The Rapidian has a feature on prehistoric Michigan’s tropical seas, jungles and inhabitants that’s a great read and the ultimate Throwback Thursday! Here’s a small slice:
After about 60 million years, warm, shallow seas came down again from the Arctic and covered Michigan during the Silurian period. At this time the land would have been in a subtropical climate that gave rise to large coral reefs across the state. Fossil findings show that the largest and oldest reef extends through the center of the Upper Peninsula. A species of coral that lived during this time period would eventually become fossilized and become what we refer to as Petoskey Stones.
The seas retreated over time, leaving a desert scattered with fossilized remains that eventually formed the limestone that is located over one hundred and twenty feet below us today. The sections of this exposed limestone is what created the Grand Rapid’s famous rapids. Much of the salt deposits that were left from retreating seas of this period are still mined in Detroit.
The Devonian period around 400 million years ago saw the rise of vertebrates in Michigan. North America was covered with up to 40 percent of water. There were a great number of fish swarming the salt and fresh water seas. The Ganoid species were in a crude state of evolution. Many of them had armor plating with two of their relatives, the Gar Pike and the Sturgeon, still existing in Great Lakes today. Primitive plants, such as the seed fern, developed from marine algae. On land the Tiktaalik, the link between finned fish and early amphibians, started to use its muscular fins to drag itself around land.
…At the end of the Carboniferous Period, known as the Pennsylvanian subperiod, Michigan was a semi-tropical jungle featuring primitive vegetation. Ferns without bark, some of which bloomed scentless unattractive flowers, grew to almost 100 feet. Millions of generations of trees grew and died in the jungle. The trees that fell in the swampy parts of the jungle were covered up by water and soil that became rock over time. The forces of time and pressure on these trees would eventually see this prehistoric jungle become the coal basin that sits underneath a large area of the U.S. including the upper northeast part of Kent county.
In the sky above one foot long dragon flies swarmed in droves on the ground and cockroaches the size of a man’s palm crawled around. Reptiles started to appear, evolving from amphibians, not dependent on water to lay their amniotic eggs. Towards the end of this period the rain forests gave way to deserts which decreased the amphibian populations and caused an evolutionary shift in reptiles.
Definitely click through for more – there are some cool links as well!