Acer section Palmata, the group of maple trees that includes the horticulturally important Japanese maple, Acer palmatum, has usually been considered to be among the most primitive sections of Acer. Species in this section have few bud scales and terminal inflorescences, which place it close to Dipteronia, the presumed sister group of the genus. Recent molecular studies using a limited number of taxa also seem to support the basal placement of section Palmata in Acer. However, the stratigraphic record does not fully support this hypothesis. All modern species in the section Palmata occur in eastern Asia, except the single western North American species Acer circinatum. Acer section Palmata can be divided into three series: Palmata, Sinensia, and Penninervia. The latter contains species with entire margined, unlobed leaves, which are not known from the fossil record. Series Palmata has distinctive many-lobed leaves with serrate margins. Leaves of this type are apparently lacking in the fossil records of North America and Europe, but are found in Asia beginning in the Miocene. Acer series Palmata has been suggested to be a derived subset of the paraphyletic series Sinensia. Species in the series Sinensia have 3- to 7-lobed leaves with serrate or entire margins. However, no fossils of this series have been reported. It is possible that leaves of species in series Sinensia may have been misidentified, since they are similar to the leaves of species in many other Acer sections. There are species in other sections of Acer that date back to the Eocene and perhaps the Paleocene in both North America and Asia. Therefore, the fossil record suggests that the section Palmata may be a relatively recent, derived group rather than one of the basal Acer sections, and that the dispersal of the section between North America and Asia occurred in the late Tertiary.

Key words: Acer, Asia, North America, paleobotany, Palmata, Tertiary