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Paleobotanical Section

Klavins, Sharon D. [1], Taylor, Edith L. [1], Taylor, Thomas N. [1].

Anatomically preserved ovules from the Middle Triassic of Antarctica.

The Fremouw Formation of the central Transantarctic Mountains is remarkable for the diversity of structurally preserved plants of Middle Triassic (Anisian) age. The Fremouw flora thus far includes five families of gymnosperms for which reproductive structures are known. This has contributed significantly to our understanding of both the diversity and reproductive biology of early Mesozoic seed plants. Here we present two anatomically preserved ovules from the Fremouw flora that may represent a new group of gymnosperms. The ovules are large (up to 1 cm in length and width), bilaterally symmetrical, and possess a three layered integument. They differ from all Triassic ovules known to date in possessing a sclerotesta that shows elaboration at the base and apex and forms rigid extensions either around the pedicel or at the lateral margins. A robust vascular strand with scalariform tracheids expands into a disk at the base of the nucellus, with two vascular strands that extend ca. one-third of the length of the ovule internal to the lateral margins of the sclerotesta. To date, anatomically preserved ovules have been described for the Corystospermales, Petriellales, and Taxodiaceae, as represented in the Fremouw flora; ovules remain unknown for the Fremouw cycads and podocarps. The suite of characters observed in these new ovules does not appear to correspond to what is known for any of these groups. In part due to the dearth of anatomical information on ovules of other early Mesozoic gymnosperms, there is insufficient evidence to assign them to a known taxonomic group. Their unusual structure, however, suggests additional gymnosperm diversity in the Fremouw flora.


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Related Links:
Paleobotany at the University of Kansas


1 - University of Kansas, Department of Ecology & Evolutionary Biology, Natural History Museum and Biodiversity Research Center, 1200 Sunnyside Avenue, Lawrence, Kansas, 66045-7534, USA

Keywords:
gymnosperms
anatomy
Triassic
Antarctica
ovules.

Presentation Type: Oral Paper
Session: 22-4
Location: 404/Hilton
Date: Monday, August 15th, 2005
Time: 4:15 PM
Abstract ID:265


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