Etymology:
from the Latin clivis, a cliff, and the Latin suffix,
-cola, a dweller, in reference to the habitat.
Literature: Tang et al. 1997. Illustrations: Hill & Yang 1999. Historical notes: Although widespread and abundant, this species remained unnamed until 1998. Previous regional treatments placed it in either C. pectinata or C siamensis. Considerable variation occurs across its range, both within and between populations, but it is fairly clearly a single species. Two geographically separated subspecies are recognised. Male sporophylls less than 25 mm long -- A. subsp. clivicola Male sporophylls more than 25 mm long -- B. subsp. lutea A. Cycas clivicola subsp. clivicola Distinguishing features: the smooth trunks and relatively small male cones with very small microsporophylls and thickened axes distinguish this species within Thailand. Distribution and habitat: a common species on limestone outcrops, throughout southern Thailand. Plants are most often rooted in clefts and crevices in near-vertical cliffs, in full sun and often with no soil at the roots. This species is best seen on some of the small island outcrops, eg. near Phang Nga (c. 8°19'N 98°29'E) or Pak Meng (c. 7°28'N 99°18'E), but also occurs on inland limestone mountains. It is also common on Langkawi and in Perlis state in Malaysia, and has recently been nominated as the keynote species for the Perlis State Park national park and conservation area. Although widespread and abundant, this species has remained until now unnamed. Considerable variation occurs across its range, both within and between populations, but it is fairly clearly a single species. Conservation status: abundant and widespread in generally inaccessible sites. Not regarded as threatened. IUCN (1994) Red List status LR nt. B. Cycas clivicola subsp. lutea
K.D. Hill, Brittonia 51: 64, fig. 8e,f,i (1999).
Distinguishing features: subsp. lutea differs from subsp. clivicola in the larger male cones with longer and broader sporophylls. Subsp. lutea tends to display distinctly yellow smooth trunk, a feature shared with C. pectinata, whereas subsp. clivicola has a generally grey trunk. Distribution and habitat: a relatively frequent taxon, growing in full sun on limestone outcrops. Populations were examined, west of Ban Nam Sae (at c. 12°45'N 101°39'E), NE of Klaeng, and near Aranyaprathet, near the Cambodian border about 150 km to the north-east. Also common in gardens in that area, and in cultivation outside of Thailand as `species Araipathet'. Conservation status: although under severe pressure from plant collectors in some areas, this subspecies is still numerous in some extremely inaccessible sites. It is not regarded as threatened. IUCN (1994) Red List status LR nt. Etymology: from the Latin luteus, yellow, pertaining to the yellow trunks.
Description:
Stems arborescent, to 8 m tall, 12-16 cm diam. at narrowest point; 45-100 leaves in crown. Leaves bright green or grey-green (when young), semiglossy, 70-165 cm long, slightly keeled or flat (not keeled) in section (opposing leaflets inserted at 150-180° on rachis), with 90-220 leaflets, with white tomentum shedding as leaf expands; rachis frequently terminated by a spine 2-30 mm long. Petiole 15-55 cm long (12-35% of total leaf), petiole glabrous, spinescent for 0-80% of length. Basal leaflets not gradually reducing to spines, 50-200 mm long. Median leaflets simple, weakly discolorous, 90-260 mm long, 5-11 mm wide, inserted at 45-80° to rachis, decurrent for 3-9 mm, narrowed to 1.5-4 mm at base (to 25-50% of maximum width), 7-16 mm apart on rachis; median leaflets section flat; margins flat to slightly recurved; apex acute, spinescent; midrib raised above, raised below. Cataphylls narrowly triangular, soft, pilose, 50-80 mm long, articulated. Pollen cones narrowly ovoid, yellow to brown or green, 25-50 cm long, 8-11 cm diam.; microsporophyll lamina firm, not dorsiventrally thickened, 19-35 mm long, 10-19 mm wide, fertile zone 17-30 mm long, sterile apex 2-6 mm long, level, apical spine prominent, sharply upturned or gradually raised, 5-16 mm long. Megasporophylls 12-22 cm long, yellow-tomentose to grey-tomentose; ovules 2-4, glabrous; lamina orbicular, 70-140 mm long, 45-95 mm wide, deeply pectinate, with 24-54 soft lateral spines 25-40 mm long, 1.5-4 mm wide, apical spine distinct from lateral spines, 20-75 mm long, 3-8 mm wide at base. Seeds flattened-ovoid, 35-39 mm long, 26-35 mm wide; sarcotesta orange to yellow, not pruinose, 3-4 mm thick; fibrous layer present; sclerotesta smooth. Spongy endocarp absent.
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