MANCHESTER, STEVEN R. Florida Museum of Natural History, Gainesville, FL 32611-7800 USA. - Leaves and fruits of Davidia (Cornales) from the Paleocene of North America.
Although now endemic to China, the genus Davidia (Nyssaceae) is
well represented in the Paleocene of mid-latitude North America. The
leaves, for more than a century called Viburnum antiquum
(Newberry) Hollick, conform to extant Davidia in the long
petioles and laminae with cordate base, pinnipalmate venation,
numerous pectinal veins, closely spaced percurrent tertiaries, and
large, simple, marginal teeth with medial vein insertion. Ovoid,
longitudinally ribbed, woody fruits co-occur with the leaves at six
localities in the Fort Union Formation of North Dakota, Montana,
Wyoming, and Colorado. Although usually preserved as impressions
without anatomical detail, silicified fruits from the Almont flora,
North Dakota, reveal internal structure diagnostic of Davidia.
The endocarps have six to eight single-seeded locules, each with an
elongate dorsal germination valve; vascular bundles pass through the
septae but do not form an axial strand. The fossil fruits are only
about half the size of the fruits of living Davidia
involucrata, but they are otherwise indistinguishable in the
morphological and anatomical characters studied. The confirmation of
Davidia as a common element of North American Paleocene floras,
along with the recently described extinct genus Amersinia, adds to
growing evidence that Cornales occupied a prominent position in the
Paleocene vegetation of North America accompanied by Platanaceae,
Cercidiphyllaceae, Betulaceae and Juglandaceae.
Key words: Cornales, Davidia, fruits, leaves, Nyssaceae, Paleocene