Stems to 2 (-5) m tall. Leaves 60-130 cm long, flat (not keeled) in section (opposing pinnae inserted at 180° on rachis), with 210-410 pinnae, dark green, semi-glossy. Petiole 18-30 cm long, spinescent for 10-50% of length. Median pinnae 5-12 cm long, 2-4 mm wide, to 2.5-4 mm wide at base, inserted at 70-90° to rachis, 4-6 mm apart, tomentose; margins strongly recurved; midrib flat above, raised below. Cataphylls narrowly triangular, soft, 3-6 cm long. Pollen cones narrowly ovoid to fusiform, 25-30 cm long, 5-7 cm diam., orange to orange-brown. Microsporophyll lamina 25-30 mm long, 8-10 mm wide; apical spine 7-10 mm long. Megasporophylls 12-18 cm long, with 4-6 ovules; lamina lanceolate to ovate, 20-25 mm long, 15-20 mm wide, regularly dentate with 26-36 lateral spines, 2-4 mm long and 1 mm wide; apical spine 6-10 mm long. Seeds 25-31 mm long, 23-30 mm wide.
Although originally described from limestones and named accordingly, this species occurs in various often non-calcareous substrates such as sandstones, sandy alluvium and aluminous schists.
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