Mid-Devonian to mid-Permian floral and faunal regions and provinces

Summary The middle to late Palaeozoic biota in seas adjacent to the Caledonide-Appalachian orogen included an abundant generally cosmopolitan benthos in both carbonate and clastic environments. Where low clastic sediment input permitted, organic reefs and build-ups were characteristic of this tropical area. Early Devonian biogeographic provinces did not persist into later times. The pelagic fauna, dominated by ammonoidea, bivalvia, conodonts and vertebrates, was rich, rapidly evolving and, again, cosmopolitan. Vertebrates and conodonts in particular were wide ranging. Among the land plants heterospory and arborescence evolved during the middle and late Devonian in a number of classes, particularly the Lycopsida and Progymnospermopsida. Genera were largely cosmopolitan during this time, and only one floristic region can be recognized worldwide, although there is some evidence for slight provincial floral variation outside Laurussia. During the early Carboniferous arborescent Lycopsida were abundant. Three floristic regions can be identified worldwide, of which one is the Circum-Tethyan Region including Laurussia, Kazakhstania and China. Two floral provinces are recognized within the Laurussian part of this region. In late Carboniferous and early Permian times, when gymnosperms replaced the pteridophytes as the dominant forms, there is a more clear-cut separation of floral regions, and by early Permian two floral regions are recognized within Laurussia which are clearly different from those away from this land mass. Non-marine bivalvia and vertebrates were highly cosmopolitan from mid-Devonian time onwards, with amphibia appearing in Greenland in the late Devonian and reptiles appearing in eastern Canada and western Europe in Westphalian A time.