Abstract

Twenty-seven graptolite species are reported from the lowermost Silurian (Rhuddanian) ascensus-acuminatus and vesiculosus biozones of Montagne Noire in southwestern France. Four species are left in open nomenclature, four are new: Normalograptus crassus, Neodiplograptus lautus, Dimorphograptus compactus and Huttagraptus solidus. The joint occurrence of Akidograptus ascensus, Parakidograptus acuminatus and Cystograptus ancestralis, recorded in the Gabian-1 section, suggests correlation of the whole succession at this site with the middle part of a combined ascensus-acuminatus Biozone. Revision of museum collections revealed that other elements that are characteristic of the ascensus-acuminatus Biozone assemblage in peri-Gondwanan Europe, such as Normalograptus trifilis, N. longifilis and Neodiplograptus lanceolatus, have been recovered from several other localities in Montagne Noire that are no longer accessible. The graptolite assemblage of the Gabian-2 section, with common Cystograptus vesiculosus, Dimorphograptus extenuatus, D. elongatus and Atavograptus atavus, belongs to the lower part of the vesiculosus Biozone, whilst the appearance of D. swanstoni and D.? physophora in the upper part of the section represents a higher, although not the uppermost, part of the biozone. This is the first record of a diverse dimorphograptid fauna within the vesiculosus Biozone in the Gondwanan part of Europe.

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