From: David A Gabel, ENN
Published December 3, 2010 09:48 AM

Prehistoric Reptilian Diversity Caused by Rainforest Collapse

At 300 million years ago, global warming brought about an abrupt collapse of tropical rainforests. According to a new study, it is now believed that this event spawned the evolutionary burst of reptiles. It gave rise to the dinosaurs, which dominated the globe for over 150 million years.

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Over its lifetime, the Earth has been through a number of dramatic extinction events, such as the extinction of the dinosaurs 65 million years ago and the extinction of 95% of all life 250 million years ago. These traumatic events are all generally followed by a period of growth in diversity, led by survivors of the global catastrophe.

The event that occurred 300 million years ago occurred in the Carboniferous Period, a time known for glaciation, low sea levels, and mountain building. It is named Carboniferous from the Latin word for coal, carbo, because it is believed that many coal beds were laid down during this period. At the time, Europe and North America lay along the equator and were homes to massive rainforests, known as coal forests. Global warming triggered by unknown reasons caused the collapse of these equatorial forests.

A new study published in the journal, Geology, suggests that this collapse gave rise to an explosion of diversification among reptiles in Europe and America. The reptiles were better adapted to handle the drier conditions caused by global warming and more readily adjusted to new feeding patterns. Ecologically, these early reptiles, also known as tetrapods, were well suited for the ensuing habitat fragmentation and resource restriction.

Dr. Howard Falcon-Lang of Royal Holloway, University of London and co-author of the study explained, "Climate change caused rainforests to fragment into small 'islands' of forest. This isolated populations of reptiles and each community evolved in separate directions, leading to an increase in diversity."

The researchers examined fossils of reptiles before and after the rainforest collapse. The fossil records showed reptiles become more diverse as they struggled with a changing environment.

Over millions of years, their numbers grew as well as their diversity. They would not dominate the landscape until the reign of the dinosaurs in the Triassic period (230 million years ago). But the events at 300 million years ago lay the groundwork for their rise.

Link to published article: http://geology.gsapubs.org/content/38/12/1079.abstract

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