Paleophysiology and End-Permian Mass Extinction

The Dutch ethologist Niko Tinbergen famously distinguished between proximal and ultimate explanations in biology. Proximally, biologists seek a mechanistic understanding of how organisms function; most of this volume addresses the molecular and physiological bases of biomineralization. But while much of biology might be viewed as a particularly interesting form of chemistry, it is more than that. Biology is chemistry with a history, requiring that proximal explanations be grounded in ultimate, or evolutionary, understanding. The physiological pathways by which organisms precipitate skeletal minerals and the forms and functions of the skeletons they fashion have been shaped by natural selection through geologic time, and all have constrained continuing evolution in skeleton-forming clades. In this chapter, I outline some major patterns of skeletal evolution inferred from phylogeny and fossils (Figure 1⇓), highlighting ways that our improving mechanistic knowledge of biomineralization can help us to understand this evolutionary record (see Leadbetter and Riding 1986; Lowenstam and Weiner 1989; Carter 1990; and Simkiss and Wilbur 1989 for earlier reviews).



 Figure 1. 
A geologic time scale for the past 1000 million years, showing the principal time divisions used in Earth science and the timing of major evolutionary events discussed in this chapter. Earlier intervals of time—the Mesoproterozoic (1600–1000 million years ago) and Paleoproterozoic (2500–1600 million years ago) eras of the Proterozoic Eon and the Archean Eon (> 2500 million years ago)—are not shown. Time scale after Remane (2000).



My discussion proceeds from two simple observations:



1. Skeletal biomineralization requires energy and so imposes a metabolic cost on skeleton-forming organisms.

2. Mineralized skeletons have evolved in many clades of protists, plants and animals.



If both statements are true, then clearly for many but not all eukaryotic organisms the biological benefits of biomineralization must outweigh its costs. But cost-benefit ratio is not static. It will change through …

Biomineralization and Evolutionary History

Extent, duration, and nature of the Permian-Triassic superanoxic event

Evidence for recurrent Early Triassic massive volcanism from quantitative interpretation of carbon isotope fluctuations

Precambrian clastic sedimentation systems

During the first step of the very rapid and large scale lowest Triassic transgression , we note in
different areas (S Alps, Taurus,Turkey, S Armenia, E Elburz, Iran, Central Iran and Central
Afghanistan) the growth of domal stromatolites, thrombolites and other microbial structures. At the
dawn of Triassic time, the carbonate factory was dominated by non-skeletal species and by
microrganisms able to precipitate carbonate.

/pdf/biosedimentology-of-microbial-buildups-igcp-project-no-380-3yhmmisf9c.pdf

Alexis Moussine-Pouchkine

Papers

Biosedimentology of Microbial Buildups IGCP Project No. 380 Proceedings of 2nd Meeting, Göttingen/Germany 1996

Is cratonic sedimentation consistent with available models? An example from the Upper Proterozoic of the West African craton

Pedogenetic and Diagenetic Fabrics in the Upper Proterozoic Sarnyéré Formation (Gourma, Mali)*