The APG II system, of 2003, also recognizes this family and assigns it to the order Gunnerales in the clade core eudicots. The family then consists of one or two genera, Gunnera and, optionally, Myrothamnus. The latter may also be segregated as a separate family, Myrothamnaceae. This represents a change from the APG system, of 1998, which firmly recognized two separate families, unplaced as to order. The APG III system recognizes the family Gunneraceae and places Myrothamnus in the separate family Myrothamnaceae; both families are placed in the order Gunnerales in the core eudicots.
Typically a leaf is a thin, flattened organ borne above ground and specialized for photosynthesis, but many types of leaves are adapted in ways almost unrecognisable in those terms: some are not flat (for example many succulent leaves and conifers), some are not above ground (such as bulb scales), and some are without major photosynthetic function (consider for example cataphylls, spines, and cotyledons).
Conversely, many structures of non-vascular plants, or even of some lichens, which are not plants at all (in the sense of being members of the kingdom Plantae), do look and function much like leaves. Furthermore, several structures found in vascular plants look like leaves but are not actually leaves; they differ from leaves in their structures and origins. Examples include phyllodes, cladodes, and phylloclades.