The second period of the Upper Palaeozoic era from about 345 to 280 million years ago. During this period the climate was generally warm and humid and there were great forests and swamps, dominated by arborescent lycopsids and sphenopsids, from which the coal measures were formed. In the US the term Carboniferous is not widely used because rocks of this age in North America can be separated into two distinct types. American geologists refer to rocks of the Lower Carboniferous (345-310 million years ago) as Mississippian and of the Upper Carboniferous (310-280 million years ago) as Pennsylvanian. In North America only the Pennsylvanian rocks contain coal. Carboniferous fossil remains include mosses and liverworts, and herbaceous lycopsid fossils similar to present-day Lycopodium and Selaginella are abundant. Some of the arborescent lycopsids, as represented by Lepidodendron (see Lepidodendrales), appear to have had a rudimentary ovule. The sphenopsids are represented by the now extinct arborescent Calamitales (giant horsetails) and the extinct herbaceous Sphenophyllales. Equisetites hemingwayi in the Upper Carboniferous is one of the few herbaceous forms resembling the present-day Equisetum. The ferns were well represented as were the gymnosperms with fossils of the * Pteridospermales, * Cordaitales , and * Coniferales all being found. See geological time scale. |
