Aphanopetalum is a small genus of two species of scrambling shrubs and twining vines native to Australia, comprising the entirety of the family Aphanopetalaceae. The family is placed in the order Saxifragales, though its taxonomic history has been unsettled: the genus was formerly included in Cunoniaceae and then assigned its own family within Oxalidales before being moved to its current placement in Saxifragales.
Plants in the genus are characterised by lenticellate stems that scramble or twine through surrounding vegetation, with opposite, serrate leaves and minute stipules. The flowers are reduced and essentially petalless, instead bearing four conspicuous white sepals that persist and enlarge as the single-seeded fruit develops. Flowers and inflorescences are borne in axillary positions.
The genus contains two species with restricted Australian distributions: Aphanopetalum resinosum (gum vine), which ranges from north-eastern Victoria through New South Wales to northern Queensland, and Aphanopetalum clematideum, which is endemic to limestone cliffs of south-western Australia. A. resinosum is the type species of both the genus and the family.
Distribution
The genus is endemic to Australia. Aphanopetalum resinosum (gum vine) occurs in eastern Australia from north-eastern Victoria through New South Wales to northern Queensland. Aphanopetalum clematideum is restricted to limestone cliffs of south-western Australia.
Taxonomy Notes
Aphanopetalum has had a complex taxonomic history. The genus was originally included within Cunoniaceae (order Oxalidales), then segregated into its own monotypic family Aphanopetalaceae while remaining in Oxalidales. Molecular phylogenetic work subsequently relocated Aphanopetalaceae to Saxifragales, where it is currently accepted by GBIF and other authorities.
