Chamaecrista trichothyrsus ( Harms 1924: 125 ) 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 : 55-58

11. Chamaecrista trichothyrsus ( Harms 1924: 125) Mendes & Silva In Mendes et al. (2020: 179) , ≡ Cassia trichothyrsus Harms (1924: 125) ≡ Cassia orbiculata var. trichothyrsus ( Harms 1924: 125) Irwin & Barneby (1978: 159) . ≡ Chamaecrista orbiculata var. trichortyrsus Irwin & Barneby 1982: 655 . Type: — BRAZIL: Goiás: Haut de la Serra Dourada, 1894/95, Glaziou 20971 (lectotype designated by Irwin & Barneby [1978: 159] K000555583!; isolectotypes: C 10011999!, G00371009!). Fig. 34

Dwarf shrubs 30–60 cm tall, with decumbent branches, or small trees 1.8 m tall, erect. Stems with bark conspicuously longitudinally fissured, dark brown or greyish. Branches cylindrical, erect, adult branches with bark conspicuously longitudinally fissured, dark brown or greyish, young branches with bark discreetly longitudinally fissured, light brown, viscous, hispid-setose, golden, including, petiole, margin of leaflets, rachis, axis of inflorescences, pedicel, external surface of stipules, bracts, and bracteoles, buds, sepals, ovary and fruits. Stipules 1.8−3.8 mm, long, linear-subulate, persistent. Leaves 6.2–10.8 cm long, distributed along the branches or in their terminations, ascending; pulvinus 1.2–3 mm long, discreetly dilated, not striated; petiole 4.2−7.8 cm long, cylindrical, sulcate above; rachis 2–3.8 cm long, cylindrical, sulcate above; pulvinule 1.4–2.3 mm long; leaflets (1) 2 pares, coriaceous; blades 3–7.1 × 2.3–7.1 cm, ovate, margin entire, corneously incrassate, setose, surface abaxial and adaxial glabrous, base asymmetrically rounded, apex obtuse, with mucron, dark green, opaque; venation with secondary veins 7–9 pairs, yellowish. Panicles 17–28 cm long, com 4–6 secondary axis, terminal, with congest flowers, erect, exserted from the foliage. Bracts 0.8–2.2 × 0.4–0.8 mm, lanceolate, apex acute, margin entire, yellowish, persistent. Bracteoles 1–1.2 × 0.4–0.6 mm, lanceolate, apex acute, margins entire, yellowish, persistent. Buds 0.8–1.2 cm long, ovoid, green, apex obtuse. Flowers 4–5.4 cm long; pedicel 1.8–3.5 cm long, robust, cylindrical; sepals 1.2–1.4 × 0.4–0.5 cm, oval-lanceolate, apex obtuse, yellowish green; petals 1.1–2.9 × 1.1–2.5 cm, obovate, with the adaxial petal like a standard, one of the inner petals coiled in the androecium; stamens 5–6 mm long; filaments 1 mm long; anthers 4–5 mm long, not mucronulate at apex; ovary 3–4 × 1–1.2 mm; styles 1.2–1.3 cm long, pubescent. Legume 3.2–4.7 × 0.5–0.8 cm, oblong, green to vinaceous, pubescent. Seeds 6–7 × 3–3.8 mm, ovoid, light brown, smooth, glossy.

Representative specimens examined: — BRAZIL. Goiás: Mossâmedes, Cerca de 20 km de Goiás, 19 January1966, (fr.), H . S . Irwin et al.11797 ( UB); ib., Serra Dourada, divisa dos municípios de Mossâmedes ao Sul e Goiás Norte, Área da UFG , 01 June 1969, (fl.), J . A . Rizzo 4267 ( UFG, UEC); ib., Cerca de 15 km de Goiás, 10 May 1973, (fl.), W . R . Anderson 9998 ( UB); ib., entrada Mossâmedes-REBIO da Serra Dourada, 16°04’54’’S, 50°11’14’’W, 922 m, 20 July 2007, (fl., fr.), R . C . Forzza et al 4539 ( ESA); imediações da cancela que dá acesso a sede do Parque, 16º04’37,7’’S, 50º11’24’’W, 998 m, 30 April 2011, (fl.), M . J . Silva 3618, 3619 ( UFG); 2 July 2011, (fl., fr.), M . J . Silva 3713 ( UFG); 26 August 2011, (fr.), M . M . Dantas 1 ( UFG); arredores da Pedra Goiana, 16º04’51.8’’S, 50º11’28.7’’W, 982 m, 30 April 2011, (fl.), M . J . Silva 3632 ( UFG); após o Areal entre fendas de rochas, 27 May 2011, (fl., fr.), M . J . Silva 3672 ( UFG), 3674 ( UFG); ib., Parque Estadual da Serra Dourada , Próximo ao alojamento dos pesquisadores, 16°4’29’’S, 50°11’4’’W, 1002 m, 18 June 2016, (fl., fr.), T . P . Mendes & J . A Oliveira 169 ( UFG), 170 ( UFG), 171 ( UFG), 172 ( UFG), 173 ( UFG), 174 ( UFG), 175 ( UFG), 176 ( UFG), 177 ( UFG), 178 ( UFG), 179 ( UFG), 180 ( UFG) .

Distribution and ecology: —Species microendemic from the Serra Dourada State Park in the state of Goiás (Fig. 36C). It inhabits in the cerrados rupestres and less often in the cerrados típicos, growing on soils with outcrops of sandstones or limestones, sand-stony between altitudes of 800 and 1000 meters.

Flowering and fruiting: —It was collected with flowers and fruits between June and July.

Etymology: —The specific epithet “ trichothyrsus ” results from the union of the words “ trichos ” which means trichomes and “ thyrsus ” which means tirso and the species was designated by the density of golden trichomes in their inflorescence which by the way is a panicle and not a tirso.

Conservation status: —Due to its small area of occurrence (1,000 km 2), and because it is micro-endemic to Serra Dourada, a Conservation Unit of the Goiás state, this species is being considered as Vulnerable (VU, criterion B1, subcriteria b i, ii, v) even though it inhabits a region protected by law.

Morphological relationships and characterization: — Chamaecrista trichothyrsus was described by Harms (1924) as Cassia trichothyrsus . Irwin & Barneby (1978) recognized it as a variety of Cassia orbiculata (= C. orbiculata var. trichortyrsus ), however in 1982 they transferred it to the genus Chamaecrista and kept it as a variety of Ch. orbiculata (= Ch. orbiculata var. trichotyrsus ). Mendes et al. (2020) carried out a phylogenetic study for Ch. ser. Paniculatae, which revealed that Ch. orbiculata var. trichothyrsus emerged in a distinct clade (clade 1a) of Ch. orbiculata var. orbiculata (clade 1b) with 1PP, 83% Boostrap and 99% Jackknife. In this same work, Mendes et al. (2020) presented a list of species for the series, where Ch. orbiculata var. trichothyrsus was elevated to a species category based on the results of his phylogenetic studies and on morphological and geographic evidence. Cota et al. (2020) proposed the synonymization of Ch. trichothyrsus under Ch. orbiculata , stating that the characters used in the study Mendes et al. (2020) were not enough to keep such taxa as distinct. After studies of collections from different locations, observations in the field, consultation of herbaria collections, we realized that Ch. orbiculata var. trichothyrsus has very different characters from those of Ch. orbiculata in addition to a specific geographic distribution (Serra Dourada State Park, Goiás) and allopatric that of Ch. orbiculata . For this reason, we have chosen to present Ch. trichothyrsus as a distinct species from Ch. Orbiculata .

Chamaecrista trichothyrsus shares with Ch. orbiculata the stem and adult branches with longitudinally fissured bark, leaflets with a horny and thickened margin and prominent tertiary veins, in addition to large flowers (4.0– 5.4 cm long), with robust pedicel, young villous branches, lanceolate stipules. However, both species can be differentiated by the characters listed in table 2.