PRIMITIVE MIMOSOID FLOWERS FROM THE PALEOCENE-EOCENE AND THEIR SYSTEMATIC AND EVOLUTIONARY IMPLICATIONS

Compressed mimosoid inflorescences from a Paleocene-Eocene boundary locality in western Tennessee are the earliest fossil evidence of the subfamily. The discovery confirms the antiquity of a suite of characters that has been considered primitive based on the comparative morphology of modern mimosoids. The fossil characters are also consistent with the suggested close relationship (ancestral or sister group) between the subfamily Mimosoideae and the Dimorphandra group of the tribe Caesalpinieae (subfamily Caesalpinioideae). These flowers show little change in morphology or size in the basal to Upper Eocene interval.