Llanvirn Trilobites from South Wales

Abstract

[Master of Philosophy thesis]. The Llanvirn trilobites of South Wales are described, together with faunas of probable Arenig and Llandeilo age from outcrops whose stratigraphical relationship to the Llanvirn is poorly understood. Twenty eight named species and subspecies are described and an additional thirty four forms are described under open nomenclature. Thirty seven genera are represented in total, and the following new species are erected: Merlinia contracta, Cyclopyge torquata, Degamella gladiata, Cnemidopyge pentirvinense and Cnemidopyge tenuis. Eoharpes primus? and Protostygina are recorded from Britain for the first time. Ontogenic stages of Barrandia homfrayi and complete material of Platycalymene tasgarensis simulata, Gastropolus obtusicaudatus and Cremastoglottos occipitalis is figured for the first time. This has enabled the cyclopyginine athinitsés of Gastropolus to be demonstrated, and has provided criteria for the separation of Bohemian Cremastoglottos from the type species. An historical review of previous stratigraphical and faunal studies is included, along with a summary of the Llanvirn in outcrop, and discussion on prevailing problems in biostratigraphy and series definition in the region. Important fossiliferous sections of early Arenig and Upper Llanvirn age are logged, potentially important sections demonstrating biozone or series transition are summarised and regional correlation and faunal distribution charts are provided.