About 360 million years ago, a significant mass extinction event struck the Earth, dramatically impacting marine life, particularly fishes. This event marked the end of the Age of Fishes.
The Devonian Mass Extinction
This extinction event, known as the Late Devonian extinction, significantly reduced the diversity and size of vertebrate species in the oceans.
- Impact on Fish: The extinction event disproportionately affected larger fish species, effectively shrinking the average size of vertebrate species to the size of a human forearm or smaller. The seas which were filled with myriad fishes, including creatures the size of school buses, were affected.
- Cause: The exact cause of the Late Devonian extinction is debated, but several factors likely contributed:
- Changes in Sea Level: Fluctuations in sea level could have disrupted marine habitats.
- Volcanic Activity: Increased volcanic activity might have released gases that altered the atmosphere and ocean chemistry.
- Asteroid Impacts: While less certain, asteroid impacts are also considered potential triggers.
- Oxygen Depletion: Reduced oxygen levels in the oceans may have suffocated many marine organisms.
Effects
The Late Devonian extinction was one of the "Big Five" mass extinction events in Earth's history. The effects included:
- Loss of Biodiversity: Significant reduction in the number of species, particularly in marine environments.
- Shift in Dominant Species: The extinction paved the way for the evolution and diversification of new species in the aftermath.
- Altered Ecosystems: The structure and function of marine ecosystems were fundamentally changed.
In conclusion, around 360 million years ago, the Late Devonian extinction profoundly impacted marine life, especially fishes, leading to a dramatic decline in size and diversity. This event reshaped marine ecosystems and set the stage for future evolutionary developments.
