Geological Magazine

Rapid Communications

Phosphatized soft tissues in bivalves from the Portland Roach of Dorset (Upper Jurassic)

Philip R. Wilbya1 and Martin A. Whytea2

a1 Department of Geology, Wills Memorial Building, Queen’s Road, Bristol, BS8 1RJ, UK

a2 Department of Earth Sciences, Dainton Building, University of Sheffield, Sheffield, S3 7HF, UK

Abstract

Phosphatized soft tissues are preserved in abundance in the trigoniids (Bivalvia) Laevitrigonia gibbosa and Myophorella incurva from the Portland Roach (Upper Jurassic) of Dorset. Cellular structures are preserved and fossilization is almost exclusively the result of a dense coating of mineralized microbes. Phosphatized soft tissues are restricted entirely to those trigoniids whose valves remained tightly closed after death. Only in these specimens was sufficient phosphorus concentrated by the decay of their most ‘labile’ soft tissues to trigger the precipitation of apatite in and around microbes infesting their more ‘refractory’ soft tissues. The absence of fossilized soft tissues in the rest of the fauna implies that phosphatization was very taxon-specific.

(Received June 20 1994)

(Accepted September 20 1994)

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