Paleoecological parallelism between the Angaran and Euramerican phytogeographic provinces

Abstract

Comparisons between plant fossil assemblages occurring in similar depositional settings in Angara and Euramerica indicate that both provinces contain similar ecological niches occupied by similar biomorphs. However, there is almost complete substitution of species and genera between the provinces. In Euramerica, the peat swamps were dominated by lycopsids, in Angara by cordaites. Lycopod dominated forests occurred in Angara, but never became major peat formers. Floras colonizing the margins of water bodies, whether marine, lacustrine, or fluvial, are dominated by mostly cosmopolitan sphenopsid taxa (though there is some endemism in Angara toward the end of the Carboniferous) and endemic bryophyte floras. The clastic lowlands were dominated by pteridosperms in both provinces. Because of the variety of ecological niches in lowland environments and the difficulty in dispersing propagules from such habitats, there is tremendous species diversity and a high degree of endemism in Euramerican and Angaran lowland environments. Climatic differences between the provinces also contribute to this endemism. Euramerica was characterized by tropical conditions while Angara was characterized by temperate conditions exhibiting seasonal temperature and humidity fluctuations.