XVI International Botanical Congess

Large numbers of fossil aquatic plants from the St. Mary River Formation (Maastrichtian) were discovered near Cardston, Alberta. Fossils are preserved as compression/impressions in siltstones and sandstones that were rapidly deposited in a shallow pond during an overbank flood. At least 16 taxa of herbaceous monocots, dicots and ferns were preserved in situ and have allowed whole plant reconstructions of several taxa. The flora is dominated by Quereuxia angulata (Newb.) Baik., Hydropteris pinnata Rothwell & Stockey and Fortuna marsilioides (Bell) McIver & Basinger. In addition, to these taxa, an undescribed herbaceous dicot with a long clasping petiole, crenate margins, reticulate actinodromous venation and chloranthoid to rosoid teeth has been described. A previously undescribed large rosette-forming Quereuxia-like plant has also been identified. Fragments of at least one taxodiaceous conifer are being reconstructed for use in phylogenetic analysis. A number of broad-leaved monocots, including Hamaenthophyllum Budantsev are present. These fossils are rarely preserved in most floras and promise to add much to our knowledge of Cretaceous whole plant reconstructions.