Taxodium wallisii sp. nov.:: First occurrence of Taxodium from the Upper Cretaceous

Exceptionally well-preserved silicified remains of a new species of Taxodium have been recovered from the Late Cretaceous (ca. 70 million years old) sediments of the Horseshoe Canyon Formation near Drumheller, Alberta, Canada. Specimens include three-dimensionally preserved branches bearing dimorphic leaves, pollen cones, pollen, seed cones, and seeds. The abundance and quality of preservation of these remains have allowed for detailed examination of morphological and anatomical features for comparison with extant representatives of the Taxodiaceae. The vegetative axes bear taxodioid leaves and rare cupressoid leaves; staminate and pistilate axes are subtended entirely by cupressoid leaves. The seed cones are erect, short-stalked, and globose, arranged alternately on branches, and bear up to fifteen helically arranged, deciduous bract-scale complexes. Each cone scale bears two more or less triangular seeds. Vasculature and arrangement of the resin canals of the cone scales are much more complex than that of any of the extant species examined. The pollen cones are typical of extant Taxodium; the pollen grains are structurally comparable, but small when compared with extant representatives of the genus. Comparison of these fossils with extant representatives of the Taxodiaceae indicate that they are most similar to Taxodium, but are comparable to Glyptostrobus and Cryptomeria in some features. The Horseshoe Canyon Taxodium is the first unequivocal report of Cretaceous Taxodium from North America and provides insight into the early evolution of the genus and phylogenetic relationships among other representatives of the family.