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Sporulation and ultrastructure in a late Proterozoic cyanophyte - Some implications for taxonomy and plant phylogenyElectron microscopical studies of a morphologically diverse, coccoid, presumably late Proterozoic blue-green alga are here reported. They show, together with light microscopy, that the form studied is widespread in the Cordilleran geosyncline, extend the record of well-defined endosporangia perhaps 700 million years into the past, and reveal previously unrecorded ultrastructural details. Coming from northeastern Utah, southwestern Alberta, and east central Alaska, these minute fossils belong to the recently described, morphologically diverse taxon Sphaerocongregus variabilis Moorman, are related to living entophysalidaceans, and have affinities with both the chroococcalean and chamaesiphonalean cyanophytes. Included in the morphological modes displayed by this alga are individual unicells, coenobial clusters of unicells, and a range of endosporangia comparable to those described for living entophysalidaceans. Scanning and transmission electron microscopy reveal that the endospores are commonly embedded in a vesicular matrix, that some of them show what appears to be a bilaminate or perhaps locally multilaminate wall structure, and that some remain together to mature as coenobial clones or 'colonies'. Taxonomic classification and phylogeny are discussed.
Document ID
19760048683
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Cloud, P. (California Univ. Santa Barbara, CA, United States)
Moorman, M. (California Univ. Santa Barbara, CA, United States)
Pierce, D. (California, University Santa Barbara, Calif., United States)
Date Acquired
August 8, 2013
Publication Date
June 1, 1975
Publication Information
Publication: Quarterly Review of Biology
Volume: 50
Subject Category
LIFE SCIENCES (GENERAL)
Funding Number(s)
CONTRACT_GRANT: NGR-05-010-035
CONTRACT_GRANT: NSF GB-23809
Distribution Limits
Public
Copyright
Other