TAPHONOMY OF EARLY TRIASSIC GANOID FISH FOSSILS OF VEGA-PHROSO SILTSTONE MEMBER OF THE SULPHUR MOUNTAIN FORMATION NEAR WAPITI LAKE IN BRITISH COLUMBIA

Fish contain multiple elements that are sensitive to taphonomic processes. Many studies in freshwater lakes observe that fish carcasses are vulnerable to destruction due to buoyancy, surface transport, and ultimately disarticulation. The taphonomy of marine fishes is poorly known, perhaps as the result of postmortem buoyancy and transport. Ideally, the preservation of fully articulated marine fish would require deposition in quiet, anoxic waters, and a heavy surface scale covering to prevent sufficient accumulation of “decay” gas, and encourage sinking to the bottom. Triassic marine fishes with heavy ganoid scales are known from several localities including East Greenland, Spitzbergen, Madagascar and British Columbia, and offer a means to examine marine fish taphonomy. The ganoid fishes of British Columbia, found in the Vega-Phroso Siltstone Member of the Sulphur Mountain Formation are dated as Smithian Age, and are the focus of this research. The purpose of this research is to study ganoid fish taphonomy, specifically, how each type of fish decomposes, including anatomical location and extent of postmortem damage, and possibly, its cause. The exceptional preservation of these fish and the dark, fine-grained matrix indicates bottom water conditions were anoxic. An initial ranking system for the differing conditions of preservation include the range from a completely articulated specimen to the various degrees of disarticulation; skull (missing or present), body (missing or present), and pectoral, anal, caudal fins (missing or present). Initial research of approximately 200 museum specimens of the ganoid fish found near Wapiti Lake reveals the exceptionally preserved bony, ray-finned fishes Bobasatrania, Albertonia, Boreosomus, and lobe-finned coelacanth, Whiteia, show no signs of gas rupture of the abdomen. It is expected that continuing research will shed light on comparative preservation between species and possibly provide clues for the differences in preservation between bottom-dwelling and deep ocean dwellers, predator and prey.