Axsmith, Brian , Fraser, Nicholas , Zan, Shuqin .
A remarkable Late Triassic plant assemblage from northern China.
Previous reports of plant macrofossils from the Upper Triassic Yancaogou Formation in Liaoning Province PRC indicated a diverse flora including Annulariopsis, Cycadocarpidium, Dictyophyllum, Glossophyllum, Neocalamites, Pterophyllum and several other taxa. More recently, detailed descriptions of the cones Leptostrobus and Sorosaccus have appeared. However, there is little indication of the degree of completeness and articulation of many of the plants in these publications. Our recent excavations show that this assemblage contains some of the most intact plant fossils known from anywhere in the Triassic. For example, Neocalamites up to 3 m tall, intact crowns of the cycad Ctenis, and large fronds of the fern Cladophlebis attached to rhizomes have been recovered. New conifer records include intact seed cones of Schizolepis and Swedenborgia, and a forked axis with ten attached pollen cones. However, the most significant and unexpected finds so far are of corystospermalean ovulate strobili attributable to Umkomasia. The new Umkomasia is similar to U. franconica from the Jurassic of Germany, which is the only other known laurasian species, but the cupules are smaller and more elongate. It is also similar to the type species U. macleanii. Leaves associated with the Chinese Umkomasia are tentatively referred to Thinnfeldia, and may have been produced by the same plant. Associated seeds with elongate, curved micropyles are similar to those of gondwanan species of Umkomasia. These fossils are significant in representing the first report of corystospermalean reproductive structures from Asia, and only the second report of Umkomasia from the entire northern hemisphere. The new Chinese Umkomasia find also supports leaf-based evidence that the Corystospermales were present in Laurasia as early as the Late Triassic.
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1 - University of South Alabama, Biological Sciences, Life Sciences Building 124, Mobile, AL, 36688, United States
2 - National Museums Scotland, Chambers Street, Edinburgh, EH1 1JF, Scotland
3 - The Geological Museum of China, Beijing, 100034, PR China
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 9:00 AM