Elias R.J.,University of Manitoba |
Young G.A.,The Manitoba Museum |
Lee D.-J.,Andong National University |
Bae B.-Y.,Seoul National Science Museum
Geological Society Memoir | Year: 2013
During the Late Ordovician, Cincinnatian, the epicontinental seas and continental margin of Laurentia provided habitats that were suitable for corals. Biogeographical differentiation occurred within this equatorially placed continent, when corals were introduced to areas that had fundamentally different environments. There were four biogeographical divisions, characterized by distinctive faunas that included some endemic taxa: the Red River-Stony Mountain Province, Richmond Province, Edgewood Province and the less well understood, informal 'Continental Margin' Area. In each division, the potential for diversification and the capacity for diversity were determined by factors such as the duration and size of the division, the amount of immigration, the extent of evolution and biogeographical differentiation, faunal responses to changes in sea-level and climate, and the complexity of the ecological structure. The development of multiple biogeographical divisions, each contributing to overall diversity, enhanced the 'Great Ordovician Biodiversification Event'. During the latest Ordovician mass extinction, there was a reduction of diversity and loss of biogeographical divisions within Laurentia. The divisions were terminated when their characteristic taxa disappeared, in response to major environmental changes associated with glaciation in Gondwana and subsequent global warming. © The Geological Society of London 2013.
Bae B.-Y.,Seoul National Science Museum |
Elias R.J.,University of Manitoba |
Lee D.-J.,Andong National University
Lethaia | Year: 2013
Four species of the tabulate coral Catenipora are present in the Selkirk Member of the Red River Formation at Garson, Manitoba. They provide an opportunity to compare the growth characteristics of multiple, co-occurring species that produced cateniform coralla. Corallite increase, cyclomorphism and other growth features show high variability within and/or among the species. A total of five types of lateral increase and two types of axial increase are recognized. Lateral increase accounts for over 80% of all occurrences of corallite increase in each species, with the four species differing significantly in the relative frequency of the various types of lateral increase. The type of axial increase, megacorallites and agglutinated patches of corallites that developed from normal, undamaged corallites in C. foerstei are species specific. In all species, cyclic fluctuations in the tabularial area of corallites are considered to be annual, and the variable growth rates within colonies and species are attributed to differences in astogenetic stages or environmental conditions. Average annual vertical growth was positively correlated with average tabularial area in C. foerstei, C. cf. robusta and C. rubra. Catenipora cf. agglomeratiformis, however, which had the lowest average tabularial area and greatest sensitivity to sediment influx, had a high average growth rate comparable to that of C. rubra, which had the largest average tabularial area. The formation of ranks or lacunae by certain types of lateral increase seems to have been the most effective strategy for maintaining and/or expanding the colony growth surface in all four species, and was most common in C. cf. agglomeratiformis. A reptant growth pattern, characterized by creeping ranks, permitted effective recovery of damaged parts as well as quick formation of new ranks or lacunae. The growth surface of these species was situated near the sediment-water interface. □Growth characteristics, intraspecific variation, interspecific variation, palaeobiology, tabulate corals. © 2012 The Authors, Lethaia © 2012 The Lethaia Foundation.