Pseudomyona from the Cambrian of North Greenland (Laurentia) and the early evolution of bivalved molluscs

• The laterally compressed, univalve, Cambrian (Miaolingian Series, Drumian Stage) mollusc Pseudomyona is recorded for the first time from Laurentia. Distinctive internal moulds of the type species Pseudomyona queenslandica, a species otherwise known from Australia and northern Siberia, are described from the Ekspedition Brae Formation of southern Lauge Koch Land, North Greenland. A new species, Pseudomyona groenlandica, characterised by a proliferation of hinge teeth on the supra-apical surface, is described from the overlying Fimbuldal Formation of south-east Freuchen Land. The increase in hinge teeth supports the hypothesis that the bivalved Tuarangia from the Miaolingian Series (Guzhangian Stage) of New Zealand and Bornholm, Denmark, evolved from Pseudomyona. Although bivalved, Tuarangia is not interpreted as Class Bivalvia, but as the most derived member of an early clade in the evolution of Class Rostroconchia. The emended Order Tuarangiida, containing Tuarangia and Pseudomyona, forms a sister group to ribeirioids and later rostroconchs

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geology (hsv//eng)

Nyckelord

Mollusca

Rostroconchia

Bivalvia

Cambrian (Miaolingian)

Greenland

Laurentia

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