acute, 1.0 × 0.75 mm , with a circular glenion in the base; Column pale yellow, short, 0.3 mm tall; 0.4 mm long, 0.75 mm wide; Anther with more intense yellow in comparison to the column, 0.25 × 0.25 mm ; Pollinia yellow, ovoid from the side. Distribution and ecology :— Platystele peruviana is found only in Oxapampa, Pasco , Peru ( Figure 1 ) and could be considered, at this moment, the smallest orchid in Peru . Oxapampa is part of the Oxapampa Ashaninka Yanesha Biosphere Reserve – BIOAY. Etymology: —The specific epithet has been chosen to honor Peru , the country where the type specimen of this species was found. Taxonomic Discussion: — Platystele peruviana is similar to Platystele psix Luer & Hirtz with the exception of the lateral sepals, which are more parallel than oblique and with a subfalcate shape ( Figures 2A and 3A ). Also, the lip in P. psix is ovate-lanceolate with an acute apex, while the lip of P. peruviana is ovate-obtuse, resembling that of P. napintzae Luer & Hirtz ( Luer 1992: 114 ) ( Figures 2E and 3C ). The glenion is circular and approximately half as wide as the lip base, which is semi square in P. psix ( Figures. 2E , 3C 3D , 4A, 4C and Table 1 ). A comparison between P. peruviana , P. psix , P. lancilabris (Schlechter 1923: 102) , P. oxyglossa ( Garay 1974: 120 ) and P. pisifera (Luer 1977: 232) , which can be found in nearby locations, is presented in Table 1 . The descriptions of the different Platystele species mention that roots are coarse, slender and fleshy ( Luer 1990 , 1991 , 1992 , Jost & Iturralde 2017 ). No description mentions if any species have little constant compressions along the roots as are shown in Figure 2F, 2G and 4D . Connation of lateral sepals is also different from other species. This is shown in Figure. 4B and Table 1 . FIGURE 1 . Map of the distribution of the different Platystele species in Peru. FIGURE 2 . Platystele peruviana Rizo Patrón. Drawn from the plant that served as Type. Illustration by F. Rizo Patrón. FIGURE 3 . Platystele peruviana . A. Frontal view and natural color. B. Lateral view. C. Front detail of the column and the lip. D. Lateral detail of the column and the lip. by F. Rizo Patrón (FRV52, HOXA). In the treatment for Platystele ( Luer 1990 ) and its addenda ( Luer 1991 , 1992 ), nine Peruvian species are bigger than 5 cm from the base. Only Platystele psix has a plant bigger than 2 cm from the base, and P. peruviana is only 1.4 cm . from the base.