Under the Cronquist system, only the Apiaceae and Araliaceae were included here, and the restricted order was placed among the rosids rather than the asterids. The Pittosporaceae were placed within the Rosales, and many of the other forms within the family Cornaceae. Pennantia was in the family Icacinaceae. In the classification system of Dahlgren the families Apiaceae and Araliaceae were placed in the order Ariales, in the superorder Araliiflorae (also called Aralianae).
The present understanding of the Apiales is fairly recent and is based upon comparison of DNA sequencesbyphylogenetic methods.[6] The circumscriptions of some of the families have changed. In 2009, one of the subfamilies of Araliaceae was shown to be polyphyletic.[7]
The largest and obviously closely related families of Apiales are Araliaceae, Myodocarpaceae and
Apiaceae, which resemble each other in the structure of their gynoecia. In this respect however, the Pittosporaceae is notably distinct from them.[8]
Typical syncarpous gynoecia exhibit four vertical zones, determined by the extent of fusion of the carpels. In most plants, the synascidiate (i.e. "united bottle-shaped") and symplicate zones are fertile and bear the ovules.[9] Each of the first three families possess mainly bi- or multilocular ovaries in a gynoecium with a long synascidiate, but very short symplicate zone, where the ovules are inserted at their transition, the so-called cross-zone (or "Querzone").[8]
In gynoecia of the Pittosporaceae, the symplicate is much longer than the synascidiate zone, and the ovules are arranged along the first. Members of the latter family consequently have unilocular ovaries with a single cavity between adjacent carpels.[8]
^Winkworth, Richard C.; Lundberg, Johannes; Donoghue, Michael J. (2008). "Toward a resolution of Campanulid phylogeny, with special reference to the placement of Dipsacales". Taxon. 57 (1): 53–65.
^Tank, D. C.; Donoghue, M. J. (2010). "Phylogeny and Phylogenetic Nomenclature of the Campanulidae based on an Expanded Sample of Genes and Taxa". Systematic Botany. 35 (2): 425. doi:10.1600/036364410791638306. S2CID27856073.
^Nicolas, A. N.; Plunkett, G. M. (2009). "The demise of subfamily Hydrocotyloideae (Apiaceae) and the re-alignment of its genera across the entire order Apiales". Molecular Phylogenetics and Evolution. 53 (1): 134–151. doi:10.1016/j.ympev.2009.06.010. PMID19549570.
^Pankhurst, R. J. (1992). Morphology of flowers and inflorescences (1st pbk. ed.). Cambridge, England: Cambridge University Press. pp. 153–155. ISBN9780521438322.
