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Megascopic Algae 1300 Million Years Old from the Belt Supergroup, Montana: A Reinterpretation of Walcott's Helminthoidichnites

M. R. Walter, John H. Oehler and Dorothy Z. Oehler
Journal of Paleontology
Vol. 50, No. 5 (Sep., 1976), pp. 872-881
Stable URL: http://www.jstor.org/stable/1303584
Page Count: 10
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Megascopic Algae 1300 Million Years Old from the Belt Supergroup, Montana: A Reinterpretation of Walcott's Helminthoidichnites
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Abstract

In 1899, C. D. Walcott described carbonaceous films on bedding surfaces of dark grey shale from the 1300 m.y. old Greyson Shale of the Belt Supergroup in Montana as trace fossils, assigning them to the genus Helminthoidichnites Fitch. We have reexamined Walcott's collection and have concluded that the fossils represent megascopic and probably eukaryotic algae. They are redescribed here under the names Proterotainia montana, n. gen., n. sp., P. neihartensis (Walcott) n. comb., Lanceoforma striata, n. gen., n. sp., and Grypania spiralis (Walcott), n. gen., n. comb. These are the oldest megascopic body fossils now known, and they extend the known record of megascopic algae by at least 400 m.y. The relatively high diversity and quality of preservation of these fossils demonstrate that fine-grained, clastic sediments are potential repositories of well-preserved Precambrian plants.

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