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Abstract Detail


Paleobotanical Section

Benedict, John C. [1], Taylor, Witt [1], Pigg, Kathleen B. [1], DeVore, Melanie L. [2].

Late Paleocene seeds from Beicegel Creek (McKenzie County, North Dakota, USA) with affinities to the genus Spirematospermum Chandler (Zingiberales).

More than 100 isolated seeds, embryos and embryo casts are described from the Late Paleocene Beicegel Creek locality in western North Dakota. Embryo casts of this type were figured from the Almont flora as "clavate structures" by Crane, Manchester and Dilcher in 1990. Specimens are preserved within a silicified shale, and show remarkable anatomical detail obtained from cellulose acetate peels. The seeds are opercular, 6-7 mm long x 2-3 mm wide, and elliptical with a slightly inflated chalazal end. Seeds are circular in transverse section, and the seed coat is composed of two distinct layers. The outer layer is uniseriate and sclerified, appearing spirally striate in surface view, and as a distinct palisade layer in transverse section. The inner layer is 3-5 cells thick, sclerified, and tangentially elongate. Embryo casts are straight and are surrounded by a narrow cavity that may have been filled with endosperm. A septum delimits the embryo sac from the chalazal chamber, which contains the parenchymatous tissue of the endosperm. The distinctive spirally striate seed coat, septum, chalazal chamber, and endosperm are all indicative of the genus Spirematospermum Chandler. No aril has been observed, however this may be because of a lack of preservation. Spirematospermum is a well known fossil zingiberalean taxon that occurs from the Late Cretaceous to the Pliocene in Europe. The North Dakota specimens are similar to S. wetzleri from the Miocene Fasterholt flora of Denmark, but differ in seed coat anatomy. This occurrence of Spirematospermum, along with related genera from the Late Cretaceous of Mexico and the Eocene of Oregon, demonstrates that the Zingiberales were more significant components of the North American flora than previously recognized.


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1 - Arizona State University, School of Life Sciences, P.O. 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

Keywords:
Zingiberales
Spirematospermum
fossil seed
Paleocene
Almont
Beicegel Creek flora
monocot embryo.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P54003
Abstract ID:2146


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