ABSTRACT
A Late Pleistocene locality (approx. 80 ka) in the Wanganui Basin, New Zealand, has yielded large numbers of the brachiopod Calloria inconspicua displaying original shell colouration. In total 78% out of a collection of 377 fossil shells show orange-red colouration that represents a partial degradation of the stronger red colour found in living representatives. Investigation of a modern-day population of the species from New Zealand from an intertidal habitat indicates that recently deceased individuals rapidly lose all of their colouration. Only 57% of 281 individuals collected from the sediment surface beneath this modern population retained any trace of shell colour, and this proportion dropped to 46% of the 321 shells in the top 50 mm of sediment. As other brachiopods and molluscs at the Late Pleistocene locality also revealed traces of original colouration, preservational conditions must favour the survival of the pigments responsible for shell colouration. The colouration of Calloria inconspicua is caused by a caroteno-protein embedded within the shell, which is susceptible to degradation in the presence of light and oxygen. Rapid burial may retard the processes of degradation, and such an interpretation is consistent with the occurrence of the fossil brachiopods in an intertidal pebble bed. Colouration of the shell may help camouflage the brachiopod; the same colouration in the free-swimming larvae may offer protection from radiation damage.
Gordon B. Curry, Division of Earth Sciences, Gregory Building, University of Glasgow, Glasgow, G12 8QQ, Scotland
KEY WORDS: Pleistocene, shell colour, brachiopod, New Zealand
Copyright: Palaeontological Association,
October 1999
Submission: 6 June 1999, Acceptance: 9 September 1999