Devonian reef-associated articulate red algae from western Canada.

Abstract

Documents the existence in Upper Devonian reefs of articulate calcareous red algae homologous with the modern articulate coralline genus Amphiroa. The habitat range of these algae has been profiled across a 30-mile (48 km) outcrop transect of the Frasnian Alexandra Reef-Complex southwest of Hay River in Canada's Northwest Territories. Their occurrences are inversely related to lagoon-dwelling organisms such as dasycladacean and codiacean algae, calcispheres, and Amphipora. Dolomite rhombs preferentially replacing many of the fragments suggest an original mineralogy of high-magnesian calcite such as characterizes modern coralline algae. Close correspondence in structure, inferred mineralogy and habitat between this alga, informally referred to as Archaeoamphiroa, and the living Amphiroa suggests a phylogenetic linkage, and it is recommended that Archaeoamphiroa be classified with the articulate coralline subfamily Amphiroideae. Furthermore, because the ontologic history of articulate coralline algae indicates an encrusting precursor, documentation of these algae supports evidence previously cited for the existence of crustose coralline algae in the Devonian. -from Author