China. Guizhou Province, Panzhou, Dazhai village, west of Luotuo valley, limestone mountains, 1803 m a.s.l., herbaceous tier in mixed forest, 26°04'37.59"N, 104°51'47.40"E, 1 September 2020, Z. Li & M. Tang 2020-0901 (holotype JXAU! isotypes GZAC! JXAU!).

Figure 1. 

Holotype of Synotis panzhouensis (Panzhou, Guizhou, China, Z. Li & M. Tang 2020-0901 (JXAU)).

Synotis panzhouensis is similar to S. nayongensis but differs from the latter species by its larger involucral bracts (7–8 × 3–4 mm vs. 5–6 × 2–2.5 mm) and phyllaries (7–8 × 2–3 mm vs. 5–6 × 1–1.5 mm), higher number of phyllaries ((7) 8 vs. 5) and disk florets (8–11 vs. 4–5), different colour of phyllaries (green vs. white with green apex) and pappus (red-purple vs. white).

Figure 2. 

Synotis panzhouensis in the wild (Dazhai village, Panzhou, Guizhou, China). A habitat B general habit C portion of vegetative stem D leaf blades (left two: adaxial surface; right four: abaxial surface) E synflorescence F capitulum (top view) G capitulum (side view) H a disk floret with red-purple pappus. Scale bars: 5 mm (C); 10 cm (D); 4 mm (F); 1 cm (G, H).

Figure 3. 

Synotis nayongensis in the wild (Luzui village, Nayong, Guizhou,China). A habitat B habit C portion of vegetative stem D leaf blades from the adaxil view E synflorescence F portion of synflorescence (side view, note the white phyllaries with green apex, and also note the white pappus). Scale bars: 5 mm (C); 6 mm (F).

Perennial herbs, erect, rhizomatous. Rhizome thick, horizontal. Vegetative stem solitary, erect, 20–35 cm, densely white or ferruginous setulose. Flowering stem solitary, erect, scapiform, 30–60 cm tall, shortly branching, fulvous tomentose. Leaves rosulate at the base of fertile shoot; petioles 1–1.5 cm long, not winged, slightly expanded at base; blades oblanceolate or obovate, 10–18 × 2.5–5 cm, papyraceous, abaxially sparsely arachnoid, glabrescent or subglabrous, adaxially scattered setulose, pinnately veined, lateral veins 12–16, arcuate-ascending, base cuneate, margin shallowly sinuate-apiculate or repand-apiculate, apex subacute-acuminate. Stem leaves on reproductive shoots few, narrowly lanceolate, remote, much smaller. Capitula discoid, numerous, arranged in an attenuate narrowly paniculoid thyrse; pedicels 3–5 mm, fulvous tomentose, 1- or 2- bracteate; bracts below capitula linear, 5–10 mm long. Involucres narrowly campanulate, 7–8 × 3–4 mm, calyculate; bracts of calyculus 3–5, ovate-oblong or lanceolate, 1/4–1/3 as long as phyllaries; phyllaries (7) 8, narrowly oblong, 2–3 mm wide, herbaceous, green, margin narrowly scarious, glabrous, not veined, apically triangular, obtuse. Ray florets absent. Disk florets 8–11; corolla yellow, 8–10 mm, with tube 7–8 mm long, limb narrowly funnelform, somewhat exserted from involucre; lobes oblong-lanceolate, 1–2 mm long, apically acute. Anthers 3.5–4 mm long, anther tails equaling anther-collars; appendages lanceolate; anther-collars balusterform, basally dilated. Style branches 1.8–2 mm long, covered with long marginal papillae and often with a central tuft not conspicuously longer. Achenes ca. 2 mm, glabrous. Pappus 8–10 mm long, red-purple.

Synotis panzhouensis is endemic to southwestern Guizhou, China (Fig. 4); to date, only known from the type population.

Figure 4. 

Record of Synotis panzhouensis.

Growing in mixed forest with other herbs in limestone mountains at an elevation of ~1800 m.

Flowering from late August to September; fruiting October.

The specific epithet is derived from Panzhou, the type locality of the species. The Chinese name is ‘盘州合耳菊 (Pan zhou he er ju)’.

As shown in Figs 1–3, Synotis panzhouensis is similar to S. nayongensis in the oblanceolate or obovate rosulate leaves at the base of synflorescence, the narrow paniculoid thyrse and absence of ray florets. However, we detected significant differences between the two species as listed in Table 1.

Synotis panzhouensis is only distributed in Panzhou, southwestern Guizhou, China, while S. nayongensis is mainly distributed around northwestern Guizhou (Ruan et al. 2020), with its type locality in Nayong, a county located 200 km NE from Panzhou.

From all other species of Synotis, S. panzhouensis is very distinct in the red-purple pappus. According to our observation of the plants in vivo, as well as a critical examination of taxa throughout the genus, most species (~50 spp.) have white pappus. Five species in sect. S. ser. Fulvipapposae C.Jeffrey & Y.L.Chen often have white or stramineous pappus, which is consistent with the descriptions reported by Jeffrey and Chen (1984), Chen (1999) and Chen et al. (2011). The pappus colour of S. vaniotii (Lévl.) C.Jeffrey & Y.L.Chen and S. palmatisecta Y.L.Chen & D.J.Liu were described as rubescent, but this might be the result of inattentive observation, for both of the species were found with white, or rarely pale brown pappus during our field and herbarium observations. It is noteworthy to mention that S. chenopodiifolia (DC.) M.Tang, C.Ren & Q.E.Yang, a species always reported with brown or yellow pappus, has been reported with a dark purple pappus in a population in Gyirong County (Tang et al. 2014), but such variation is rather atypical in the species. Synotis chenopodiifolia is a plant to 80–180 cm with triangular-ovate or triangular-hastate leaves and a capitulum with 5 phyllaries, 2 or 3(–4) disk florets, and it obviously differs from the leaf characters and capitulum characters as seen in S. panzhouensis.

Morphologically, following the characters and delimitation of Jeffrey and Chen (1984) and Tang (2014), S. panzhouensis is best referred to Synotis sect. Synotis ser. Synotis due to the leaves gathered at the apex of the vegetative stem and its terminal inflorescence.

Synotis panzhouensis was found in a single location with an extremely small population in Panzhou, southwestern Guizhou, China. Due to the remote distance and difficult and dangerous accessibility to the type locality, the population was not disturbed by human activity and currently appears to be growing very well. However, according to our observation, the population comprises no more than 100 plants, and with a small geographical range of no more than 1000 m², we recommend that S. panzhouensis be categorized as Critically Endangered (CR) using criteria B and C following the IUCN Red List categories (IUCN 2019).