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Paleodictyon
''Paleodictyon'' is a pattern, usually interpreted to be a burrow, which appears in the geologic record beginning in the Cambrian and in modern ocean environments.〔Swinbanks, D. D., 1982: ''Paleodictyon'': the traces of infaunal xenophyophores? Science, v. 218, 47-49.〕〔Ksiazkiewicz, M., 1970: Observations on the ichnofauna of the Polish Carpathians, in Crimes, T. P., and Harper, J. C., eds. Trace Fossils, Geological Journal, Special Issue 3, 283-322.〕〔Ekdale, A. A., 1980: Graphoglyptid burrows in modern deep-sea sediment: Science 207, 304-306.〕 Both irregular and regular nets are known throughout the stratigraphic range of ''Paleodictyon'', but it is the striking regular honeycomb pattern of some forms such as ''P. carpathecum'' and ''P. nodosum'' which make it notable and widely studied. Individual mesh elements may be millimeters to centimeters, and entire mesh patterns can cover areas up to a square meter. The edges or threads that make up the mesh are usually cylindrical or ellipsoid in cross-section, and some forms have vertical tubes connecting the mesh upwards to the sediment-water interface. Dolf Seilacher proposed in 1977 that it may be a trap for food, a mechanism for farming, or a foraging path.〔Seilacher, A., 1977: Pattern analysis of ''Paleodictyon'' and related trace fossils in Crimes, T. P., Harper, J. C., Trace Fossils 2: Geological Journal, Special Issue 9, 289-334.
〕 Alternatively, it has been suggested that it may be a cast of a xenophyophoran protist.〔
Much modeling work has been done on ''Paleodictyon''. Roy Plotnick, trace fossils researcher at University of Illinois at Chicago, modeled the form as resulting from the iterative modular growth of an unknown organism.〔Plotnick, R. 2003: Ecological and L-system based simulations of trace fossils. Palaeogeography Palaeoclimatology Palaeoecology 192, 45-58.〕 Garlick and Miller modeled it as a burrow with a relatively simple burrow algorithm.〔Garlick, G. D., and Miller, W., 1993: Simulations of burrowing strategies and construction of ''Paleodictyon'': Journal of Geological Education 41, 159-163.〕 Subsequent observations on ''Paleodictyon'' using Euler graph theory suggest that it cannot be an excavation trace fossil, and that it must therefore be an imprint, body fossil, or be of abiotic origin.〔Honeycutt, CE, and Plotnick, RE. 2005. Mathematical analysis of ''Paleodictyon'': a graph theory approach. Lethaia 38:345–350.〕
The IMAX film Volcanoes of the Deep Sea describes the search for a living animal that produces the ''Paleodictyon'', using the deep-water submersible DSV Alvin near volcanic vents that lie 3500 meters (12,000 feet) underwater in the Mid-Atlantic Ridge. They found and took samples from many of the Paleodictyon nodosum honeycomb burrows, however no creatures were found in any of them. They theorized that the burrows were being used for bacterial farming by whichever creature created them.
==References==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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