Taphonomy of Early Triassic fish fossils of the Vega-Phroso Siltstone Member of the Sulphur Mountain Formation near Wapiti Lake in British Columbia

The taphonomy of fishes living in lacustrine environments has been extensively studied in both the laboratory and the fossil record; the taphonomy of marine fishes, however, is poorly known. Triassic marine fishes with heavy ganoid and cosmoid scales, which provided protection from rapid taphonomic loss, offer a means to examine marine fish taphonomy in the fossil record. Four genera of Early Triassic fishes (the ray-finned Albertonia, Bobasatrania, Boreosomus, and the lobe-finned coelacanth, Whiteia) from the Wapiti Lake, British Columbia locality of the Vega-Phroso Siltstone Member of the Lower Triassic (Smithian) Sulphur Mountain Formation were examined in order to study the taphonomy of marine fishes and to gain a better understanding of the taphonomy of fish in marine environments, examine ambient environmental conditions during deposition of the fish, and determine the habitat and mode of life of the fish. Results indicate that environmental conditions that contributed to the preservation of the fossil fishes of the current study included deposition in deep, quiet waters, which reduced the odds of disarticulation, colder waters under higher pressure, which lowered metabolic rates of bacteria and limited postmortem floatation, and waters that were anoxic, which discouraged predators and scavengers. In addition, the thickness of the primitive ganoid and cosmoid scales of the fossil fishes also increased their preservation potential. The examination of ancient fish with ganoid or cosmoid scales may provide future avenues of research to gain a better understanding of marine fish taphonomy, and possibly provide information about ancient fish behavior and their environment.