Unverified50% confidenceFactExact time
During the Carboniferous period (approximately 300 million years ago), atmospheric oxygen levels reached 35%—compared to 21% today—and the high oxygen levels increased the efficiency of tracheal diffusion, enabling the appearance of giant dragonflies with wingspans of up to 70 centimeters.
1
Sources
50%
Confidence
Long-term
Relevance
8/18/2026
First Seen
Sources
伽利略平方立方定律：为什么巨人在物理上不可能存在
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