1Eublechnoid: sterile and fertile fronds similar on adaxial surface; fertile pinnae either the same width as the sterile or almost so; sorus linear, close to and parallel to the costa but not completely covering the abaxial face leaving a wing of photosynthetic surface
1'Lomarioid: sterile and fertile fronds distinctive on the adaxial surface; fertile pinnae much narrower than the sterile pinnae; sorus linear, close to and parallel to costa but covering the abaxial face and leaving little or no photosynthetic surface
2Stipes and rhachis with spine-like outgrowths
2'Stipes and rhachis without spine-like outgrowths
3Pinnae reduced to small or minute auriculate lobes at the lamina base
3'Pinnae not reduced to auriculate lobes at the lamina base
4Sori often enlarged to overlap or cover the costa and at maturity may obscure the abaxial costal surface; pinnae apices acuminate; fronds of juvenile plants pinna­tifid
4'Sori rarely enlarged to overlap or cover the costa or costal surface; pinnae apices usually attenuate; fronds of juvenile plants entire to lobed
5Pinnae articulated with a characteristic socket joint at the rhachis; mature fronds rarely exceeding 100 cm in length; sterile and fertile pinnae 0.5-1.6 cm wide
5'Pinnae without a socket joint at the rhachis; mature fronds frequently exceeding 100 cm in length; sterile and fertile pinnae 0.7-2.5 cm wide, fertile usually in the narrower range
6Sterile pinnae fully or almost fully adnate to the rhachis for entire length of the la­mina
6'Sterile pinnae free at rhachis, at least on basal part of lamina
7Lamina margins either not dentate or if so only towards pinna apices; lamina pinnate or pinnatisect
7'Lamina with conspicuously dentate margins; lamina either pinnate or bipinnate
8Lamina veins, costae and rhachis, and sometimes the stipe, with fine straight uniseriate hairs; basal pair of pinnae semi-adnate, falcate and sometimes also deflexed
8'Lamina without such hairs; basal pair of pinnae not as above
9Sterile pinnae reducing to adnate lobes towards the base of the lamina; only dissected fronds known to occur
9'Sterile pinnae or pinnules adnate to rhachis with bases broadening to lobes or wings of leaf tissue; both entire and dissected fronds known to occur
10Sterile pinnae not obviously falcate; margins crenate to finely serrate and may be dentate towards the pinna apices; scales of the rhizome and basal stipe black, concolorous, entire, shiny and with finely acuminate apices
10'Sterile pinnae slightly to distinctly falcate; margins mostly entire; scales of rhizome and basal stipe dark red-brown, shortly acuminate, some with paler margins
11Continuous wing of lamina extending down rhachis below basal pinnae
11'Discontinuous wing of lamina tissue, or lobes, extending down rhachis below basal pinnae
12Adaxial stipe (and sometimes both surfaces of stipe, rhachis, and costae) deeply pigmented purple-black
12'Adaxial stipe, rhachis, and costae not deeply pigmented
13Lamina bipinnate to bipinnatisect; caudex 2-3 cm diam., erect, exceptionally up to 200 cm high, forming a miniature tree-fern
13'Lamina pinnate to pinnatisect; caudex 1-2 cm diam., and semi-erect often sprawling on the forest floor
14Sterile pinnae margins strongly and persistently revolute; lamina densely and persistently scaly throughout with dark mahogany coloured scales intermingled with irregular lanuginose material
14'Sterile pinnae margins either not revolute or finely revolute; lamina, if scaly, with scales which are relatively thin and pale fawn to ginger-brown
15Scales at base of stipe narrowly elliptic to subdeltoid, acuminate, red or purple-black, sometimes with paler borders; upper stipe and rhachis scales thin, ginger-brown, some with a small dark centre; plants with a creeping rhizome giving rise to a succession of fronds but fronds are tufted at the apex of the rhizome
15'Scales at base of stipe, upper stipe, and rhachis not as above; creeping rhizomes not a conspicuous feature
16Sterile pinnae short (less than 4 cm long), rounded to oblong with obtuse apices
16'Sterile pinnae more than 4 cm long, linear-narrowly elliptic with acute, acuminate or attenuate apices
17Sterile pinnae narrowly elliptic; in larger fronds several basal pairs may be petiolate and deflexed; stipe and rhachis often with conspicuous black pigmented lines on the ridges on either side of the adaxial groove
17'Sterile pinnae oblong-narrowly elliptic, its pinnae sessile, becoming shortly pinnate but not markedly deflexed near the lamina base; stipe and rhachis without black pigmented lines
18Pinnae and rhachis densely and usually persistently scaly; scales broadly deltoid, thin, papery, fawn to mid-brown and often weakly bicolorous and intermingled with paler lanuginose scales and variable uniseriate hairs
18'Pinnae and rhachis either glabrous or with relatively small scales
19Basal fertile pinnae sessile or shortly petiolate, with a distinctive expanded, leafy, sterile zone widening towards the rhachis but not as wide as the pinnae of the sterile fronds
19'Basal fertile pinnae either having no sterile zone, or a very small but not expanded sterile zone, where the pinnae join the rhachis