Oreocharis odontopetala is most similar to O. elegantissima, having a similar shape of leaf blade, lanceolate sepals and bracts, stellate ring-like disc, pistil and fruits. Oreocharis odontopetala differs from O. elegantissima by its adaxially bullate leaf blade (vs. not bullate), with abaxially reticulate veinlets conspicuous (vs. veinlets inconspicuous); peduncles brown-purple (vs. green); adaxial corolla lobes triangular (vs. oblong) and abaxial corolla lobe margins with 4–10 long teeth (vs. margin nearly entire); style glabrous (vs. glandular pubescent) and stamens shorter (adaxial 0.5–1.4 vs. 2.0–2.6 cm, abaxial 0.8–1.8 vs. 2.3–2.7 cm) with confluent thecae at apex (vs. not confluent).

Figure 1. 

Oreocharis odontopetala. A habit; B flower; C opened corolla, showing lip lobes and stamens; D abaxial stamens (dorsal view); E cohering pair of anthers (anterior view); F adaxial stamens (dorsal view); G calyx, pistil and stigma; H bracts (ventral and dorsal view); I sepals (the two on the right showing ventral view and the three on the left showing dorsal view); J adaxial leaf surface; K abaxial leaf surface. Drawn by Ms Yun-Xiao Liu based on the holotype (WYQ-2018-112).

Figure 2. 

Morphological comparison of (A) Oreocharis odontopetala and (B) O. elegantissima. -1 habitat and habit. -2 adaxial leaf surface. -3 abaxial leaf surface. -4 opened corolla, showering lip lobes and stamens with anthers cohering in pairs. -5 anthers. -6 thecae, showing confluence at apex (white arrowhead), or no confluence (black arrowhead). -7 immature pistil and disc, showing glandular pubescence (B) or absence (A).

CHINA. Guizhou Province: Panzhou City, Wumeng Town, Wumeng grassland, growing on limestone rocks in hills, 26°4.33'N, 104°37.34'E, alt. 2100 m, 14 August 2018, Ying-Qiang Wang, WYQ-2018-112 (holotype: SN!; isotypes: SN!).

Perennial herbs, rosette forming. Rhizomes straight, terete, 0.8–2.1 cm long, ca. 0.8–1.1 cm in diameter. Leaves 8–18, basal; leaf blade papyraceous, usually ovate, rarely narrowly ovate and broadly ovate, 2.4–6.4(–7.2) × 1.3–3.5(–4.0) cm, apex acute, base rounded to shallowly cordate, margin crenate-serrate, adaxially green, bullate, white pubescent except veins, abaxially pale green, rust-brown sericeous along midrib and lateral veins, white pubescent along veinlets; lateral veins 4–7 pairs per side, adaxially inconspicuous and slightly concave, abaxially prominent, reticulate veinlets conspicuous; petiole 0.4–5.4(–7.0) cm, outer leaves with long petiole, densely rust-brown sericeous. Cymes 1–6, axillary, 1–2-branched, 1–6(–11)-flowered, each plant bearing 1–18(–22) flowers; peduncle 5.0–15.3(–19.3) cm long, 0.7–1.5(–2.1) mm in diameter, brown-purple, brown villous; bracts 2, opposite, green, lanceolate, (2.5–)3.3–8.0 × 1.0–2.7 mm, outside densely brown villous, inside glabrous, apex acute, margin entire. Pedicel 1.7–3.5 cm long, ca. 0.6–0.9(–1.2) mm in diameter, brown-purple, densely white glandular pubescent. Calyx 5-parted to near base, segments lobes equal, lanceolate to narrowly lanceolate, 4.2–7.3 × 1.4–1.8 mm, outside brown villous, inside glabrous, apex acute, margin entire. Corolla purple-red to purple, outside densely white glandular pubescent and sparsely villous, inside densely white glandular pubescent, 2.2–4.8 cm long; tube narrowly campanulate, gibbous abaxially, inside yellow and purple-red spotted, 1.4–2.9 cm long, 0.7–1.2 cm in diameter at middle; limb 5-lobed, zygomorphic, distinctly 2-lipped, adaxial lip 4.8–8.2 mm, nearly erect, 2-lobed to nearly middle, lobes triangular, apex acute, 2.0–4.1 × 2.0–3.8 mm, abaxial lip (0.8–)1.1–1.9 cm, 3-lobed to middle, lobes elliptic to ovate, margin with 4–10 long teeth, central lobe 5.6–9.8 × 3.2–7.6 mm, lateral lobes 4.0–8.6 × 3.1–6.3 mm. Stamens 4, coherent in pairs, included, adaxial stamens 0.5–1.4 cm, adnate to 4.5–8.3 mm above corolla base, abaxial stamens 0.8–1.8 cm, adnate to 3.5–7.0 mm above corolla base; filaments linear, slender, white glandular pubescent; anthers reniform, basifixed, glabrous, 1.9–3.1 × 1.8–3.0 mm, thecae 2, parallel, confluent at apex; staminode 1, 1.1–1.8 mm long, adnate to 2.7–4.6 mm above corolla base. Disc stellate ring-like, yellow-green, 1.5–2.5 mm high. Pistil 0.7–1.2 cm long at flower opening and 1.5–2.5 cm long at maturity, glabrous; ovary linear, 0.4–0.9 cm long at flower opening and 1.1–1.9 cm long at maturity, 0.9–1.1 mm in diameter, 1-loculed, placentas 2, parietal, projecting inwards, 2-cleft; style 1.8–2.7 mm at flower opening and 3.3–5.4 mm long at maturity; stigma 2, equal, 2-lipped, undivided, lingulate, apex obtuse, 0.6–0.9 mm long at flower opening and 1.4–1.6 mm at maturity. Capsule linear, straight, glabrous, ca. 37.2×1.7 mm, dehiscing septicidally by two valves at maturity.

Oreocharis odontopetala is only known from the type locality on Wumeng grassland, Wumeng Town, Panzhou City, Guizhou Province, China, 26°4.33'–26°8.62'N, 104°37.34'–104°36.35'E, alt. ca. 2100–2400 m.

The plants grow on limestone rocks of a hillside forest. Flowering in early August to late September, fruit ripe during early-September to October.

Based on our field investigations, the new species is currently only known from the type locality Wumeng grassland. Only ca. 300 mature individuals were present and the extent of occurrence is estimated to be ca. 5000 m². The location is not in a protected area and is accessible to casual hikers. According to the guidelines for using the IUCN Red List Categories and Criteria (IUCN 2017), the species is categorised as Endangered [EN B1abc(iv); C2a(i,ii)] due to its rarity and the threat of disturbance.

The species is named after its abaxial strongly toothed corolla lobes.

Chǐ Bàn Cū Tǒng Jǜ Tái (Chinese pronunciation); 齿瓣粗筒苣苔 (Chinese name).

(Fig. 3). The leaf epidermal cells of Oreocharis odontopetala on both adaxial and abaxial sides were irregular, with smooth cuticular membranes and sinuate anticlinal walls (Fig. 3A1–4). The epidermal trichomes on both adaxial and abaxial leaf blades were multicellular, with rugulate membranes (Fig. 3A2). The stomata apparata were only found on the abaxial epidermis and were assigned to the anisocytic type, with rugulate membranes, stomatal length 34.8 ± 3.4 (29.3–43.6) μm, stomatal width 26.9 ± 2.8 (21.7–31.7) μm (Fig. 3A4). The outer stomatal rims were striate (Fig. 3A4). The epidermal cells of the style were quadrilateral or polygonal, with striate cuticular membranes and many granular derivatives (Fig. 3A5).

Figure 3. 

Comparative morphology (LM & SEM) of leaf epidermal surface and epidermal cells of style between (A) Oreocharis odontopetala and (B) O. elegantissima. -1 adaxial leaf epidermal cells (LM). -2 adaxial leaf epidermal trichome and its cuticular membrane (SEM). -3 abaxial leaf epidermal cells (LM). -4 abaxial leaf cuticular membrane and stomata (SEM). -5 style epidermal cell shape and ornamentation (SEM).

It is worth noting that Oreocharis odontopetala shares the narrowly campanulate, abaxial gibbose corolla tube, anthers coherent in pairs at apex, as well as similar ovary structure with all other species of the former Briggsia. It is most similar to O. elegantissima, but is distinct from its congeners by its adaxially bullate leaf blade, abaxially conspicuous reticulate veinlets, brown-purple peduncles, triangular adaxial corolla lobes and abaxial corolla lobe margins bearing 4–10 long teeth, glabrous style and shorter stamens with confluent thecae at the apex, as well as the leaf epidermal characters. The detailed morphological comparison between O. odontopetala and O. elegantissima is provided in Tables 1, 2.

Furthermore, the characteristic, abaxial corolla lobe margins with 4–10 long teeth, is easily distinguished from other species of the enlarged Oreocharis. The bullate leaf is quite rare in the enlarged Oreocharis and only occurs in the new species and other few species such as O. bullata, O. curvituba, O. glandulosa, O. primuliflora, O. magnidens (and to a lesser degree O. × heterandra), but it has a very different corolla, style and stamen amongst these species (Li and Wang 2004; Wei et al. 2016). The stellate ring-like disc is also rare in the enlarged Oreocharis and only found in the new species, O. elegantissima and O. duyunensis (Guo et al. 2018). Therefore, this new species has a unique morphology amongst the species of the extended Oreocharis.