Fossilization and an approach to phylogeny

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1. Total amounts of organic carbon produced by organisms through geologic time are estimated at 1.4-8.1 X <10^(25)> g. Total species which appeared on the earth throughout geologic time are also estimated at 0.9-5.7 X <10^8> . Both values suggest an order of <10^3> times more than the organic carbon preserved in whole sedimentary rocks and also the fossil species which have hitherto reported.2. Controlling factors of fossilization are (1) accumulation, (2) fossilization in a narrow sense, and (3) preservation. The most important factor is how large the population is, which is included in the accumulation factor. In this co-operative research, however, has been focused on fossilization in a narrow sense.3. Hydroxyapatite [ <Ca_5> ( <PO_4> <)_3> OH] is the main component of vertebrate hard tissues. This mineral has a low solubility of 0.01 mg/l in neutral water, which is the reason why the vertebrate fossil of hydroxyapatite are apt to be preserved as fossils. A Late Pleistocene fossil tusk collected from the sea bottom off Hinomisaki, Shimane Pref. contains well preserved collagen molecules. Diagenetic alteration and variation are discussed from the viewpoints of microscopic, histochemical, biochemical and mineralogical observation.4. Calcite ( <CaCO_3> ) is the representative mineral species in carbonate fossils. This mineral has a high solubility of 1g/1 in <CO_2> -saturated water. For this reason carbonate fossils are easily replaced or impregnated by other minerals. Replacement by siderite usually occurs in fresh-water sediments. Fossilization processes on molluscan and coral fossils were discussed.