Rhamnites cleburnii (LESQUEREUX) MCIVER et BASINGER

Manchester, Steven R., 2014, Revisions To Roland Brown’S North American Paleocene Flora, Acta Musei Nationalis Pragae Series B 70 (3 - 4), pp. 153-210 : 175

Rhamnites cleburnii (LESQUEREUX) MCIVER et BASINGER

Brown (1962) indicated that Rhamnus cleburnii and R. goldiana (types both from the same locality) are very similar except that the former has a cuneate base and the latter is cordate. The cordate-based leaves have a series of strong agrophic veins. McIver and Basinger (1993) designated R. cleburnii as the type species of the fossil genus, Rhamnites , and established the new combination Rhamnites cleburnii . The closely spaced percurrent tertiaries are consistent with Berchemia , Karwinskia , Rhamnidium , Rhamnus , and some other genera of Rhamnaceae . The leaves are always entire-margined, contrasting with the serrate condition in many extant species of Rhamnus . From the same locality, an entire-margined leaf that Brown (1962, Pl. 39, fig. 2) figured as Magnolia regalis HEER , has closely spaced oppositepercurrent tertiary veins unlike Magnolia and appears to represent Rhamnites cleburnii . Leaves with similar architecture including the scalariform type of intercostal venation, occur in Dipterocarpaceae (e.g., Hopea , Parashorea , Shorea ), and Dilleniaceae (e.g. Tetracera ). Wolfe (1977) attributed leaves from the Paleogene of Alaska, to Dipterocarpaceae , but the distinctive winged fruits of that family have not been recovered from Alaska or any other North American paleobotanical sites.