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Mat-forming coccoid cyanobacteria from Early Silurian marine deposits of Sudetes, Poland

100%

Kremer B.

Acta Palaeontologica Polonica

2006

tom 51

nr 1

Mass occurrence of mats comprised of benthic coccoid cyanobacteria is reported from early Silurian black radiolarian cherts exposed at Żdanow village (Bardzkie Mountains, Sudetes, southwestern Poland). The cherts contain laminated organic matter representing degraded benthic coccoid cyanobacterial mats. The remains of cyanobacteria occur as laminated agglomerations of variously preserved subglobular colonies composed of spherical cells of variable size and numbers. The morphology of remnants of cells and their mucilaginous envelopes, structure of colonies, and particularly the presence of small granular structures resembling reproductive cells known in extant coccoid cyanobacteria as baeocytes, permit to compare the Silurian microbiota with modern cyanobacteria assigned to the genera Stanieria or Chroococcidiopsis.

A new genus of Late Ordovician-Early Silurian pentameride brachiopods and its phylogenetic relationships

100%

Jin J., Popov L. E.

Acta Palaeontologica Polonica

2008

tom 53

nr 2

Protanastrophia repanda gen. et sp. nov. is a reef−dwelling parastrophinid brachiopod in the Lower Silurian (uppermost Telychian) Attawapiskat Formation of the Hudson Bay region of Canada. It is characterized by a small, quasi−smooth shell with gentle anterior costae, a tendency towards an asymmetrical, sigmoidal anterior commissure, and widely separate, subparallel inner hinge plates. Protanastrophia first appeared in the marginal seas of Siberia (Altai, Mongolia) during the Late Ordovician, retaining the primitive character of discrete inner hinge plates in the superfamily Camerelloidea, and preferred a carbonate mound depositional environment. It survived the Late Ordovician mass extinction and subsequently spread to Baltica and Laurentia during Early Silurian (Llandovery) time. Superficially similar asymmetrical shells of Parastrophina portentosa occur in the Upper Ordovician carbonate mound facies of Kazakhstan but differ internally from the new genus in having a septum−supported septalium. Phylogenetic analysis indicates that, within the Camerelloidea, asymmetrical shells with a sigmoidal anterior commissure evolved in Protanastrophia repanda and Parastrophina portentosa independently during the Late Ordovician as a case of homoplasy. The two species belong to separate parastrophinid lineages that evolved in widely separate palaeogeographic regions.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Jin J.

1 Kremer B.

1 Popov L. E.

1 2008

1 2006

Wyniki wyszukiwania

Mat-forming coccoid cyanobacteria from Early Silurian marine deposits of Sudetes, Poland

A new genus of Late Ordovician-Early Silurian pentameride brachiopods and its phylogenetic relationships