Tonian, Cryogenian, and Ediacaran Periods

Tonian Period

The first section of the Neoproterozoic Era is the Tonian Period. It lasted from 1,000 million years ago to 720 million years ago. The breakup of supercontinent Rodinia began around 900-850 million years ago.

The first large evolutionary radiation of organic microfossils occurred during the Tonian Period. This means a huge increase in diversity caused by a large rate of specialization. None of the examples in this article of evolutionary radiation were from the Tonian period, however, probably since it involved microfossils, which most lay people are not terribly familiar with.

So, Rodinia started breaking up, and microorganisms multiplied and diversified. It still sounds like a pretty barren place to me.

Cryogenian Period

The second geologic period of the Neoproterozoic Era was the Cryogenian Period, lasting from 720 to 635 million years ago. There were 2 ice ages during this period, the Sturtian and Marinoan Glaciations, which are said to be the greatest ice ages known on Earth. There is much debate over whether these glaciations covered the entire planet (Snowball Earth) or a band of open sea survived near the equator (Slushball Earth).

In any case, the Sturtian Glaciation lasted from 720 to 660 million years ago, while the Marinoan Glaciation ended at approximately 635 million years ago, although there was no indication when it began. Whenever it began, it was relatively short-lived when compared to the Sturtian.

Fossils of hard-shelled amoeba first appear during this period, as well as the oldest known fossils of sponges. Debate about how much the glaciation might have impacted biology rages on, with some suggesting that several species began during this period.

Me, I much prefer warmer climes.

Ediacaran Period

The end of the Era is marked by the Ediacaran Period, which lasted from 635 million years ago to 541 million years ago.

Fossils from the Ediacaran are sparse, as not a lot of hard-shelled animals had yet evolved. But there were multicellular organisms with specialized tissues. The most common types resemble segmented worms, fronds, disks, or immobile bags. Although Ediacara biota bear little resemblance to modern lifeforms, more than 100 genera have been described.

During this period, the moon was considerably closer, making the tides stronger and more rapid than they currently are. A day was about 21.9 hours long, meaning there were about 13.1 months per year, and approximately 400 days/year.

Okay, now we're getting somewhere. The place had worms and fronds, or at least lifeforms that looked like them. I was particularly pleased with the information about the days being shorter and the moon being closer. How long do you suppose it would take human colonists to get used to a 22-hour day instead of a 24-hour day?

 

https://en.wikipedia.org/wiki/Tonian#:~:text=The%20Tonian%20(from%20Greek%20%CF%84%CF%8C%CE%BD%CE%BF%CF%82,Mya%20(million%20years%20ago).&text=The%20Tonian%20is%20preceded%20by,and%20followed%20by%20the%20Cryogenian.

https://en.wikipedia.org/wiki/Evolutionary_radiation

https://en.wikipedia.org/wiki/Cryogenian#:~:text=The%20Cryogenian%20(%20%2Fkra%C9%AA,and%20followed%20by%20the%20Ediacaran.

https://en.wikipedia.org/wiki/Ediacaran