Review and palaeoecological analysis of the late Tremadocian – early Floian (Early Ordovician) cephalopod fauna of the Montagne Noire, France

By comparison with the relatively diverse Early Ordovician cephalopod faunas that lived in association with the low latitude carbonate platforms (e.g. Laurentia [Flower 1964]; Siberia [Balashov 1961]; China [Chen 1976]), those of the high latitude margins of Gondwana are of relatively low diversity, generally poorly known, and where known, often in need of revision. Of those high latitudinal assemblages most recently revised or newly described in detail (Evans 2005; Gnoli & Pillola 2002; Marek et al. 2000), all seem to be characterized by the presence (often in abundance) of members of the family Eothinoceratidae. In revising the early ordovician cephalopod faunas of England and Wales (eastern Avalonia), Evans (2005) recorded the presence of the Orthoceratoidean families Baltoceratidae, Polymeridae and Troedssonellidae from sediments of early Floian age. Until now, this particular fauna contained the oldest unequivocal record of the Orthoceratoidea. One interpretation that may be put upon their occurrence in such a location is the possibility that the Orthoceratoidea might have originated in a region of high palaeolatitude. Such an interpretation, based upon a single geographical datum, remains tentative.