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The overarching purpose of our research is to understand the evolution of land plants from their algal ancestors. In recent decades, this problem has been addressed from a phylogenetic stand-point and, more recently, from the view of genomics and molecular phylogeny. Such studies are of necessity dependant upon existing plants and algae as the primary, if not the only, source of information, and we are still left with a huge evolutionary gap remaining between the nearest living relatives of the land plants and the basal (bryophyte) groups. That gap can be seen both in terms of overall morphology and in phylogenetic terms of assessed character states because so many novel structures characterize the embryophytes (land plants) as different from the algae. The project, therefore, is designed to overcome this evolutionary gap between the land plants and their algal ancestors by searching for fossils and microfossils that might yield specific clues as to the nature of the evolutionary processes that led to the origin of a land flora.

We have continued to collect and extract microfossils from Upper Cambrian and Lower Ordovician samples in the eastern US (Tennessee) and in the western US (Utah and Wyoming). This year we brought two undergraduate students from the Geology & Geophysics Department at Boston College into the field with us during a nearly month-long field season in the western US. The most exciting part of the research his year has been the discovery and initial interpretation of sheets of spore-like cells from the Kanosh Shale in western Utah. This lower Middle Ordovician deposit sits at a critical time interval between the widely accepted origin of land plants and the more controversial Middle Cambrian origin that supported by this research. In addition to spore masses, we have found what appear to be entire thalli (plant bodies) from this unit. These are new to paleontology and we will be preparing and analyzing these fossils now and throughout the third year of the project. Figure 1 shows examples of these thalli and associated spore-masses. These fossils have the potential to contribute significantly to some very long-standing debates in plant evolution, in addition to supplying some new ideas. They appear to be composed of sheets of spore-like cells, but they are organized in regular patterns that appear to reflect vegetative divisions to produce a plant body. This very form, however, was predicted as a necessary intermediate step in the origin of land plants through a theory proposed in 1908 by F. O. Bower (the antithetic theory for the origin of the sporophyte generation). Bower specifically predicted that the first step in the de novo evolutionary origin of a sporophyte generation would be a plant thallus in which all the cells acted as spores - that appears to be exactly what we are seeing in these fossil forms. In any case, we are very excited about this discovery, which now adds to work in progress on even earlier fragments from last year's efforts.

Figure 1. Spore-mass and circular thalli  from the Kanosh Shale, Fossil Mountain, western Utah. A. The light microscope image spore-bodies that appear to have been formed through regular cell division in a single plane to produce a rounded shape. B. Larger compressed thalli preserved directly on the bedding plane. These specimens, which were found during this summer's field work, are presently being studied in more detail.