Timonius denigricans P. K. Hoo 2023, sp. nov.
Creators: name: Hoo, Pui Kiat
name: Sugumaran, Manickam
name: Wong, Khoon Meng
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Gentianales
Rubiaceae
Timonius
Timonius denigricans

description: Timonius denigricans P.K.Hoo, sp. nov. (Fig. 5)
Distinct among the Malay Peninsula Timonius species in having black (vs grey-brown) bark, and most similar to T. flavescens except in having densely (vs sparsely) hairy hypanthium, staminate inflorescences with 3 (vs 5–9(–18), very rarely 3) flowers, smooth (vs shagreened) lower leaf lamina surface, and green (vs purplish) midrib and secondary veins on lower leaf surface in fresh material.
Type:— Peninsular Malaysia, Terengganu, Jabi, Gunung Tebu, Sungai Chabang Dua, 2 June 1974, Md. Shah, Ahmad & Mahmud MS 3317 (holotype SING; isotypes KEP, KLU – ♀ Fl, Fru).
Timonius flavescens auct. non Baker, Fl. Mauritius (1877) 144: sensu Wong, Kew Bull. 43 (1988) 504, pro parte, quoad specim. Md. Shah, Ahmad & Mahmud MS 3317 and Loh FRI 13500.
Small tree recorded as up to 12 m tall, 30 cm diameter. Bark black with grey patches, smooth to sometimes scaly. Young twigs densely appressed yellow hairy (the surface mostly obscured). Stipules triangular, imbricate, outer surface densely appressed to ascending yellow hairy becoming distinctly less so along margins. Leaves: petioles 5–15 mm long, 1–2 mm diameter, moderately to completely appressed yellow hairy with scattered ascending hairs (the surface visible among hairs or obscured); blades drying discolorous (dark brown on upper surface, light brown on lower surface); elliptic, 4.5–16 × 2–7.5 cm, length:width ratio 2.3–3, coriaceous; lower lamina surface smooth, sparsely appressed silvery hairy, not silky to the touch, midrib and secondary veins drying brown (green when fresh), densely appressed yellow hairy with scattered ascending hairs and so mostly or completely obscured; upper surface glabrous; base cuneate to attenuate, margins plane, apex acute to cuspidate; secondary veins 5–8 pairs, fading towards leaf margin; tertiary veins on lower surface sub-parallel, immersed in the lamina, clearly visible. Pistillate inflorescence with a solitary flower (known only in bud), peduncles 1.5–2.5 cm long, ca. 1 mm diameter, sparsely appressed yellow hairy with scattered ascending hairs, bracts triangular, entire, ca. 2 × 1 mm, sparsely appressed yellow hairy; hypanthium ca. 2.5 mm long, ca. 3 mm diameter, lobed, densely appressed yellow hairy; calyx tubes 1–1.5 mm long, lobes 4, broadly triangular, less than 0.5 mm long, ca. 2 mm wide, sparsely appressed yellow hairy; mature corolla not seen, in bud ca. 6 mm long, ca. 2.5 mm diameter, densely appressed yellow hairy, lobes 4. Staminate inflorescences with 3 flowers (known only in bud), branching dichasial, peduncles sparsely appressed brown hairy; hypanthium sparsely to densely appressed yellow hairy. Infructescence with a solitary fruit, peduncles 1.5–3.5 cm long, 1–1.5 mm diameter, sparsely appressed yellow hairy; fruits globose to depressed-globose, 7–10 mm long, 8–13 mm diameter, sparsely to densely appressed yellow hairy, with 4 distinct lobes, internal matrix soft with conspicuous air spaces; persistent calyx tube at fruit apex 1.5–2 mm long, sparsely appressed yellow hairy; persistent calyx lobes 4, broadly triangular, ca. 1 mm long, ca. 2.5 mm wide, sparsely appressed yellow hairy, erect; pyrenes ca. 35 per fruit, ellipsoid, with walls less than 0.5 mm thick.
Etymology: —The specific epithet refers to the black bark.
Habitat: —Lowland mixed dipterocarp forest up to 400 m elevation.
Distribution: —Endemic to Peninsular Malaysia where it is known from areas east of the Main Range (Kelantan, Pahang and Terengganu).
Preliminary conservation status: — Timonius denigricans is assessed as Near Threatened (NT). The estimated AOO and EOO are 20 km 2 and 6719 km 2, respectively. However, there is no evidence of continuing decline in AOO, EOO, area of habitat and number of locations. Nevertheless, the lowland forests where the species is found, may be degraded or lost due to future threat such as land-use change.
Additional specimens examined: —PENINSULAR MALAYSIA. Kelantan: Kuala Krai District, Sungai Durian F. R., 7 July 1987, Damahuri & Khairuddin FRI 35982 (KEP – ♀ Fru). Pahang: Pekan District, Lepar F. R., 18 June 1967, Suppiah KEP 108966 (KEP – ♀ Fru). Terengganu: Hulu Terengganu District, Sekayu, Bukit Lanjut F. R., 20 September 1969, Loh FRI 13500 (KEP, SING – ♂ Fl). Setiu District, Bukit Kesing, trail to TM station from SE, 4 June 2022, Hoo HPK 78 (KEP – ♀ Fru).
Notes: —The diagnosis for this species was made by comparing with all Timonius flavescens specimens cited in Wong (1988) but excluding Md. Shah, Ahmad & Mahmud MS 3317 and Loh FRI 13500. Additional specimens not included in Wong (1988) were also examined at KEP and KLU (e.g. Hoo HPK 48, Hoo HPK 49, Remy & Teo KL 4025 and Saw FRI 34342).
description: Published as part of Hoo, Pui Kiat, Sugumaran, Manickam & Wong, Khoon Meng, 2023, Two new species of Timonius (Rubiaceae: Guettardeae) from the Malay Peninsula, pp. 171-182 in Phytotaxa 599 (3) on pages 178-180, DOI: 10.11646/phytotaxa.599.3.4, http://zenodo.org/record/8012553