See more from this Division: Topical Sessions
See more from this Session: Paleontological and Sedimentological Consequences of Calcite and Aragonite Sea Dynamics
Abstract:
After skeletons evolve, however, the influence of changing aragonite-calcite seas on skeletal mineralogy appears to drop. Oscillations in seawater chemistry may affect the relative success of aragonitic vs. calcitic taxa and may cause fluctuations between low-Mg- and high-Mg-calcite mineralogy within a clade, but there are relatively few examples of an evolutionary switch from aragonite to calcite biomineralization or vice versa. Many reports of mineralogical switching instead likely reflect de novo acquisition of skeletons in a non-mineralizing clade or environmental conditions overriding biological control of mineralization.
A possible explanation for these observations is that natural selection for reduced energetic costs dictates the initial choice of mineralogy. However, because shell mineralization involves a diverse suite of proteins, many polymorph-specific, switching skeletal mineralogies may require the evolution of a new and extensive array of proteins. As a result, once mineralization has evolved, the cost of switching mineralogies may be greater than that of producing a mineralized skeleton not favored by seawater. How and why a few taxa, including molluscs and bryozoans, apparently did switch mineralogies is not known.
See more from this Division: Topical Sessions
See more from this Session: Paleontological and Sedimentological Consequences of Calcite and Aragonite Sea Dynamics