From the natural occurrence of this species in Yunnan Province, China, with
the Latin termination -ensis, place of origin.
Cheng, Fu & Cheng 1975
(as C. siamensis),
(as C. balansae).
Cheng, Fu & Cheng 1975 (as C. siamensis), Wang 1996 (as C. balansae).
Chinese authors have misapplied the name C. siamensis to this taxon
(Cheng, Fu & Cheng 1975).
The larger and more numerous leaves with more numerous leaflets and the
larger male cones distinguish this species from C. simplicipinna
and C. balansae. It is one of the complex of closely related
acaulescent taxa with soft pollen cones, loose, freely peeling sarcotesta
lacking a fibrous layer and rugose sculpting of the sclerotesta (Section
Stangerioides) that is distributed through northern Vietnam, Laos,
northern Thailand and Yunnan and Guangxi in southern China.
Distribution and habitat:
Locally frequent although not in dense stands, in more sheltered sites in deep
shade in tall closed evergreen forests, mainly in the Sichuangbanna region of
southern Yunnan province, China. Probably also in Laos and Myanmar.
Not considered to be seriously at risk.
IUCN (1994) status LR, cd.
Stems acaulescent, 12-20 cm diam. at narrowest point; 2-10 leaves in crown.
Leaves deep green, highly glossy, 210-350 cm long, slightly keeled or flat (not keeled) in section (opposing leaflets inserted at 170-180° on rachis), with 90-190 leaflets, with white tomentum shedding as leaf expands; rachis consistently terminated by paired leaflets. Petiole 85-145 cm long (35-50% of total leaf), petiole glabrous, spinescent for 85-100% of length. Basal leaflets not gradually reducing to spines, 120-230 mm long.
Median leaflets simple, strongly discolorous, 250-400 mm long, 15-19 mm wide, inserted at 60-85° to rachis, decurrent for 5-8 mm, narrowed to 2.5-4 mm at base (to 17-25% of maximum width), 16-27 mm apart on rachis; median leaflets section flat; margins undulate; apex softly acuminate, not spinescent; midrib raised above, flat below.
Cataphylls narrowly triangular, soft, pilose, 50-80 mm long, articulated.
Pollen cones fusiform, yellow, 25-60 cm long, 6-10 cm diam.; microsporophyll lamina soft, not dorsiventrally thickened, 25-40 mm long, 14-19 mm wide, fertile zone 22-36 mm long, sterile apex 2-4 mm long, level, apical spine absent.
Megasporophylls 8-14 cm long, brown-tomentose; ovules 2-4, glabrous; lamina ovate, 50-70 mm long, 30-70 mm wide, deeply pectinate, with 12-22 soft lateral spines 15-35 mm long, 1.5-2 mm wide, apical spine distinct from lateral spines, 12-30 mm long, 2-5 mm wide at base.
Seeds ovoid, 25-27 mm long, 20-22 mm wide; sarcotesta yellow, not pruinose, 2 mm thick; fibrous layer absent; sclerotesta verrucose. Spongy endocarp absent.