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Palaeobiology of a Biradiolites mooretownensis rudist lithosome: seasonality, reproductive cyclicity and population dynamics





Dominik K. Hennhöfer [] and Stefan Götz, Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany; Simon F. Mitchell. [], Department of Geography & Geology, The University of the West Indies, Mona, Kingston 7, Jamaica; manuscript received on 23/09/2011; manuscript accepted on 15/12/2011.


Hennhöfer, D., Götz, S. & Mitchell, S.F. 2012: Palaeobiology of a Biradiolites mooretownensis rudist lithosome: seasonality, reproductive cyclicity and population dynamics. Lethaia, Vol. 45, pp. 450–461.

During the Cretaceous, rudist bivalves were among the most important benthic carbonate producers on tropical to sub-tropical carbonate platforms. Yet questions concerning the biology of rudist bouquets remain unanswered to a great extent. In this study a monospecific bouquet of the small radiolitid rudist Biradiolites mooretownensis has been evaluated from a palaeobiological angle. Three-dimensional, high-resolution, quantitative analysis provides a detailed evaluation of growth and reproduction in an in situ rudist association. A total of 1237 consecutive tomograms with a vertical spacing of 0.1 mm were produced of which 1150 have been digitally measured for total area, number of specimens, packing density, spat density, recruitment, survival time, mortality and accommodation space. The results show constant coverage of about 60%, a stable packing density of 3.2 specimens per cm2 and constant reproduction throughout the bouquet. Time series analysis (spectral analysis) using PAST statistical software shows cyclic spat density every 14.9 mm of vertical growth. Combined with the results of the δ18O isotope analysis (showing cyclicities of 14 mm) one reproduction cycle appears to be annual. 46.4% of all counted specimens died before 3 mm of vertical growth. More than 93% of the initial spat does not exceed 15 mm shell height or 1 year respectively. Two mortality peaks in the juvenile’s life at 4 and 10–15 mm shell height either represent important obstacles in the ontogenetic development of the species or reflect external influences. □ Biradiolites, grinding tomography, palaeobiology, population dynamics, reproduction, rudists, sclerochronology, seasonality.