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Abstract Detail


Systematics Section

Benedict, John C.  [1], Pigg, Kathleen B. [2], DeVore, Melanie L. [3].

Fossil flowers of Prunus and Oemleria (Rosaceae: Prunoideae) from the latest early Eocene Republic flora of northeastern Washington state, USA.

The first documented occurrences of fossil flowers of Prunus and Oemleria (Roseaceae: Prunoideae) are described from the latest early Eocene Republic flora of northeastern Washington. Based on eight specimens, the Prunus flowers are actinomorphic, unicarpellate and perfect with a gynoecium consisting of a distally flared, bilobed stigma, an elongate style, and a bilaterally asymmetric ellipsoid ovary. They are perigynous, and pentamerous with a campanulate hypanthium bearing a calyx with five distinct, apically acute sepals attached to the hypanthium. At least ten dorsifixed stamens are arranged in two whorls, an inner one in which stamens are reflexed inward and an outer whorl of extended stamens. Pollen from the outer whorl is 24 µm long and 15 µm wide, tricolpate to tricolporate with a striate exine; clusters of smaller, presumably immature grains lacking distinctive ornamentation were recovered from the inner whorl. Two young, developing fruits are recognized that, in contrast to the flowers, have fewer perianth remnants and larger, symmetrical ovaries. The smaller of these (4 mm long x 2.3 mm wide) has remnants of a senescent style and the larger one (9 mm long x 3.7 mm wide) lacks a style. The single specimen of Oemleria is 26 mm long, actinomorphic, perigynous and has five free pistils that are partially enclosed by an incomplete hypanthium. Each pistil is 8 mm long, with the characteristic prunoid features of a flattened, bilobed stigma, an elongate style up to 3 mm long, and a bilaterally asymmetric, ellipsoid ovary 5 mm long x 3 mm wide. The lack of a corolla and stamens suggests the Oemleria flower is at a post-anthesis stage. These flowers are found in association with relatively common rosaceous leaves, including several distinct types assignable to Prunus, some bearing petiolar glands. Together, these and additional fossils from Republic document the first major radiation of the Rosaceae.

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1 - Arizona State University, School of Life Sciences, PO Box 874601, Tempe, AZ, 85287-4601, USA
2 - Arizona State University, School of Life Sciences, P.O. Box 874501, Tempe, Arizona, 85287-4501, USA
3 - Georgia College & State University, Biological & Environmental Sciences, 135 Herty Hall, Campus Box 81, Milledgeville, Georgia, 31061, USA

Keywords:
Rosaceae
fossil flower
Eocene
Republic flora
Prunus
Oemleria.

Presentation Type: Oral Paper:Papers for Sections
Session: 10
Location: Ballroom D/Convention Center
Date: Monday, August 2nd, 2010
Time: 2:00 PM
Number: 10005
Abstract ID:713


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