Ryberg, Patricia , Taylor, Edith .
Glossopterid ovulate diversity from Skaar Ridge, Transantarctic Mountains, Antarctica.
Skaar Ridge in the Transantarctic Mountains of Antarctica is one of two localities where anatomical preservation of the Permian Glossopteridales has been found. To date three genera of ovules have been described, Plectilospermum elliotii Taylor and Taylor, Choanostoma verruculosum Klavins et al., and Lakkosia kerasata Ryberg. This research presents a new megasporophyll genus with attached ovules. Ovoid ovules are attached to the adaxial surface of a sporophyll with glossopterid anastomosing venation. Ovules are small (1.1 mm x 0.97 mm) with little external ornamentation. The sarcotesta consists of a single cell layer with thickened exterior and anticlinal walls. The sclerotesta is up to 10 cells thick with heavily sclerified cells. Endotesta cells are highly elongate and appear as a lining along the interior of the sclerotesta. The nucellus is free from the integument and megagametophyte tissue is preserved. The micropyle seals with the enlargement of sclerotesta cells. Comparison of this new genus with previously described genera reveals diverse features of Skaar Ridge ovules. Ovule size ranges from 4.8 mm (Plectilospermum) to 1.1 mm (new genus) in length. Ornamentation of the micropyle is found in both Choanostoma and Lakkosia, but different layers of the testa form these specialized features. Ornamental features of the genera may have helped in pollination and dispersal of the seeds. The micropylar features of Choanostoma and Lakkosia may have allowed pollen to settle on the micropyle as well as transporting ovules along water currents. Sarcotestal wings, present in Plectilospermsum and Lakkosia, may have allowed for localized dispersal. The presence of five genera of ovules reveals a high level of local diversity within the glossopterids.
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1 - University Of Kansas, Department Of Ecology & Evolutionary Biology, 1200 Sunnyside Ave., Lawrence, KS, 66045, USA
2 - University Of Kansas, Department Of Ecology And Evolutionary Biology, 1200 Sunnyside Avenue, Haworth Hall, Lawrence, KS, 66045-7600, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Union A/Hyatt
Date: Tuesday, July 10th, 2012
Time: 1:45 PM