From 7.5 to 18 m tall, the trunks are clustering and armed with small spines, usually with stilt
roots at the base.
A. aculeata tends to be smaller, with trunk diameters around 10 cm,
M. armata and
M. macroclada trunks reach 25 – 30 cm; all three retain persistent leaf bases towards the top of the stem. Each 1 m
leaf of a mature tree is palmate with a brief costa, borne on a long petiole, and divided into numerous, deep segments; leaves of juvenile trees are flattened and much less divided. Bright to deep green, the foliage has silvery, glaucous undersides. The
inflorescence is usually solitary, interfoliar, with male and female units represented in separate plants. The round
fruit is usually one-
seeded and covered in red to brown scales with a thick, fleshy mesocarp. The seed is spherical or oblong, basally attached, with an elongated apical knob. ==Distribution and habitat==