Rinorea bicornuta Hekking

Hoyos-Gómez, Saúl E., Ballard Jr., Harvey E., Callejas Posada, Ricardo & Wahlert, Gregory A., 2025, Taxonomic clarifications, a new combination, and three new species of Neotropical Rinorea (Violaceae), PhytoKeys 256, pp. 151-174 : 151-174

9. Rinorea bicornuta Hekking . Phytologia 43: 474. 1979.

Type.

Brazil • Amazonas: Tocantins, Solimões , 1927, W. A. Ducke 21353 (holotype: RB [barcode RB 00560922 ]!; isotype: RB [barcode RB 00544454 ]!) .

Description.

Tree 5–12 m tall, branchlets densely strigose with ferruginous erect trichomes 0.2–0.3 mm long, lenticels 0.5–1 mm long. Leaves alternate, petiolate, petioles 6–9 mm long, pilose with golden appressed trichomes 0.3–0.6 mm long, glabrescent; stipules deciduous, free, triangular, 3–4 × 1–1.7 mm, veined, costa pilose, margin ciliate, apex acuminate, mucronulate; lamina elliptic, 10–25 × 5–12 cm, foliaceous, glabrous on both sides, costa sparsely pilose on both sides with golden appressed trichomes 0.1–0.3 mm long, with 8 to 11 pairs of major secondary vein, tertiary venation brochidodromous, base symmetrical, cuneate; margin subentire to subcrenate, apex acuminate, acumen 0.5–1 cm long, mucronulate, domatia absent. Inflorescence axillary and terminal, thyrsoid, solitary or in 2 to 3 fascicles, 7–15 cm long, rachis green when fresh, brown when dry, cymules with 1 to 5 flowers; common peduncle 2.5–5 mm long, pubescent with dispersed pilose golden trichomes 0.1–0.2 mm long; pedicels 2–4 mm long, articulated near the base, pubescent with pilose golden trichomes 0.1–0.2 mm long; bracts deciduous, lanceolate, 1–1.5 × 1–1.5 mm, costa pubescent with golden pilose trichomes 0.1–0.2 mm long, margin ciliate, mucronulate; bracteoles deciduous, ovate, 0.8–1.1 × 0.4–0.6 mm, subopposite, costa pubescent with golden pilose trichomes 0.1–0.2 mm long, margin ciliate, apex acuminate, mucronulate. Flowers subzygomorphic, 3.5–4 × 3.5–4 mm, flower buds conical; sepals ovate, 1.5–2 × 0.9–1.1 mm, pubescent near the base and along the costa with pilose golden trichomes 0.1–0.2 mm long, margin ciliate, apex subobtuse, mucronate, with 1–3 longitudinal veins; petals cream-colored, ovate, 3–4 × 0.8–1.5 mm, pubescent along the costa with dispersed pilose golden trichomes 0.1–0.2 mm long, margin sparsely ciliate, apex obtuse, cream when fresh, brown when dry; stamens 2.5–3 × 1.0– 1.2 mm, filaments and dorsal glands adnate to form a staminal tube 0.2 mm tall, carnose, glabrous, anthers 0.8–1 × 0.4–0.5 mm, subsessile, ovoid, with two apical cusps 0.3–0.5 × 0.1–0.2 mm; connective ca. 0.75 × ca. 0.25 mm, pubescent with dispersed pilose trichomes 0.1–0.2 mm long, dorsal anther connective scale lanceolate, 2–2.5 × 0.7–0.9 mm, scarious, margin entire, apex acuminate, brown when dry; ovary 0.8–1 mm, ovate, pubescent apically with pilose golden trichomes 0.2–0.3 mm long; style 2–2.5 mm long, erect, glabrous, stigma apiculate. Fruit an asymmetrical capsule dehiscent along three sutures, ellipsoid, 5–12 mm × 4–8 mm, pubescent with dimorphic golden trichomes, smaller trichomes 0.1 mm long, erect, larger trichomes 0.2–0.4 mm long, appressed; valves unequal, large valve 10–12 × 5–6 mm, smaller valves 6–7 × 4–5 mm, with persistent floral parts at the base. Seeds one per valve, ovoid, 4–5 mm diam., glabrous, shiny brown without maculae, with a conspicuous lateral hilum (Fig. 9 ).

Distribution and habitat.

Rinorea bicornuta is an endemic species near the border region of Colombia and Brazil, an area corresponding to the Imerí biogeographical province (sensu Morrone 2014; Fig. 8 ). It occurs in primary lowland wet forests between 50 and 200 m elevation.

Phenology.

The species was recorded in flower in February and November and in fruit in February.

Notes.

Rinorea bicornuta was described by Hekking (1979) from a single flowering specimen. Over the course of revising the genus from Colombia, a second fruiting herbarium specimen from Vaupés Department was observed and allowed us to provide and updated description here.

Additional specimens examined.

Colombia. Vaupés: • Taraira, Estación Biológica Mosiro Itajura (Caparú) , 01°04'21.8"S, 69°31'2.9"W, 200 m, 20 Feb 2004 (fl, fr), L. Clavijo 404 ( COAH, COL, HUA, UBDC) .

Figures

Figure 8. Distribution of Rinorea bicornuta (stars) and R. deflexa (triangles).

Figure 9. Rinorea bicornuta Hekking A fruit with asymmetrical valves B detail of pubescence on fruit surface C seed, glabrous without maculae (A – C: L. Clavijo 404 [HUA]).