Chamaecrista ustulata ( Irwin & Barneby 1978: 159 ) Mendes & Silva In Mendes et al. (2020: 179)

Mendes, Thainara Policarpo, Souza, Alessandro Oliveira De & Silva, Marcos José Da, 2021, Taxonomic review of Chamaecrista sect. Absus subsect. Absus ser. Paniculatae (Benth.) H. S. Irwin & Barneby (Leguminosae, Caesalpinioideae), Phytotaxa 495 (1), pp. 1-64 : 58

12. Chamaecrista ustulata ( Irwin & Barneby 1978: 159) Mendes & Silva In Mendes et al. (2020: 179) . ≡ Cassia orbiculata var. ustulata Irwin & Barneby (1978: 159) ≡ Chamaecrista orbiculata var. ustulata ( Irwin & Barneby 1978: 159) Irwin & Barneby (1982: 655) . Type — BRAZIL. Minas Gerais: in much burnt, open cerrado =t 30 km n. of Francisco Sa, ± 5 0 km n.-e. of Montes Claros, 16 August 1960, fl, B. Maguire, Mendes Magalhães & C.K. Maguire 49232 (holotype: NY00003868!). Fig. 35

Shrubs 30–45 cm tall, decumbent. Stems with bark conspicuously longitudinally fissured, dark brown. Branches cylindrical, pendent, adult branches with bark conspicuously longitudinally fissured, dark brown, young branches with bark discreetly longitudinally fissured, brown, viscous-setulose, including petiole, margin of leaflets, primary veins, axis of inflorescences, pedicel, external surface of bracts, bracteoles, buds, sepals and fruits. Stipules 2.8−3.3 mm long, linear-subulate, pubescent, margin entire, persistent. Leaves 5.0–8.6 long, regularly distributed along the branches, ascending; pulvinus 2.8–4.0 mm, discreetly dilated, not striated; petiole 2.9−6.0 cm long, cylindrical, sulcate above, pubescent; rachis 1.1–2.7 cm long, cylindrical, sulcate above; pulvinule 1.1–2.5 mm, striated; leaflets (1) 2 pairs, coriaceous; blades 3.2–4.3 × 2.9–4.2 cm, orbicular, margin entire, corneously incrassate, setose, surface abaxial and adaxial puberulous, base asymmetrically rounded, apex rounded, with mucron, dark green, opaque; venation with secondary veins 7–9 pairs, yellowish. Panicles 26–42 cm long, 5–8 secondary axis, terminal, with flowers laxly distributed, erect, exserted from the foliage. Bracts 1.8–2.2 × 0.4–1 mm, lanceolate, apex acute, margin entire, yellowish, persistent. Bracteoles 1.2–2.1 × 0.2–0.3 mm, lanceolate, apex acute, margins entire, yellowish, persistent. Buds 0.9–1.2 cm long, ovoid, green, apex obtuse. Flowers 3–4.4 cm long; pedicel 1.4–3 cm long, robust, cylindrical; sepals 1–1.2 × 0.5–0.6 cm oval-lanceolate, apex obtuse, yellowish green; petals 1.1–2 × 1.1–2.2 cm, obovate, with the adaxial petal like a standard, one of the inner petals coiled in the androecium; stamens 0.5–0.7 mm long; filaments 0,9– 1 mm long; anthers 4–6 mm, not mucronulate at apex; ovary 3–4 × 1–1.2 mm; styles 1.2–1.3 cm long, pubescent. Legume 3.4–4.2 × 0.5–0.8 cm, narrow-oblong green, pubescent. Seeds unknown.

Representative specimens examined: — BRAZIL. Minas Gerais: Barrocão, cerca de 2 km da cidade de Barrocão na BR-251, sentido Francisco de Sá , 16°25’51’’S, 43°17’47’’W, 730 m, 09 July 2016, (fl., fr.), T. P . Mendes J. A. Oliveira & R. C. Sodré 290, 291 ( UFG). 04 July 2016, (fl., fr.), T. P . Mendes, A. O. Souza & R. G. Matos 376 ( UFG), 377 ( UFG), 378 ( UFG).

Distribution and ecology: —Species registered only for Minas Gerais, particularly in the Serra do Espinhaço region, near the municipality of Barrocão (Fig. 36D). It inhabits rocky savannahs on oxisols with outcrops of rocks on hillsides or roadsides, between 730–1100 meters elevetion.

Conservation status: — Chamaecrista ustulata is being considered as “In Danger” (EN, criterion B1, subcriteria b i, ii, v), regarding its conservation, as it was collected in only one location and has small populations (up to 40 individuals) distributed in an area of extension of occurrence of 1155 m 2.

Flowering and fruiting: —It was collected with flower and fruit in July.

Etymology: —The specific epithet “ ustulata ” refers to the burnt or “scorched” color of the species stem.

Morphological relationship and characterization: — Chamaecrista ustulata was recognized by Barneby (1982) as a variety of Ch. orbiculata (= Ch. Orbiculata var. ustulata ). Mendes et al. (2020) based on the results of his phylogenetic study for Ch. ser. Paniculatae and supported by morphological and geographic evidence, raised Ch. orbiculata var. ustulata to the species category (= Ch. ustulata ). Cota et al. (2020) recognized Ch. ustulata as a synonym for Ch. orbiculata without commenting on anything precisely and with weak arguments. After permorized analysis of several collections, as well as collections and observations of the taxa now being discussed in their habitats, we realized that Ch. ustulata has a set of characters that differentiates it from Ch. orbiculata . For this reason, we maintain the same decision made by Mendes et al. (2020) in considering both taxa as distinct species.

Among the other species studied here, Ch. ustulata is more morphologically similar to Ch. cercidifolia by share setulose branches, including inflorescence axis, external face of the stipules, bracts, bracteoles, sepals and ovaries, and for having two pairs of orbicularis leaflets with inconspicuously prominent tertiary venation. However, they are differentiated mainly by the shrubby habit decumbent in the first and arboreal in the second, pulvinus with 2.8–4 cm long (vs. 4–6 cm long) opaque dark green leaflets with setulose margin (vs. green-bluish leaflets with glabrous margin), panicles 26–42 cm long (vs. 11.2–26.9 cm long) and non-mucronulate anthers (vs. mucronulate), and pubescent fruits (vs. setulose on the margin).