The Devonian Period was followed by the Carboniferous Period which lasted from 359 to 299 million years ago. Terrestrial life was well established by the Carboniferous period, and vast swaths of forest covered the land. Amphibians were the dominant land animals, although insects were also very common with many such as Meganeura being much larger than their dragonfly decedents today. The atmospheric content of oxygen also reached their highest levels in history during the period, 35%(1)David Beerling (2007) The emerald planet: how plants changed Earth’s history, Page 47 compared with 21% today. This increased the atmospheric density by a third compared to the current density. During the Carboniferous Period the first reptiles appeared in the fossil record as small lizards.
Late in the period, around 305 million years ago, a minor extinction event took place called the Carboniferous Rainforest Collapse. The cause is not known, however it appears that the chief cause was the fragmentation of Pangaea’s once massive equatorial rainforest into many smaller isolated rainforests. Previously the same species of animals had been present throughout the continental rainforest, however after its fragmentation many terrestrial amphibian species became extinct allowing the reptile community to diversify greatly after the extinction event.(2)Sarda Sahney et al. (2010). “Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica.” Geology, Volume 38, Number 12, Page 1079–1082
The depletion of plant life contributed to the deteriorating levels of oxygen in the atmosphere, which caused the extinction of the enormous insects of the time. This sudden collapse affected several large groups. Labyrinthodont amphibians were particularly devastated, while reptiles fared better being ecologically adapted to the drier conditions that followed. Amphibians lay eggs in water, in contrast to reptiles whose eggs have a membrane allowing gas exchange out of water and can therefore reptile eggs can be laid on land. Reptiles acquired new niches at a faster rate than before the collapse and at a much faster rate than amphibians. Reptiles expanded their diet to include plants, amphibians, and other reptiles, having previously only eaten fish and insects.
The fragmentation of Pangaea’s rainforest into multiple smaller rainforests also appears to be something humanity would have done at the time, as we have done the same thing to multiple rainforests since then. The Amazonian and Congo rainforests are currently being fragmented in the same way the Pangean rainforest appears to have been fragmented. However there again appears to be no evidence of a quasi-intelligent species having evolved on the planet at the time, leaving as a possibility extraterrestrial colonists.
References [ + ]
|1.||⇑||David Beerling (2007) The emerald planet: how plants changed Earth’s history, Page 47|
|2.||⇑||Sarda Sahney et al. (2010). “Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica.” Geology, Volume 38, Number 12, Page 1079–1082|