Platanaceae are of special interest because of their proposed relationships within the basal eudicots and because of the presence of well-preserved reproductive structures from the Cretaceous with proposed platanaceous affinities. A better understanding of the reproductive architecture of extant taxa is needed for comparative and phylogenetic purposes. This study of extant Platanaceae examined inflorescence architecture and floral development. The data are compared to those from fossil platanoids and are interpreted in a phylogenetic context to provide hypotheses of morphological transformation within this lineage. The subunits are arranged in alternating whorls.
Staminate flowers are generally tetramerous, but there is variability.
The staminate flowers, subtended by a diminutive bract, are composed of single whorls each of tepals and of antetepalous stamens. The tepals are suppressed after initiation. Integration of this information with that from fossils provides a unique perspective regarding the modifications of reproductive structures in Platanaceae. The subunitary divisions of the inflorescence of extant members are not found in Cretaceous fossils, but are present in fossils from different Tertiary epochs. Likewise, Cretaceous flowers have uniform numbers of parts, whereas those from the Tertiary have a higher degree of variability in merosity and are therefore more similar to extant species.