Etymology:
From the Latin arenarius, pertaining to sand, with the
suffix -cola, a dweller or inhabitant, in reference to
the occurrence in broken sandstone country.
Illustration: Hill 1993, fig. 1. Distinguishing features: Distinguished among Australian species by the non-keeled leaves, the fusiform to elongate-ovoid microsporangiate cones, and the narrow, non-glaucous leaflets with recurved margins and persistent brown tomentum beneath. This species is most similar to C. calcicola Maconochie, also from the Northern Territory, sharing the small, narrow microsporangiate cone and the persistent tomentum on the undersurfaces of the leaflets, but differing in having fewer leaflets per leaf (180--270), and wider leaflets (4.0--6.5 mm wide) which taper more gradually to the apex and are less crowded (spaced at 8--14 mm on the rachis). C. pruinosa Maconochie from Western Australia has narrow leaflets with recurved margins and a narrow microsporangiate cone, but the leaflets of C. arenicola are not glabrous at maturity and the cones are much shorter (c. 25 cm long). No other Australian species shares the persistent tomentum on the undersurfaces of the leaflets. In addition, all Australian species except C. arenicola, C. calcicola and C. pruinosa have more nearly ovoid microsporangiate cones. Distribution and habitat: C. arenicola occurs on sandy soils on screes derived from siliceous sandstone in rugged and broken country of the upper reaches of the East Alligator and Liverpool Rivers. This species occurs in an exremely remote area and has rarely been collected, and is likely to be more widely distributed in that area. Conservation status: Not threatened. Description:
Stems arborescent, to 1.5(-2.5) m tall, 15-20 cm diam. at narrowest point. Leaves bright green, semiglossy, 90-160 cm long, flat (not keeled) in section (opposing leaflets inserted at 160-180° on rachis), with 180-200 leaflets, with brown tomentum persistent below; rachis consistently terminated by a spine. Petiole 25-35 cm long, pubescent, spinescent for 50-100% of length. Basal leaflets gradually reducing to spines. Median leaflets simple, strongly discolorous, 90-190 mm long, 4.5-6.5 mm wide, inserted at 60-90° to rachis, decurrent for 2-3 mm, narrowed to 3-5 mm at base (to 70-80% of maximum width), 9-14 mm apart on rachis; median leaflets section flat; margins recurved; apex acute, spinescent; midrib flat above, raised below. Cataphylls linear, soft, pilose, persistent. Pollen cones narrowly ovoid to fusiform, orange, 25 cm long, 9 cm diam.; microsporophyll lamina firm, not dorsiventrally thickened, 25-30 mm long, 6-9 mm wide, fertile zone 15-20 mm long, sterile apex 6 mm long, level, apical spine prominent, sharply upturned, 5 mm long. Megasporophylls 15-20 cm long, grey-tomentose and brown-tomentose; ovules 4-6, glabrous; lamina lanceolate, 30-40 mm long, 14-18 mm wide, obscurely or regularly dentate, with 18-26 pungent lateral spines 0-1 mm long, 1 mm wide, apical spine distinct from lateral spines, 8 mm long. Seeds flattened-ovoid, 28-32 mm long, 25-29 mm wide; sarcotesta orange-brown, slightly pruinose, 1.5-3 mm thick; fibrous layer absent; sclerotesta smooth. Spongy endocarp absent.
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