endDevonian

The term "end-Devonian" refers to the final stage of the Devonian Period, which spanned from approximately 419.2 million to 358.9 million years ago. This era is the fourth of six periods in the Paleozoic Era and is notable for significant geological and biological events that culminated in one of the most severe mass extinctions in Earth's history.

The end-Devonian marks the transition from the Middle Devonian to the Early Carboniferous Period. During this time, Earth's climate experienced dramatic shifts, including a series of glacial episodes that began in the Late Devonian. These glacial events, particularly the Kaskaskia glaciation, led to a drop in sea levels and widespread environmental changes. The cooling climate and fluctuating sea levels contributed to the decline of many marine and terrestrial ecosystems.

One of the most defining features of the end-Devonian is the Hangenberg Crisis, a mass extinction event that occurred around 359 million years ago. This event caused the extinction of approximately 50% of marine life and a significant portion of terrestrial species. The extinction affected various groups, including coral reefs, fish, and early tetrapods (four-limbed vertebrates). The exact causes of the Hangenberg Crisis remain debated, but hypotheses include anoxia (lack of oxygen) in ocean waters, volcanic activity, and changes in ocean chemistry due to glacial activity.

The end-Devonian also witnessed the diversification of early tetrapods, which were transitioning from aquatic to terrestrial life. Despite this evolutionary progress, many groups failed to survive the mass extinction, reshaping the ecological landscape for the subsequent Carboniferous Period. The end-Devonian thus serves as a critical period in Earth's history, illustrating the interconnectedness of climate, geology, and biodiversity.