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New Silurian nautiloids Phragmoceras Broderip, 1839, and Tubiferoceras Hedström, 1917, from the Prague Basin (Bohemia)

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Author(s): Manda Š

Journal: Bulletin of Geosciences
ISSN 1214-1119

Volume: 82;
Issue: 2;
Start page: 119;
Date: 2007;
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Keywords: Nautiloidea | Discosorida | new taxa | palaeobiogeography | Silurian | Prague Basin

ABSTRACT
The morphologically distinct nautiloid genera Phragmoceras and Tubiferoceras (Discosorida, Phragmoceratidae) with an endogastric brevicone shell and a contracted aperture are characteristic components of the Silurian tropical faunas of Baltica and Laurentia. Seven previously known species of Phragmoceras from the Prague Basin (Perunica) are mainly from cephalopod limestones of the Ludlow age. Amongst these, two species are recorded from beyond the Prague Basin. Phragmoceras imbricatum is recognised in Avalonia and Baltica and its geographic distribution suggests a palaeobiogeographical connection across the Rheic Ocean during the earlier Ludlow time. Phragmoceras labiosum was recorded in the Bohemian-type Ludfordian fauna of Sardinia (peri-Gondwana). This paper deals with several phragmocerids from the Prague Basin which have not been recorded before. They include Phragmoceras munthei from the latest Llandovery and earlier Wenlock, Tubiferoceras proboscoideum from the early Wenlock, Phragmoceras acuminatum, Phragmoceras sigmoideum, Phragmoceras cf. undulatum, and Phragmoceras cf. ventricosum from the late Wenlock. A new species Phragmoceras koneprusensis sp. nov. from the early Ludfordian (Ludlow) is established. These species are closely related or conspecific to those described from Gotland (Baltica), Ireland (Laurentia) or Wales (Avalonia) and indicate an open seaway between the Prague Basin (Perunica) and Baltica, Laurentia and Avalonia, respectively, since the latest Llandovery. In addition, occurrences of phragmocerids in the Prague Basin suggest that in contrast to the rest of peri-Gondwanan areas a relative temperate water environment was typical for Perunica since latest Llandovery.

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