Taxonomy, Ecology and Palaeoenvironment of Mesozoic Marine Bivalves: Patterns and Processes

Nandi, Snehil (2022) Taxonomy, Ecology and Palaeoenvironment of Mesozoic Marine Bivalves: Patterns and Processes. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Snehil Nandi (17MS220)) 17MS220_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

The Mesozoic Era witnessed a major revolution in the marine realm. The turnover from the Palaeozoic Fauna to the Modern Fauna was accompanied by a rise in predation and competition pressure, which along with a slew of abiotic factors, changed the structure of biotic communities in oceans around the world. Clade-specific analyses of taxonomic diversity, ecology and palaeoenvironments are performed to realize the effects of these changes in one of the most successful groups of marine organisms - the Class Bivalvia. Further analyses are performed to understand how these trends covary with each other and match upto global patterns recognized for the marine invertebrate paleo community as a whole. My analyses reveal: (1) taxonomic diversity experienced an enormous rise with phases of clade elimination in between, coinciding with two mass extinction boundaries; (2) ecological attributes pertaining to tiering, feeding and motility witness a rise in generic representation. The transition in dominance of infauna over the surface epifauna is one major pattern that was typical of the Mesozoic. Feeding habits, however, remained unaltered throughout; and, (3) choice of palaeoenvironments seldom varied across the Mesozoic, with the highest diversity concentrated at the shelf and reef regions. The Mesozoic Marine Revolution, which involves origination of diverse durophagous molluscivore taxa, grazers and “biological bulldozers” - deposit feeders that disturb the sea surface sediments by mixing and reworking, is speculated to have played a huge role in bringing about these changes that went a long way in shaping the modern marine ecosystem as we know it today. Certain abiotic factors like active tectonism along major magmatic zones, and consequent palaeoclimatic changes had immediate detrimental effects, but recoveries post these catastrophes were quick enough to restore the mercurial rate in increment of taxonomic diversity.

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