Article: The mid-Proterozoic Little Dal macrobiota, Mackenzie Mountains, north-west Canada

The Little Dal macrobiota is now known to comprise the previously reported carbonaceous megafossils Chuaria circularis, Tawuia dalensis, Moranial antiqua, and Beltina danai, as well as the following additional taxa: Longfengshania stipitata, Grypania spiralis, Daltaenia mackenziensis n.g. and sp., Tyrasotaenia sp., and Tyrasotaenia? sp. The dubiofossil 'Bergaueria?' reported earlier is probably nonbiogenic.Of special interest are three-dimensionally preserved specimens of Chauria, Tawuia, and Tyrasotaenia?, found associated with 'molar-tooth' structure. A carbonized test separates the pure, equigranular, microcrystalline calcite infilling of the fossil interior from an argillaceous carbonate matrix. This infilling is optically and chemically indistinguishable from that comprising the 'molar-tooth' structure. These relationships indicate comparable processes and timing for both fossilization of the organisms and filling of syneresis cracks during compaction and consolidation of the sediment.