Abstract Lower Paleozoic palynomorphs show large morphologic diversity and are generally extremely abundant in unmetamorphosed marine sediments although the stratigraphic ranges and regional distribution of most taxa are still poorly known. Sufficient data are now becoming available to determine the distribution of palynomorphs in the Silurian System, and, to a lesser extent, in the Upper Ordovician and Lower Devonian. A number of contrasting, worldwide, acritarch biofacies existed in the regions bordering the Atlantic, in Arctic Canada, and in Siberia during the Silurian. Megafossil evidence indicates that these biofacies were contemporaneous and are regularly and predictably time-transgressive. Regionally the biofacies are not significantly correlative with local lithofacies. However, the lineations based on differences in acritarch assemblages approximately parallel lithotope boundaries and a causal relationship between them is suspected. On a Wegnerian palinspastic reconstruction of Atlantic Pangaea, the parallelism of biofacies lineations, lithotopes, and perhaps even paleomagnetic latitudes is conspicuous. We interpret this as reflecting regional paleotemperature differences. In order to account for the regional distribution of palynomorph biofacies in the lower Paleozoic, we propose a model that has mobile crustal blocks and essentially stable climatic conditions from Late Ordovician into Early Devonian time. Therefore, we interpret shifts in biofacies to be correlative with amount and rate of crustal movements. Because Silurian acritarch biofacies boundaries parallel paleoisotherms, they also parallel paleolatitudes. Supporting evidence includes: (1) the epeiric sea on Atlantic Pangaea had a minimum width of at least 45 degrees and probably had a pronounced latitudinal temperature gradient, (2) regionally continuous biofacies have a simple and regular geometry, (3) lithotopes and biofacies are parallel and their boundaries follow small circles, (4) regional biofacies are independent of such ephemeral factors as islands, troughs, and local sediment source changes, (5) bio facies form a transcontinental chronological and regional homotactic arrangement, (6) the biofacies are time-transgressive and follow a polar trajectory from Ordovician to Devonian pole positions.