Chamaecrista cercidifolia ( Irwin & Barneby 1978: 160 ) Mendes & Silva In Mendes et al. (2020: 178)

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 : 19

2. Chamaecrista cercidifolia ( Irwin & Barneby 1978: 160) Mendes & Silva In Mendes et al. (2020: 178) ≡ Chamaecrista orbiculata var. cercidifolia ( Irwin & Barneby 1978: 160) Irwin & Barneby (1982: 655) ≡ Cassia orbiculata var. cercidifolia Irwin & Barneby (1978:160) . Type: — BRAZIL. Minas Gerais: In campis altis petrosis, Serra de Itambé, May 1818, (fl., fr.), Martius s.n. (holotype: M0217511!). Figs. 10 and 11

Small tree 0.7–1.5 m tall. Stems with bark longitudinally fissured, dark brown. Branches cylindrical, erect, adult branches conspicuously fissured, dark-brown, young branches discreetly fissured, light-brown, viscous-setulose, including rachis, axis of inflorescence, pedicel, external surface of stipules, bracts, and bracteoles, sepals, buds, ovary and margin of fruit. Stipules 4.2−50 mm long, lanceolate, persistent. Leaves 5.3–7.8 cm long, regularly distributed along the branches, plagiotropic; pulvinus 4–6 mm long, discreetly dilated, not striate; petiole 2.9−6.1 cm long cylindrical and not sulcate above, pubescent; rachis 2–2.3 cm long, cylindrical and not sulcate above; pulvinule 1.2– 2.9 mm long, visibly dilated; leaflets (1) 2 (3) pairs, coriaceous; blades 3.4–5.8 × 3.6–5.1 cm, orbicular, margin entire, plane, glabrous, surface abaxial glabrous and adaxial pubescent, base asymmetrically rounded, apex rounded, without mucron, bluish-green, opaque; venation brochidodromous, secondary veins 6–11 pairs, green in abaxial surface and yellow in adaxial surface. Panicles 11.2–26.9 cm long, with 1–8 secondary axis, not geminate, terminal, with flowers laxly distributed, erect, exserted from the foliage. Bracts 1.2–2 × 0.6–1 mm, lanceolate or triangular, apex obtuse or acute, margin entire, yellow, persistent. Bracteoles 1.1–1.6 × 0.1–0.2 mm, lanceolate, apex acute, margin entire, vinaceous, at apex of pedicel, persistent. Buds 0.9–1.4 cm long, ovoid, green, apex obtuse. Flowers 2.7–4.1 cm long; pedicel 1–1.8 cm long, robust, cylindrical; sepals 1.2–1.3 × 0.5–0.6 cm, elliptic or ovate, apex obtuse, light green; petals 1.8–2.5 × 1–2.2 cm, obovate, with the adaxial petal like a standard, one of the inner petals small (0.7–0.9 mm long), the other coiled in the androecium; stamens 0.6–1 cm long, filaments 1mm long; anthers 5–9 mm, mucronulate at apex. Ovary 3–5 × 1 mm; styles 1–1.3 cm long, pubescent. Legume 2.2–3.8 × 0.5–0.8 cm, narrow-oblong, green, margin setulose. Seeds 1 × 0.7 mm, ovoid, darkish, smooth, and glossy.

Representative specimens examined: — BRAZIL. Minas Gerais: Montes Claros, cerca de 30 km da cidade de Montes Claros na estrada para Juramento, 15 May 1977, (fl.), P. E . Gibbs, R . Abbott & J. B . Andrade 5134 ( SP); Senador Modestino Gonçalves , BR-367, cerca de 5km antes de entrar na BR 451 , km 515, 17°49’55’’S, 43°22’53’’W, 968 m, 09 July 2016, (fl., fr.), T. P . Mendes & J. A . Oliveira 276, 277, 278, 279, 280, 281, 282 ( UFG); ib., 08 August 2017, (fl., fr.), T. P . Mendes, A. O . Souza & R. G . Matos 387 ( UFG); Rio Pardo de Minas , 42°40’11.8”W, 15°35’02.5”S, 761 m, 31 July 1962, (fl., fr.), E . Amante s.n. ( SP); ib., Estrada Serranópolis-Rio Pardo , 15°58’54.0”S, 42°50’10.0”W, 881m, 13 May 1998, J. R . Pirani 4284 ( SPF, HUEFS) .

Distribution and ecology: —Species possibly endemic to the northern portion of the state of Minas Gerais (Fig. 17B), where it inhabits the transition between the cerrado rupestre and Caatinga (Fig. 1G) on oxisols with rocky outcrops, between 650–1000 meters elevation.

Flowering and fruiting: —Flowering and fruiting from May to July.

Etymology: the epithet “ cercidifolia ” refers to the similarity of the leaflets of this species with those of the genus Cercis L., also belonging to Leguminosae.

Conservation status: —Species is here classified as Critically Endangered (CR, criterion B1, subcriteria bi, iii, iv), for its small area of occurrence (1,030 km 2), for its populations with less than 30 mature individuals and for having been collected in only three locations, not protected by law.

Morphological relationships and characterization: — Chamacerista cercidifolia has been described as a variety of Ch. obiculata by Irwin & Barneby (1982). Mendes et al. (2020) recognized it as a distinct species based on a set of morphological characters and its molecular study. Cota et al. (2020), probably based on Irwin & Barneby’s decision, synonymized Ch. cercidifolia under Ch. orbiculata arguing that the characters listed by Mendes et al. (2020) to differentiate both taxa are insufficient and that both emerge in weakly supported clades. However, verifying the work of Mendes et al. (2020) we note that Ch. cercidifolia and Ch. orbiculata , besides emerging in different clades, which denotes an origin not common to both immediately, their clades are robustly supported (1 PP, 83% BS and 99% JK). In addition, the analysis of multiple herborized collections in addition to collections and observation of taxa now under discussion in nature, we could see that both have discontinuous morphological characters and geographic allopatric distribution, which is why we insistently opted to keep both as distinct species.

Chamaecrista cercidifolia can be recognized by the erect branches, plagiotropic leaves, setulose inflorescences, setose buds, mucronulate anthers and fruits with a setulose margin. It resembles Ch. orbiculata by the arboreal habit, stem with fissured bark. However, it has orthotrophic leaves with 2 pairs of leaflets with a non-thickened margin, fruits with a setulose margin, whereas Ch. orbiculata has ascending leaves, with 2–4 pairs of leaflets with a thickened margin, totally setulose fruits. Additionally, Ch. orbiculata occurs in states of Bahia, Goiás, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Pernambuco, Piauí and Tocantins and the Federal District, while Ch. cercidifolia is endemic to the northern portion of Minas Gerais, but not sympatric to Ch. orbiculata .