Permian Period Part 2

 Mammals and reptiles could cope with the desert conditions better than amphibians, and so rose to dominate the Permian. Such dry conditions favored plants with seeds enclosed in a protective cover, rather than plants like ferns, that disperse spores. Modern trees like conifers, ginkgos and cycads appeared in the Permian.

On land, life included diverse plants and fungi. At first, a lot of the Carboniferous flora still flourished. But around the middle of the period, a massive desert covered the interior of Pangaea, and there are indications that the desert was devoid of vegetation. Even in areas where it wasn't such a stark desert, more advanced seed ferns and early conifers moved in. A number of types of plants and animals died out or became marginal elements. By the end of the Permian, swamps reminiscent of the Carboniferous survived only on a series of equatorial islands east of Pangaea that would later become South China.

The Permian saw the diversification of many important conifer groups, including ancestors of many present-day families. Rich forests were present in many area, with a diverse mix of plants. Southern Pangaea saw extensive seed fern forest, and oxygen levels were probably high there. The ginkgos and cycads also appeared.

Insects were very prevalent during the Permian, especially considering that 90% of the insects at the start of this period were cockroach-like insects. Primitive forms of dragonflies were the dominant aerial predators. Several insect groups appeared or flourished during this time, including beetles, true bugs and others.

Larger 'more advanced' types of animal life included reptiles and amphibians. A number of the reptiles seemed to be what I call the 'sail-backed' lizards, where they have bone ridges protruding from their spine and covered in skin. Some of these were herbivore and some were carnivore. I didn't find any indication of how large they might have gotten.

At some point, amphibians declined, and at least one family of the 'sail-backed' lizards was replaced with more advanced animals, including mammals and mammal-like animals. Towards the very end of the period, the first archosauriforms appeared. These were reptiles that possibly rose from the crocodile family and would go on in the next period to produce dinosaurs and pterosaurs. There were no flying vertebrates, although there was a family of gliding reptiles by the end of the period.

Also appearing late in the Permian were the first synodonts, which would evolve into mammals during the next period. Permian synapsids (the group that would later include mammals) thrived and included some large members, such as Dimetrodon. Their special adaptations enabled them to flourish in the drier climate, and they grew to dominate the vertebrates.

In the Permian sea, life was everywhere. You might have found mollusks, starfish, sea dollars, sea urchins and sea cucumbers if you went swimming, or animals very much like these modern versions. But as stated earlier, most of the marine life went extinct during the last days of this period. Nothing was said about the sharks or fish that were so prevalent in the previous period.

Could we live here? Plenty of plants are growing, at least, where it wasn't a desert, so maybe we could grow crops. Could we domesticate some of the herbivore sail-backed lizards? Would we want to? They're lizards, so they wouldn't give any milk. I have no idea how big their eggs might be, so that might be a reason to domesticate them. Okay, we'll leave some of us here to colonize the Permian, and the rest of us will go on to see what comes next.

 

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

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

https://en.wikipedia.org/wiki/Cimmeria_(continent)

Permian Period Part 1

 The Permian Period is the last period of the Paleozoic Era, and it spans the 47 million years from 298.9 million years ago to 251.9 million years ago.

The Permian witnessed the diversification of two groups, the mammals (and all creatures more closely related to mammals than to reptiles and birds) and the reptiles. But I'm going to look at the conditions existing on the Earth at the time before I consider the animals that populated it.

At the time, the world was dominated by the supercontinent Pangaea, which formed when Euramerica and what was left of Gondwana collided during the Carboniferous. There was a smaller continent that lay to the northeast of Pangaea called Angara. There were also some small islands east of Pangaea called Cathaysia. Of course, with most of the land mass gathered into one supercontinent, the rest of the globe was ocean. The superocean of the time was the Panthalassa. Pangaea straddled the equator and reached for the poles (but didn't necessarily get there). This, of course, had an effect on the ocean currents of the time.

Early in this time period, Cimmeria—a string of microcontinental islands—tore off from the Gondwana area in the Southern Hemisphere and during the course of the period, moved up to join the Eurasian part of Pangaea in the Northern Hemisphere. Cimmeria included parts of today's Turkey, Iran, Afghanistan, Tibet and the Malay Peninsula. The Central Pangean Mountains, which began forming due to the collision of Laurasia and Gondwana during the Carboniferous Period, reached their maximum height shortly after the beginning of the Permian, and would have been comparable to the present Himalayas.

The Carboniferous rainforest collapse left behind vast regions of desert stretching over the continental interior. From approximately 262 million years ago to 259 million years ago, a series of volcanic erruptions in what is now China (was then part of Pangaea) led the way to an extinction event. This was compounded when a similar series of volcanic activity over a wide swath of Siberia (then located in Angara) continued to change the atmosphere. This mass extinction event ended the Permian Period, and started the next period. It was the largest mass extinction in Earth's history, with nearly 81% of marine species and 70% of terrestrial species dying. On land, it took 30 million years into the next time period for the ecosystems to recover.

Sea levels were mostly stable during the Permian, at several tens of meters (yards) above the present level. There was a sharp drop at one point, producing the lowest sea level of the entire Palaeozoic Era, roughly the same as today's level.

At the start of the Permian, the Earth was still in an icehouse. Around 323 million years ago, glaciers began to form around the South Pole, which would eventually cover a vast area of the southern Amazon Basin, Southern Africa, Australia and Antarctica. The coldest period was around 293 million years ago. By 285 million years ago, temperatures warmed, and a great deal of the ice retreated, although some glaciers remained. The Permian was cool compared to other time periods, at least until those volcanoes started pouring CO2 (a greenhouse gas) into the atmosphere.

It sounds like the Permian had a lot of diverse climates and ecosystems, right? So as long as we stayed away from that awful desert, we should be able to find a nice place to live. So let's take a look at the neighbors we'd have in the next blog.

 

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

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

https://en.wikipedia.org/wiki/Cimmeria_(continent)

Carboniferous Period

 The Carboniferous Period spanned 358.9 million years ago to 298.9 million years ago. On a time table, it sits behind the Devonian Period and before the Permian Period.

In the Early Carboniferous Period, average global temperatures were approximately 68 F (20 C). During the Middle Carboniferous, they dropped to about 54 F (12 C). Carbon dioxide levels fell during the period from roughly 8 times today's level at the beginning to about the same as today's level at the end. Lack of growth rings of fossilized trees suggest a lack of seasons, or a tropical climate. Glaciations in Gondwana were triggered by its southward movement, and continued beyond this time period.

Also, there was mountain building as continents collided to form Pangaea. There was a minor extinction event at the end of the period, caused by climate change.

Now, the last we heard, pieces of Gondwana had broken off and were sitting at the equator or slightly north, while the rest of Gondwana drifted south to the south pole.

During the Carboniferous Period, the land was covered by vast forests, which would eventually become the coal beds characteristic of this period's stratigraphy. Some of the Early Carboniferous land plants were very similar to those of the Late Devonian, but new groups also appeared. The main plants of the early period were horse-tails, scrambling plants, club mosses, scale trees, and ferns. The club mosses of this period are cousins to today's tiny club-moss, but not ancestors; and they had trunks 30 meters high and up to 1.5 meter in diameter. Another type of large tree was ancestor of today's ferns. These continued throughout the period, but late in the period, they were joined by cycads (a new form of 'seed fern') and plants related to conifers.

At least one tall plant (6 to over 30 meters tall) was related to cycads (often mistaken for palm trees) and conifers and are thought to have lived in swamps. True conifer trees appeared later in the period and preferred higher, drier ground.

During this period, animals and bacteria had great difficulty processing the lignin and cellulose that made up the gigantic trees. After the trees died, they piled up on the ground, occasionally becoming part of long-running wildfires after a lightning strike. Others very slowly degraded into coal. White rot fungus was the first living creature that could process these trees and break them down.

Animal life was well established by now. Amphibians were diverse and common by the middle of the period, the dominant type of land vertebrates. Some were as long as 6 meters, but most were probably about 6 in (15 cm) in length. Some were aquatic and lived in rivers, while others may have been semi-aquatic. One branch of amphibians would eventually evolve into the first solely terrestrial vertebrates. The cooling climate slowed the evolution of amphibians, who could not survive as well in the new conditions.

Insects, spiders, crustaceans, and others were also very common, and many were much larger than those of today. The atmospheric content of oxygen reached its highest level in Earth's history—35% compared to today's 21%—which allowed the land invertebrates to get so large. There was a millipede-like creature that grew to 8.5 ft (2.6 m) long. Startling to come across, but if you could kill it, there should be some meat on all those legs. This was the largest known land invertebrate of all time. Among the insects, there were the griffinflies, which included a dragonfly-like insect with a wingspan of 30 in (75 cm). This was the largest flying insect ever to roam the planet. Many other insects flew and crawled about, including cockroach ancestors.

Reptiles, however, prospered due to specific adaptations, such as the amniote egg, which allowed the laying of eggs in a dry environment. Some of the small lizard-like animals gave rise to many descendants, including reptiles, birds and mammals.

I wanted to include a statement about the marine animals of the time, but that section of the article was mostly full of names and little else. I did gather than sponges were fairly prolific and diverse. Also sharks evolved into a multitude of shapes and sizes. Although sharks were mostly sea creatures, there was one type that would sometimes visit swamps. At least one marine fish explored river outlets, and fresh-water fish were common in rivers.

During the latter half of this period, there were glaciations, which meant low sea levels. The cooling and drying of the climate led to a minor extinction event at the end of the period. The tropical rainforest fragmented and then was devastated by climate change.

 

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