Taraxacum obscurum Stepanek & Kirschner 2023, sp. nov.
Creators: name: Kirschner, Jan
name: Štěpánek, Jan
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Asterales
Asteraceae
Taraxacum
Taraxacum obscurum

description: 16. Taraxacum obscurum Štěpánek & Kirschner, sp. nov.   
 Type:—[RUSSIA, Irkutskaya oblast]. Sibiria merid., urbs Bratsk: ad ripam sinistram lacus structilis “Bratskoe More” (ca. 2 km situ a vallo) prope partem Padun urbis Bratsk, 28 Oct 1985, J. Kirschner & J. Štěpánek, cultivated as JŠ 2556, collected in 1988 (PRA, no. det. 36956, holotype; isotype: PRA, no. det. 36954).   
 Etymology:—Dark, unclear, hidden.   
  Diagnosis:—Plantae insignes acheniis mediocriter brunneis vel saturate brunneis, pyramide tenui ± cylindrica, antheris polline carentibus, phyllariis involucralibus exterioribus adpressis, apice laxe adpressis, late ovatis vel ovatis, obscure griseo-viridibus, marginibus pallidis angustissimis, segmentis et interlobiis foliorum saepissime integris.    
Plants small, usually 6–8 cm tall, later (fruiting plants) to 14 cm. Petiole narrow, unwinged or narrowly winged, usually 2–2.5 cm long, most often suffused purplish; root often with several heads, tunic developed, dark brown, plant base with dense greyish or light brownish arachnoid hairs among petiole bases. Leaf rosette compact, with numerous leaves. Leaves erect-patent to patent, ± glabrous or subglabrous (hairs scattered along mid-vein adaxially), not spotted, rarely with inconspicuous sparse little brown-purple spots (visible only on late leaves), narrowly elliptical to narrowly oblanceolate, usually 5–7 × 1.5–2.5 cm, regularly pinnatipartite to pinnatisect; lateral segments in 3 (4) pairs, usually subrecurved to patent, sometimes hamate-subrecurved, rarely pointing forwards, usually 5–9 mm long, 2–5 mm wide at base, usually ± abruptly narrowed from a broad base to an elongated to lingulate, acute to acuminate distal part, distal margin usually sigmoid, entire, proximal margin straight to subconvex, entire; terminal segment relatively small, broadly triangular to triangular in outline, often trilobed, usually 5–12 × 9–14 mm, terminal part usually broadly lingulate, obtusely acute, entire, basal lobules, usually patent, triangular to narrowly lingulate, entire; interlobes relatively broad, usually 2–4 × 2.5–5 mm, not bordered or only very indistinctly so, margin distally ± raised, entire or with a single little thin tooth. Scapes irregularly arachnoid, ± pale green, suffused purplish at base, later purplish also below capitulum, usually 4–7 cm long, ± equalling leaves. Capitulum yellow, flat to subconvex, small, 2–2.5 cm wide. Involucre ca. 7 mm wide and rounded to subtruncate at base. Outer phyllaries 11–15, appressed (apical 1/3 loosely appressed), relatively short, reaching ½ of the inner phyllaries, broadly ovate to ovate (the uppermost ones often lanceolate), ± not imbricate, (4–) 5.5–6.5 × (2.5–) 3–4 mm, surface ± evenly dark olivaceous-green (almost black-green when dry), with an abrupt transition in a ± translucent, dirty whitish border 0.1–0.25 mm wide, margin initially densely ciliate distally, later ± glabrescent, apex often minutely corniculate; inner phyllaries 8–10 mm long, of slightly unequal width, with a dark, often minutely corniculate apex. Outer ligules flat, narrowly striped greyolivaceous outside, apical teeth brownish, inner ligule teeth yellow. Stigmas light to medium discoloured, greyish yellow-green, hairs of pubescence often dark distally. Pollen absent.Achenes ± medium dark brown, 3.7–4.4 × 0.9–1.0 mm, achene body ± densely spinulose (spinules suberect to erect-patent, up to 0.35 mm long) in upper 1/3–1/4, otherwise tuberculate, lateral ridges moderately distinct, serrulate in upper 1/3–1/2, body subgradually narrowing into a subcylindrical to cylindrical cone 0.6–1.0 mm long; beak 6–7 mm long, pappus whitish to dirty white, 5 mm long. – Agamosperm. – Fig. 18.  
 Diagnostic notes:—The medium dark brown achenes, the ovate outer phyllaries with a very narrow pale border, and the absence of pollen are diagnostic. In addition, distinct, long spinules on the achene body, and usually a total absence of teeth or lobules make a difference from T. spadiceum. Relatively dark outer phyllaries with a narrow but distinct paler border recall T. dorchocarpum of T. sect. Erythrocarpa (Štěpánek & Kirschner 2022).   
 Distribution and habitat:— Taraxacum obscurum is confined to a single macrolocality along the western shore of the Bratsk Reservoir on River Angara. The relatively dry, denuded, sandy and gravelly shore habitat with sparse vegetation is rich in dandelions, and T. sect. Dissecta is richly represented there.
description: Published as part of 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, pp. 1921-1935 in Phytotaxa 590 (1) on pages 1921-1935, DOI: 10.11646/phytotaxa.590.1.1, http://zenodo.org/record/7780271