Petrocodon curvitubus J. X. Wei, B. Pan & T. Ding 2025, sp. nov.

Petrocodon curvitubus J. X. Wei, B. Pan & T. Ding sp. nov. Diagnosis. P. curvitubus is florally similar to P. lui and P. tenuitubus. However, it can be distinguished from these by leaf characteristics, with leaves elliptic to oblong-ovate, apex obtuse or slightly acuminate, base cuneate (vs P. lui, ovate or broadly ovate; apex subacute or obtuse, base cordate to shallowly cordate, oblique; vs P. tenuitubus, ovate to orbicular; apex obtuse, base cordate symmetrical or asymmetrical), corollas with purple stripes (vs absent in P. lui and P. tenuitubus), corolla lobes obovate-elliptic to oblong, apex acuminate (vs P. lui, lobes oblong, obovate to suborbicular, apex obtuse; vs P. tenuitubus, lobes narrowly ovate to ovate, apex obtuse), and ovary conical, ca. 2.5 × ca. 0.8 mm (vs P. lui, linear, ca. 3 × 1.5 mm; vs P. tenuitubus, ovoid, 1–2 × 1–1.5 mm) (Table 1). Description. Perennial herbs. Rhizome short and straight, subterete, 1–3.8 cm long, 7.5–9 mm in diameter. Leaves 10–18, basal, alternate, and congested at rhizome apex; petiole terete, adaxially pale green, abaxially pale brown, 2.5–6.4 cm long, 2–2.5 mm in diameter, densely white pubescent. Leaf blade herbaceous, elliptic to oblong-ovate, 2.1–13.3 × 1.1–7.5 cm, apex obtuse or slightly acuminate, base cuneate, margin crenulate, adaxially surface pale green, abaxially grayish green, both surfaces densely white pubescent, lateral veins pinnate 5–8 pairs on each side, adaxially concave, abaxially prominent. Inflorescences 3–6, axillary, 1–5 - branched, cymose, (4 -) 10–16 (- 22) - flowered; peduncles 2.2–6.8 cm long, 2–2.5 mm in diameter, densely white pubescent; bracts 2, linear, opposite, 4–5 × ca. 0.5 mm, outside densely white pubescent, inside glabrous; pedicels 3–8 mm long, 0.3–0.7 mm in diameter, densely white pubescent. Calyx 5 - lobed from base, pale green, lobes linear to triangular, 4–6 × ca. 0.5 mm, outside densely white pubescent, inside glabrous; Corolla pale purple, zygomorphic, 1.8–2.2 cm long, both surfaces sparsely puberulent, with two dark purple longitudinal stripes in the corolla mouth; corolla tube slenderly tubular, strongly curved downwards at base (1–3 mm from the base), then bent forwards, 1–1.3 cm long, 1.5–2.5 mm in diameter at the mouth, 1 mm in diameter at the base, adaxial lip 2 - lobed to near base, obovate-elliptic, 0.5–0.7 cm long, ca. 0.3 mm in diameter, apex acuminate; abaxial lip 3 - lobed to base, oblong, 0.6–1.1 cm long, 2.5–4 mm in diameter, apex acuminate. Stamens 2, adnate about 6 mm from corolla base, glabrous; anthers pale yellow, ca. 1.5 mm long, dorsifixed, cohering apically; filaments ca. 1 mm long, white, glabrous. Staminodes 3, ca. 0.1 long, white, adnate 2.5 mm above corolla base. Disc annular, ca. 0.5 mm high, orange-yellow. Pistil ca. 5.5 mm long, ovary conical, ca. 2.5 mm long, ca. 0.8 mm in diameter, style ca. 3 mm long, ovary and style densely covered with short glandular and eglandular hairs, stigma bilobed, lobes oval, ca. 0.5 mm long. Capsule 0.5–1 cm long, about 2 mm wide, dehiscing 4 - valved. Seeds not seen. Type. China • Guangxi Zhuang Autonomous Region, Baise City, Debao County, Longguang Town, 23 ° 5 ' N, 106 ° 44 ' E, 454 m a. s. l., growing on rock wall at the entrance of karst cave. 26 January 2024, flowering, WJX 001 (holotype: IBK! IBK 00470322), WJX 002 (paratype: IBK! IBK 00470323). Phenology. Flowering from January to March. Etymology. The epithet originates from the strongly curved corolla tube. Vernacular name. Wān Guǎn Shí Shān Jù Tái (弯管石山苣苔), the first two words, “ Wān Guǎn, ” mean the corolla tube is strongly curved, and the following four words, “ Shí Shān Jù Tái, ” mean Petrocodon in Chinese. Distribution and habitat. Petrocodon curvitubus can only be found at its type locality, Longguang Township, Debao, Baise, Guangxi. It grows on a limestone wall at the entrance of a karst cave at an altitude of 454 m. The average annual temperature in Debao County is 19.5 ° C, and the average annual precipitation is 1456.2 mm. Preliminary conservation assessment. Currently, only one population that consists of about 200 mature individuals of P. curvitubus has been discovered. This population is concentrated on the stone wall at the entrance of a karst cave that is located in Longguang Township, Debao, Baise, Guangxi. The area occupied (AOO) is about 100 m 2, which is significantly smaller than the smallest AOO unit of the IUCN (2024) (10 km 2 for Critically Endangered under B 2). Additionally, we also observed that the habitat of P. curvitubus is located near a village and is vulnerable to human activities. Frequent human impacts may lead to a reduction in mature individuals of this species and the decline of the population. According to the IUCN Red List Categories and Criteria (IUCN 2024), the endangered level of this new species is preliminarily assessed as “ Critically Endangered ” [CR, B 2 a, b (iii, v)].