ATTACHED LEAVES, INFLORESCENCES, AND FRUITS OF FAGOPSIS, AN EXTINCT GENUS OF FAGACEOUS AFFINITY FROM THE OLIGOCENE FLORISSANT FLORA OF COLORADO, U.S.A.

Abstract

Specimens showing staminate and pistillate inflorescences attached to branches bearing Fagopsis longifolia (Lesq.) Hollick foliage, from the Oligocene Florissant flora of Colorado, permit a relatively complete characterization of the extinct Fagopsis plant. The alternately arranged simple leaves have pinnate craspedodromous venation and prominent simple teeth. Staminate inflorescences are globose on a stout peduncle and contain anthers with tricolporate pollen. Pistillate inflorescences are ovoid heads with compact, helically arranged three‐flower units and are interpreted to have three styles per flower. The infructescence consists of small wedge‐shaped cupules, each containing three tiny fruits, and subtended by a persistent bract. The cupules unravel from the swollen peduncle at maturity and are often dispersed as strings of adhering fruit‐wedges which frequently take on a regular, more or less circular appearance. Fagopsis is unlike any living genus but has characters which support a relationship to the Fagaceae. Unlike extant members of the family, which typically have fruits adapted for animal dispersal, Fagopsis is less obviously specialized and perhaps adapted for wind dispersal. The striking differences in fruiting structures between Fagopsis and extant Fagaceae parallel the differences between the extant genera Platycarya and Juglans in the Juglandaceae, and Alnus and Corylus in the Betulaceae.