Athena Review Image Archive ™
Thallophyca corrugata, detail of algae cells
Detail of algae cells of Thallophyca corrugata (after Li et al.1998, fig.3)
In
China's central Guizhou province, near Weng’an, the late
Proterozoic Nantuo Formation (620 to 590 mya) is overlain by the early
Vendian Doushantuo Formation (590-565 mya). Preservation of phosphate
layers in the Doushantuo Formation is excellent, with soft
tissues sometimes preserved to the cellular level (Li et al 1998).
The
Duoshantuo biota, dating from the end of the Precambrian period,
includes a diverse, well-preserved floral assemblage, including
multicellular thallophytes, acritarchs, and cyanophytes. The
best-preserved specimens include thallus tissues that resemble those of
modern seaweed. Also present are marine fauna that closely resemble sea
pens (Cnidarians) or sponges (Xiao et al. 1998, 2000).
The figure shows detail of cells in the fossilized thallus tissue of Thallophyca corrugata, a marine algae or seaweed from the Duoshantuo Formation. The cells are labelled for nucleus (N) and chloroplasts (C).
Thallus tissues from the Duoshantuo algae lack specialized cell structures but have differing structural forms in the same individual species. A present-day analogy is provided by kelp, a well known brown algae of the order Laminariales. While kelp has various parts that in some ways resemble those of land plants, their thallus tissue lacks the specialized, distinctive vascular structures of roots, branches, or leaves found in land plants. In spite of having these various structures, all thallus cells from all parts of kelp and other seaweed have chloroplasts and perform photosynthesis, whereas only leaf cells do so in land plants.
References:
Li, C-W, J-Y Chen, and T-E Hua 1998. Precambrian Sponges with Cellular Structures. Science 279, pp. 879 - 882.
Xiao,
S., Y. Zhang, and A.H. Knoll 1998. Three-Dimensional
Preservation of Algae and Animal Embryos in a Neoproterozoic
Phosphorite. Nature 391, pp. 553-558.
Xiao, S., X.Yuan, and A.H. Knoll 2000. Eumetazoan Fossils in Terminal Proterozoic Phosphorites? Proceedings of the National Academy of Sciences of the United States, 97 (25), pp. 13684-13689.
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