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Paleobotanical Section

Pigg, Kathleen B. [2], Wojciechowski, Martin F. [2], DeVore, Melanie L. [1].

Samaras from the Late Paleocene Almont and Beicegel Creek floras of North Dakota, U.S.A., with potential affinities to Securidaca (Polygalaceae).

A distinctive fruit previously referred to as a "non-schizocarpic samara" is described from the Late Paleocene (Tiffanian) Almont and Beicegel Creek floras of North Dakota, U.S.A. on the basis of 33 specimens, including newly collected material.Samaras are 3.5 cm long x 0.9 cm wide with an oval main fruit body 0.7-0.9 cm long x 0.5-0.6 cm wide and 2.5-3.0 mm thick that is attached to an elongate wing that superficially resembles that of a maple samara.The wing has fine subparallel venation originating from the main fruit body and arching distally with occasional dichotomies and reticulations.Unlike Acer, the fruit is apparently solitary with a "beak" extending into an elongate pedicel several centimeters long.An elongate flap of tissue arches above the main fruit body. Transverse sections of the fruit body show a single developed seed with a prominent palisade layer.The North Dakota samaras are similar to Deviacer, a genus established by Manchester for similar fruits previously referred to by Wolfe and Tanai as "Acer arcticum" that occur in several western North American Paleocene and Eocene floras and in the Eocene of northeastern China.In contrast to earlier suggestions that the fruits were sapindaceous, the position of the wing, the elongate pedicel and the flap-like extension of the proximal fruit wall clearly resemble the present day Securidaca (Polygalaceae). These fruits also resemble certain dalbergioid legume fruits with asymmetric samaras described by Mirle and Burnham.Evidence from recent molecular studies indicate that Polygalaceae is nested along with Fabaceae, Surianaceae, and Quillaja within the Fabales (sensu APG II).Previously the earliest fossil evidence for the Polygalaceae was from Eocene pollen of Colorado. Together with the earliest record of Fabaceae from the Late Paleocene of Wyoming, these samaras provide independent evidence for an earlier divergence of these two families.


1 - Georgia College & State University, Biological & Environmental Sciences, 135 Herty Hall, Campus Box 81, Milledgeville, Georgia, 31061, USA
2 - Arizona State University, School of Life Sciences, PO Box 874501, Tempe, Arizona, 85287-4501, USA

Keywords:
Securidaca
Polygalaceae
Paleocene
samara
fossil.

Presentation Type: Paper
Session: 5-12
Location: Maybird (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 11:30 AM
Abstract ID:594


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