Paleocene floras of Wyoming, Montana, Colorado and North Dakota are typically dominated by hamamelid families (Platanaceae, Betulaceae, Juglandaceae), and Cupressaceae (incl. Taxodiaceae) but genera of the Cornaceae sl. are also well-represented, and relatively little studied. These fossil remains, including leaf impressions and permineralized fruits, provide early records for the genera Cornus, Nyssa, and Langtonia and include two species of a newly recognized extinct genus with affinities to Camptotheca and Davidia. The new genus, not yet named, is known from abundant leaves, formerly attributed to Viburnum cupanioides and V. antiquum, and consistently associated infructescences, fruits and associated leaves. The same leaf and fruit association has been found in the Paleocene of Kamchatka and northeastern China. The leaves are readily distinguished by their long petioles from Viburnum, and have serrated, cordate based leaves similar to those of extant Davidia. The infructescences consist a stout stalk topped by a cycle of about five bract scars and a head of trilocular fruits. The fruits, which are commonly found dispersed as well, are usually trilocular and have an epigynous calyx. One species has obtrullate fruits with fused sepals; the other has elongate-ellipsoidal fruits with free calyx tips. Permineralized specimens reveal that the fruits lack a central vascular strand and have single seeded locules with apical germination valves--features consistent with assignment to the Cornaceae sensu Eyde. These fossil remains indicate that at least three main groups of the Cornaceae (nyssoids, mastixioids and Cornus itself) were diverse by the early Tertiary.

Key words: Camptotheca, Cornaceae, Cornus, Davidia, Nyssa, Paleocene