Taraxacum ceratosectum Kirschner & Štěpánek, 2023

Kirschner, Jan & Štěpánek, Jan, 2023, A taxonomic revision of Taraxacum sect. Dissecta, a continental steppe group common in Siberia and adjacent regions of Central Asia, Phytotaxa 590 (1), pp. 1921-1935 : 1921-1935

21. Taraxacum ceratosectum Kirschner & Štěpánek , sp. nov.

Type:—[ RUSSIA, Transbaicalia, Republic of Buryatia] Lake Baikal, Barguzinsky Khrebet, mouth of the Boľshoi Chivyrkhui River [ca. 53° 59’ 13” N, 109° 33’ 30” E], 460 m, 19 Jul 1993, J. Danihelka, cultivated as JK 3660 ( PRA, no. det. 35841, holotype; isotype: PRA, no. det. 36679) .

Etymology:—Derived from the intermediate position between T. sect. Dissecta and T. sect. Borealia (= T. sect. Ceratophora ).

Diagnosis:—Species Taraxaco subcompacto aemulans sed differt petiolis angustioribus, foliis subglabris, acheniis longioribus, pyramide subcylindrica, achenii corpore longissime spinuloso, spinulis tenuibus saepe subarcuatis, necnon rostro conspicue longiore.

Plants small, usually to 9–12 cm tall. Petiole usually narrowly winged, subglabrous to sparsely arachnoid, usually purplish; plant base with whitish hairs, tunic not seen on cultivated material. Leaves in several rosettes on a root head, slightly greyish mid-green, subglabrous, linear-oblong to narrowly oblanceolate in outline, usually 5–10 × 1.5–2 cm, of variable shape, some, usually the outer leaves almost undivided, proximally lobulate (with recurved acute toothlike lobes), or distally undivided (irregularly dentate) and proximally pinnatilobed, or wholly pinnatisect, with 2–4 (5) pairs of ± patent to recurved, narrowly triangular or narrowly deltoid lateral segments with distal margin straight to concave, entire or with a single tooth, proximal margin usually ± straight, entire or with a basal tooth; terminal segment flat deltoid-triangular, ± entire, or elongated-triangular, with numerous acute subrecurved teeth and lobules; interlobes short, usually 2–4 (–5) mm wide, entire or denticulate; mid-vein most often purplish. Scapes often growing lateral to leaf rosettes, brownish green or suffused purplish basally, arachnoid, ± overtopping leaves. Capitulum yellow, ca. 2.5 cm wide. Involucre ± olivaceous-green, 8–9 mm wide and rounded at base. Outer phyllaries 13–15 (–16), ± ovate to ovate-lanceolate, appressed to loosely appressed, ± not imbricate, 6–8 × 2.8–4.2 mm, with contrasting colours, a dark to blackish middle strip ca. 1 mm wide, bordered with a pale yellow-green zone 0.8–1.5 mm wide, and a membranous to whitish membranous border 0.3–0.5 mm wide, margin sparsely ciliate, apex darker, marginally suffused purple, black corniculate (at least in later capitula); inner phyllaries 11–13 mm long, flat to corniculate. Outer ligules ± flat, striped blackish purple outside, inner ligule teeth ± purple. Stigmas dirty yellow to greyish yellow, with mixed hyaline and grey pubescence outside. Pollen sparsely present, pollen grains irregular in size. Achenes reddish light brown, 3.7–4.0 × ca. 1.0 mm, body spinulose and squamulose in upper 1/4, the uppermost spinules often 0.3–0.4 mm long, and sometimes arcuate-subpatent, subabruptly narrowing into a subcylindrical cone 0.8–0.9 × ca. 0.3 mm; beak 9–10 mm long, pappus 5.5 mm long, yellowish white. – Agamosperm. – Fig. 23 .

Diagnostic notes:—The general habit intermediate between the sections Dissecta and Borealia , the ovate and broadly, conspicuously bordered outer phyllaries with blackish corniculation, and the reddish light brown achenes represent a unique character combination. The arrangement of leaves in several rosettes, and the scapes lateral to the rosettes point to T. sect. Borealia .

Distribution and habitat:— Taraxacum ceratosectum is known from a single locality in the Barguzin Range, Buryatia, where it grows in gravelly habitats along the river.

Figures

FIGURE 23. Taraxacum ceratosectum. A, General habit; B, Achenes (both from PRA, no. det. 35841, holotype).