Hu, Shusheng , Dilcher, David , Schneider, Harald , Jarzen, David .
Eusporangiate fern sporangia from mid-Cretaceous Dakota Formation exposed in Minnesota.
The mid-Cretaceous Dakota Formation outcrops in south central Minnesota often consist of clay sediments rich in plant fossils. A palynological study of the Dakota Formation sediments from southern Minnesota has yielded some fern sporangia that appear similar to those of extant eusporangiate ferns (e.g. Ophioglossaceae, Marattiaceae). This is the first record of eusporangiate ferns in the Dakota Formation. In contrast a good fossil record for the Marattiaceae exists from the Carboniferous to the Jurassic. There is currently a gap in the fossil record between the Jurassic and Recent. Eusporangiate sporangia recovered from the Dakota Formation of the Coutland clay pit in south central Minnesota provide evidence for the existence of marattioid ferns during the mid-Cretaceous in North America. Two types of sporangia are described. One type is elongate, elliptical and slightly asymmetrical, 1.2 X3.5 mm, ca 4500 spores in it. The other type has an irregular shape often consisting of three lobes. Their sizes range from 0.6 X 0.6 mm to 1.2 X 2 mm. Each individual sporangium may contain about 3800 spores, whereas the smallest of the sporangia may contain about 900 spores. The characteristics from sporangia morphology, spore wall ultrastructure, spore morphology and spore output per sporangium indicate that these sporangia and spores have a Marattiaceae affinity. This is a significant record of the Marattiaceae in post Jurassic times.
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1 - University of Florida, Department of Geological Sciences, Florida Museum of Natural History, Gainesville, Florida, 32611, USA
2 - University of Florida, Florida Museum of Natural History, Po Box 117800, Gainesville, Florida, 32611-7800, USA
3 - University of Goettingen, Department of Systematic Botany, Albrecht von Haller Institute for Plant Sciences, Untere Karspuele 2, Goettingen, D-37073, Germany
Presentation Type: Poster
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM