The Zamiaceae are a family of
cycads that are superficially palm or fern-like. They are divided into two subfamilies with eight genera and about 150 species in the tropical and subtropical regions of
Africa,
Australia and
North and
South America.
The Zamiaceae, sometimes known as zamiads, are
perennial, evergreen, and
dioecious. They have subterranean to tall and erect, usually unbranched, cylindrical stems, and stems clad with persistent leaf bases (in Australian genera).
Their
leaves are simply pinnate, spirally arranged, and interspersed with cataphylls. The leaflets are sometimes dichotomously divided. The leaflets occur with several sub-parallel, dichotomously branching longitudinal veins; they lack a mid rib.
Stomata occur either on both surfaces or undersurface only.
Their roots have small secondary roots. The
coralloid roots develop at the base of the stem at or below the
soil surface.
Male and female
sporophylls are spirally aggregated into determinate
cones that grow along the axis. Female sporophylls are simple, appearing peltate, with a barren
stipe and an expanded and thickened lamina with 2 (rarely 3 or more) sessile
ovules inserted on the inner (axis facing) surface and directed inward. The seeds are angular, with the inner coat hardened and the outer coat fleshy. They are often brightly colored, with 2
cotyledons.
One subfamily, the Encephalartoideae, is characterized by spirally arranged sporophylls (rather than spirally
orthostichous), non-articulate leaflets and persistent leaf bases. It is represented in Australia, with two genera and 40 species.
As with all cycads, members of the Zamiaceae are
poisonous, producing poisonous
glycosides known as cycasins.
The former family Stangeriaceae (which contained Bowenia and Stangeria) has been shown to be nested within Zamiaceae by phylogenetic analysis.[1]
The family first began to diversify during the
Cretaceous period.[2][3]
^Uzunova, K.; Palamarev, E.; Kvacek, Z. (2002). "Eostangeria ruzinciniana (Zamiaceae) from the Middle Miocene of Bulgaria and its relationship to similar taxa of fossil Eostangeria, and extant Chigua and Stangeria (Cycadales)". Acta Palaeobotanica. 41 (2): 177–194.