Type:— BRAZIL. Tocantins: Mateiros, região do Jalapão, estrada Mumbuca-Boa Esperança, vereda do Bebedouro, 7 December 2005, fl., G.H. Rua 672 (holotype: SP!; isotypes: CEN!, CEPEC!).

Differs from Stigmaphyllon paralias by its consistently cordate laminas, discoid glands at the apex of petioles, absence of reduced leaves associated to inflorescences, claws of anterior-lateral petals longer, posterior petal eglandular, stamens opposite posterior-lateral petals straight, styles straight and parallel, anterior style equaling the posterior ones in size, and larger samaras.

Subshrubs to shrubs, 0.5–2 m tall, young branches laterally compressed, older branches cylindrical, longitudinally striated, densely sericeous-tomentose to sericeous, hairs yellowish; stipules 1–1.5 × 0.8–1.2 mm, triangular, both sides sericeous, persistent to deciduous at age. Leaves opposite, plane, never reduced in inflorescences; petioles 0.7–1.0 cm, canaliculate, densely sericeous, hairs yellowish, 1 pair of glands at apex, 2.0–2.5 × 0.9–1.0 mm, discoid, sessile; laminas 4.3–11 × 3.3–10 cm, chartaceous to coriaceous, orbicular to cordate, adaxially dark green, abaxially light green when dry, base cordate to occasionally auriculate, margin entire, plane, apex rounded, both sides densely sericeous at young, sparsely sericeous to glabrous at age, venation brochidodromous, primary veins adaxially impressed, abaxially prominent, 6–9 pairs of secondary veins, impressed on both sides, reticulum conspicuous. Umbels 3–4-flowered, sessile to subsessile, inflorescence peduncle 0.5–1.0 mm long, never subtended by a pair of reduced leaves; bracts 2.5–3.1 × 1.8–2.0 mm, ovate, apex acuminate, adaxially glabrous, abaxially sericeous; floral peduncle absent or up to 1 mm long, sericeous; bracteoles 1.8–2.0 × 0.8–1.0 mm, ovate, apex acute, both sides sericeous. Flower diameter 2.5–3.4 × 2.8–3.6 cm; mature floral bud orange, 0.5–0.7 × 0.5–0.7 mm; pedicels 22–29 mm long, erect, sericeous; sepals 3.5–4.5 × 3.5–3.6 mm, ovate, apex rounded to acute, adaxially glabrous, abaxially sericeous, lateral sepals biglandular at base, anterior sepal eglandular; glands greenish to light yellow, 1.5–1.7 × 1.0– 1.2 mm, elliptic; petals yellow to light orange, margin erose; anterior-lateral petals limb 14–18 × 14–15 mm, orbicular, both sides glabrous, claw 4.0–4.5 × 0.8–1.0 mm, both sides glabrous; posterior-lateral petals limb 15–15.5 × 13–14 mm, orbicular to suborbicular, both sides glabrous, claw 4.0–4.5 × 1.3–1.5 mm, both sides glabrous; posterior petal limb 12–12.5 × 13– 14 mm, depressed ovate, eglandular, both sides glabrous, claws 3.5–4.0 × 2.0– 2.2 mm, both sides glabrous. Stamens 10, heteromorphic; filaments 1.5–3.5 × 0.2–0.6 mm, connate at base, those opposite the posterior-lateral petals straight; connectives glandular, glandular tissue slightly expanded in those opposite lateral petals and sepals, inconspicuous in those opposite posterior petals and sepals, glandular tissue of those opposite anterior-lateral sepals curved downwards; anthers 0.6–1.1 × 0.2–1.0 mm, glabrous, those opposite posterior petal and posterior-lateral sepals elocular. Ovary 1.4–1.5 × 1.4–1.6 mm, ovate, tomentose; styles 3.3–4.1 × 0.25–0.30 mm, posterior styles longer, flattened distally, straight, divergent, glabrous, apex bearing apical folioles; folioles 1.4–2.1 × 0.8–1.6 mm, that of anterior style twosided, umbrella-like, those of posterior styles one-sided; stigmas lateral, pointing towards the center of the flower. Samaras greenish to brown; dorsal wing reduced to a crest, 2.0– 2.2 mm long, densely sericeous when young, sparsely sericeous to glabrous in maturity; nut 8.1–10 × 8.2–11 mm, globose, rugose, densely tomentose at young, sparsely sericeous to glabrous at age; areole 6.0–6.5 × 5.0– 5.6 mm. Seeds 8.5–9.0 × 5.0–6.0 mm, smooth. Embryo 6.0– 8.1 mm long, horseshoe-shaped, ca. 1.5 times as long as wide, outer cotyledon 8.7 mm long, 3.4–3.6 mm wide, the distal portion folded over the inner cotyledon, inner cotyledon 4.0– 4.4 mm long, 2.6–4.8 mm wide, straight.

Additional specimens examined (paratypes):— BRAZIL. Bahia: Formosa do Rio Preto, Fazenda Estrondo, 11°06’36’’S, 45°27’56’’W, 11 November 1997, fl., Alvarenga et al. 1053 (IBGE, MICH, SP). Goiás: Posse, 6 km de Posse, 23 November 1996, fl., Pereira & Alvarenga 3276 (IBGE, MICH, RB, SP); loc. cit., Road BR-020, 10 km S of Posse, 8 October 1976, fl., Hatschbach 39058 (CEPEC, HEPH, MBM, MICH). Piauí: Ribeiro Gonçalves, Estação Ecológica de Uruçuí-Una, caminho para Riacho do Prata, 8 December 1980, fl., Castro s.n. (TEPB 1370). Tocantins: Mateiros, Parque Estadual do Jalapão, brejo do Bebedouro, 7 December 2005, fl., Rezende 1041 (CEN); loc. cit., estrada entre Ponte Alta do Tocantins e Mateiros, 12 November 2011, fl., Faria Jr. 2154 (SP); loc. cit., estrada da Ponte Alta para Mateiros, 16. November 1998, fl., Farias 163 (HUEFS, UB); loc. cit., ca. 33 km de Mateiros, 10˚35’37”S, 46˚12’55”W, 626 m, 11 November 2009, fl. fr., Melo 7226 (HUEFS); loc. cit., próximo a Serra do Espírito Santo, 10°36’02’’S 46°36’50’’W, 490–760 m, fl. fr., Amorim et al. 9223 (CEPEC, RB); loc. cit., Estrada Rio Nova para Mateiros, 469 m, 9 October 2001, fl., Soares e Silva et al. 986 (UB).

Distribution, habitat and phenology:— Stigmaphyllon occidentale is known only from Brazilian sandy savannas and veredas, within the Jalapão Corridor region along the borders of states of Bahia, Goiás, Piauí and Tocantins (Fig. 6). Flowering from July to March and fruiting from December to March.

Conservation status: Stigmaphyllon occidentale is represented by few records restricted to the Jalapão region in state of Bahia, Piauí and Tocantins, and to the municipality of Posse in state of Goiás. Its extent of occurrence comprises 33,000 km ² within one of the major protected areas of Cerrado in Central Brazil, the Jalapão Region Ecological Corridor (ICMBIO 2013). Nonetheless, due to several threats imposed by farming, logging and mining activities, combined with its extent of occurrence, S. occidentale can be regarded as Vulnerable species (criteria B1a and B1b).

Etymology: The epithet refers to being the most continental species of S. paralias complex.

Discussion: Stigmaphyllon occidentale is part of the S. paralias complex, comprising four species with its diversity center in Eastern Brazil: S. bannisterioides (Fig. 2), S. harleyi Anderson (1981: 1) (Fig. 3), S. occidentale (Fig. 1), and S. paralias (Fig. 4). Leaf morphology greatly varies within this species complex, but consistently cordate leaves are exclusive to S. harleyi and S. occidentale. However, they can be readily differentiated by indumentum type, leaf, reproductive morphology, and habitat, with S. occidentale being endemic to savannas of Central Brazil and S. harleyi endemic to rocky fields in Chapada Diamantina, Bahia state. Stigmaphyllon bannisterioides is restricted to the coastal vegetation associated to the Amazon Forest, restingas from Northern Brazil to the Antilles and Mexico.

Some populations of S. paralias from Northeastern Brazil might present the first pair of leaves deeply cordate, resembling those from S. harleyi and S. occidentale. Nevertheless, in all populations of S. paralias observed in the field, this character is not retained in adult plants. After the development of branches, newly expanded leaves might vary in shape from oblong to widely elliptic, wide ovate or orbicular. A list of diagnostic characters to differentiate the species from the S. paralias complex is presented on Table 1.