Benedict, John C. , Pigg, Kathleen B. , DeVore, Melanie L. .
Hamamelis-like fruits (Hamamelidaceae) from the Late Paleocene Almont flora of North Dakota, USA.
Infructescences of a Hamamelis-like fruit (Hamameloideae: Hamamelidaceae) are described from the Late Paleocene Almont flora of North Dakota, USA. The specimens show external morphology and are partially permineralized, with anatomical structure of fruits and the infructescence axis. Up to ten sessile, cuboidal to globose fruits are attached to an infructescence axis that measures up to 9.1 cm in length and 0.5 cm wide. Fruits are biloculate capsules 10-12 mm long x 10-12 mm wide, with a well preserved fibrous endocarp and partially preserved exocarp. The endocarp is comprised of an innermost carpel lining 1-2 cells thick of radially elongate palisade cells and an outer region 35-55 cells thick of tangentially elongate fibers. The exocarp, when well preserved, shows persistent styles on the outer fruit margins, bisecting the plane of dehiscence. Today, the family Hamamelidaceae is comprised of 3 subfamilies (tribes), one of which, the Hamameloideae, has fruits that bear only a single mature ovule per carpel and have explosive dehiscence. Although fruits in this subfamily are generally thought to be indistinguishable, genera show marked differences in infructescence type, relative size and shape of the capsule, persistence of style, and other morphological differences. The Almont fossils most closely resemble extant Hamamelis and Sinowilsonia , demonstrating that hamamelid fruits very similar to extant forms were well established in North America by the Late Paleocene.
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1 - Arizona State University, School of Life Sciences, Asu, Main Campus, Po Box 874501, Tempe, Arizona, 85287-4501, USA
2 - Georgia College & State University, Biological & Environmental Sciences, 135 Herty Hall, Campus Box 81, Milledgeville, Georgia, 31061, USA
Presentation Type: Oral Paper
Location: Salon G - Austin Grand Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 2:00 PM