Investigations of Angiosperms from the Eocene of North America: Juglandaceous Winged Fruits

Abstract

The winged fruits of Engelhardia have been reported in many early Tertiary floras in the northern Hemisphere. Recent systematic revisions of the extant genera, Engelhardia, Oreomunnea, and Alfaroa provide a helpful guide to the study of the fossil fruits. Fruit form, venation, nut septations and flower parts are features that separate the extant Asian Engelhardia from the American Oreomunnea. Four types of fossil winged fruits can be recognized in Middle Eocene sediments of southeastern North America: Engelhardia, Paraoreomunnea gen. n., Paleooreomunnea gen. n., and Pararengelhardia. Both Paleooreomunnea and Paraengelhardia represent extinct lines; no living forms have similar winged fruits. The fossil fruits of Engelhardia and Paraoreomunnea are similar to the fruits of extant Engelhardia and Oreomunnea, respectively. The fossil taxa reported in this paper were sympatric. The present allopatric distribution of Engelhardia and Oreomunnea is the result of Neogene regional extinctions. Engelhardia and Oreomunnea have probably been distinct genera since early Paleogene time.