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Earliest Carboniferous goniatite recovery after the Hangenberg Event
Following the extinction of most goniatites and clymeniids below the new Devonian/Carboniferous boundary, only prionoceratids survived to give rise to new groups. Comments are made on the faunas known around the boundary in Europe and North America. Juvenile goniatite faunas are known in the earliest Carboniferous in many parts of the world. In the Stockum Limetone faunas these include evolute early stages with or without constrictions which have recently, but not convincingly, been referred to Acutimitoceras. Also there are costate early stages and forms with sulcate margins referred to Sulcimitoceras. The relation of these early stages to more normal adult stages is a fascinating puzzle awaiting solution. Illustrations and brief descriptions of these forms are given. Early stages also occur at similar levels in the Montagne Noire, Ireland, Missouri and in the Exshaw Shale of Canada and these occurrences are reviewed. Attention is drawn to how evolutionary novelty, following the extinctions at the Hangenberg Event, shows first as variety in early stages and the initiation of new stocks of Prionoceratidae and then of quite new groups, including the Voehringeritinae, Karagandoceratidae, Qiannanites Group, Prolecanitidae and Prodromitidae.
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A propos de : Michael R. House
Department of Geology, The University, Southampton, SO9 5NH, United Kingdom.