Abstract Detail

Paleobotanical Section

Bergene, Julie [1], Taylor, Edith [1], Taylor, Thomas [1].

Anatomically preserved Dordrechtites from the Middle Triassic of Antarctica.

Dordrechtites is an enigmatic seed-bearing structure previously known only from South Africa and Australia. The discovery of compressed and permineralized specimens of this taxon at the base of Mt. Falla (upper Fremouw Formation) in the central Transantarctic Mountains extends the geographical distribution of the genus and increases the known floral diversity of the Triassic of Antarctica. It is also the first permineralized material of the taxon and thus provides additional characters that can help elucidate affinities of the structure by linking anatomical detail to surface compressions. The fossils appear to be preserved as compressions on the surface, but sections through the matrix reveal that they are permineralized within and can be studied by means of the peel technique. Dordrechtites specimens represent dispersed megasporophylls. Each is conspicuously T-shaped with a central, flattened area bearing the ovule, and two long slender extensions previously described as sterile arms or horns. The megasporophyll surface shows longitudinal striations. The central region is pyramidal in shape with an average length of 10 mm. The T-shaped sporophyll extensions are about 12 mm long by 1 mm wide and bend towards the central ovule-bearing region. Each structure bears one ovule with an adjacent presumed air pocket. Sporophyll tissue consists of large thick-walled sclerenchyma cells that are 40-70 μm wide. The integument consists of a bi-layered sclerotesta. The inner sclerotesta is densely packed with indistinct cells while the outer part is 5-20 cells deep; individual cells are 25-50 μm wide with oval to oblong rectangular cells that have thickened walls. A discontinuous layer consisting of radial files of cells occurs on the chalazal end of the ovule adjacent to the outer sclerotesta and may represent some type of abscission zone. The four previously described species, which are thought to be associated with Heidiphyllum, are very similar in size and shape to the Antarctic material, therefore the permineralized fossils can be directly compared to the compression forms.

Broader Impacts:

1 - University Of Kansas, Department Of Ecology And Evolutionary Biology, 1200 Sunnyside Avenue, Haworth Hall, Lawrence, KS, 66045-7600, USA

Keywords:
Antarctica
Dordrechtites
Triassic
Permineralization
Compression.

Presentation Type: Oral Paper:Papers for Sections
Session: 10
Location: Lindell C/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 10:45 AM
Number: 10002
Abstract ID:309