6. Piptadenia pteroclada Benth., Trans. Linn. Soc. London 30(3): 370. 1875. Figs. 2 i-k; 5f-i

Trees, 8–15 m tall, trunk with suberose wings, 2–4 mm tall; young branches angular, puberulous to sericeous-villose, aculeus straight, in a longitudinal series on the ribs of the branches. Stipules 5–6 mm long, narrowly triangular, caducous. Leaves bipinnate; petiole 1.4–3.6 cm long, angular; rachis 7–12 cm long, angular; petiolar nectary sessile, 3–5.1 × 2.5–3.2 mm, lentiform, obovate or elliptic, sometimes between the two last pinna pairs, sessile, discoid; pinna pairs 8–16; leaflets in 41–57 pairs per pinna, 4.7–9.6 × 1.1–2 mm, lanceolate, base asymmetrically truncate, apex acute, adaxial surface glabrous, abaxial surface sericeous-adpressed to sparsely sericeous-adpressed. Inflorescences spiciform, grouped, terminal; peduncle 0.4–1 cm long; rachis 9.5–12.5 cm long; bracts 0.6–0.8 mm long, ovate, persistent. Flowers subsessile, pentamerous, calyx campanulate, puberulent, tube 0.7–1 mm long, lobes 0.1–0.3 mm long; corolla infundibuliform, sparsely sericeous, whitish, tube 0.8–1 mm long, lobes 1.3–1.5 mm long; androecium tube 0.5–0.8 mm long, included, stamens 10, 3.3–4 mm long, pinkish white to reddish white, anthers with glands on the connective; nectary disc absent; gynoecium stipitate, stipe 1–1.4 mm long, ovary 0.7–1 mm long, sparsely sericeous, style 2.2–2.5 mm long, stigma punctiform. Fruit a legume, 7–12.3 × 1.7–2.1 cm, narrowly elliptic, base acute, apex obtuse to rounded, margins evident, surfaces glabrous with irregular veins; seeds 5–10.

Examined material: Alta Floresta, estrada vicinal 2ª Oeste, 09°53’25”S, 56°8’18”W, 28.IV.2023, fl., J. M. Fernandes 1951 (HERBAM); 27.VII.2023, fr., J. M. Fernandes 1972 (HERBAM). Carlinda, casa de sementes, 09°55’06”S, 55°45’17”W, fl., L. Rodrigues 784 (HERBAM). Vila Bela da SantÍssima Trindade, Fazenda Barranco Alto, 14°56’37”S, 60°00’41”W, 22.III.2014, fl., M. F. Simon et al. 2252 (Fotografias CEN 87263! and NY 2480114!) .

This species occurs in Brazil, Colombia, Ecuador, Peru, and Venezuela (GBIF 2023b; Ribeiro & Queiroz 2024). In Brazil, it had been recorded in the states of Amazonas and Pará in terra firme forests (Ribeiro & Queiroz 2024). In the state of Mato Grosso, it was found in the municipalities of Alta Floresta, Carlinda and Vila Bela da SantÍssima Trindade in seasonal semideciduous forest and vegetation on rocky outcrops (Fig. 4).

Piptadenia pteroclada is similar to P. gonoacantha (Martius 1837: 109) J.F. Macbride (1919: 17) because of the arboreal habit and stem with straight aculeus in a longitudinal series, but it differs by the presence of elliptical nectaries on the petiole and leaflets (7–12 × 1.4–2.4 mm) and larger inflorescences (12–22 cm long), while P. gonoacantha has annular or conical nectaries on the petiole and leaflets (4.5–7 × 0.8–1.2 mm) and smaller inflorescences (5.8–11 cm long) (Ribeiro & Queiroz 2024). Additionally, the suberose wings on the stem of P. pteroclada are up to 4 mm tall, while those of P. gonoacantha can be over 10 mm tall.

This work increases the number of Inga and Piptadenia species for Mato Gross and reports the first record of the genus Macrosamanea for the state, demonstrating the importance of field expeditions in Amazonia in Mato Gross, studying herbarium collections, and taxonomy as a science.