Final answer:
The Mesozoic Marine Revolution (MMR) is marked by major evolutionary changes and mass extinction events. The extinction at the end of the Triassic period was possibly due to increased CO₂ from volcanic activity. The fossil record, including the transition from trilobites to ammonites and changes in marine diversity, highlights the substantial biological shifts during the MMR.
Step-by-step explanation:
Traces of the Mesozoic Marine Revolution
The Mesozoic Marine Revolution (MMR) is characterized by significant evolutionary changes among marine organisms during the Mesozoic era, which includes the Triassic, Jurassic, and Cretaceous periods. A well-documented mass extinction event is evident at the boundary between the Triassic and Jurassic periods, around 201.3 million years ago (Ma), characterized by the disappearance of approximately 25-30% of all marine species. This mass extinction was likely due to environmental changes caused by increased atmospheric CO₂ levels resulting from the volcanic eruption of a large igneous province in the Atlantic Ocean.
In the fossil record, stratigraphic changes signal these extinction events. The Lilstock Formation represents the Triassic in this context, showing a warm tropical ocean teeming with life. Then the Blue Lias Formation, indicative of the early Jurassic, is recognized for its wealth of fossil ammonites. The shift from the dominance of trilobites to the diversification of ammonites and their subsequent extinction, the temperature rise through various periods such as the end-Permian, and the mass extinctions at the end of geological periods such as the Triassic-Jurassic, are significant events of the MMR.
The late Paleozoic era also saw diversification in vertebrates, including the amniotes which eventually gave rise to various lineages including mammals and dinosaurs. Mass extinctions impacted both marine and terrestrial vertebrates, greatly influencing the direction of evolution. These patterns are observable through detailed geochemical and stratigraphic studies, as well as fossil records as evidenced in various scientific findings, like those of Alroy et al. (2008) and publications in Science.