Siliceous Tablets in the Larval Shells of Apatitic Discinid Brachiopods
Alwyn Williams,
*
Maggie Cusack,
James O. Buckman,
Thomas Stachel
The marine bivalved Brachiopoda are abundant throughout the
geological record and have apatitic (CaPO4-rich) or
calcitic (CaCO3-rich) shells. Vesicles covering the larval
valves of living apatitic-shelled discinids contain tablets of silica.
The tablets are cemented into close-packed mosaics by spherular apatite
in glycosaminoglycans. They are usually lost as vesicles degrade but
leave imprints on the underlying apatitic shell. Similar imprints
ornament larval surfaces of some of the earliest Paleozoic
apatitic-shelled brachiopods and may also be indicators of siliceous
biomineralization.
A. Williams and J. O. Buckman, Palaeobiology Unit, University
of Glasgow, Glasgow G12 8QQ, UK.
M. Cusack, Department of Geology and Applied Geology, University of
Glasgow, Glasgow G12 8QQ, UK.
T. Stachel, Institute of Mineralogy, Johann Wolfgang Goethe-University,
Frankfurt D-60054, Germany.
*
To whom correspondence should be addressed.
