Silurian Period

In Geological time, the Silurian period is the third period of the Paleozoic era. It started 443.8 million years ago and ended 419.2 million years ago, extending from the ending of the Ordovician period to the beginning of the Devonian period. During this period, continents' highlands were much lower and sea level was rising. Sea level rose drastically as the huge glacier from the Late Ordovician ice age melted.  

The immediate changes in climatic conditions permitted many faunal groups to recover from the extinction of Late Ordovician times. Large expanses of different continents became flooded with shallow seas, and mound-type coral reefs were common. Fishes were extensive. Vascular plants began to take over coastal lowlands during this period whereas the continental interiors became infertile. 

When Did the Silurian Period Start?

The Silurian period was the period from the end of the Ordovician period, at about 443.3 million years ago, to the beginning of the Devonian period, 419.2 million years ago. The Silurian period is considered to be the shortest period of the Paleozoic Era.

Silurian Period Significant Events

Life on Land

It was during this period that the first life came about from water and colonized the land. Increased ozone from photosynthetic water plants provided protection from the ultraviolet rays, making the terrestrial environment friendly to those organisms that could prevent desiccation.

First Vascular Plants

The first plant with an internal vascular channel was seen in Silurian period. Plants were not able to transfer food and gases to other parts of the structure, allowing a considerable amount of increase in size.

First Insect

The first insect seen in the Silurian period, was probably the first animal to come out of water.

First Jawed Vertebrates

The first fish with jaws appeared during the Silurian period, providing much better predictability and eventually giving rise to vertebrates known today. 

Silurian Period Climate

The climate was much warmer during the Silurian period. This caused the melting of glaciers and sea levels to rise.  Even though the sea level was rising, there was a place where the land was rising as well. This was due to the mountain building as the continental plates collided. In these places, the seas moved away from the coasts or evaporated from the shallow zones. Plants that had to live in coastal water had to live on land or die.

Fishes Gained Importance During the Silurian Period

Fishes gained much importance during the Silurian period. Most of the fishes were jawless at the beginning of the Silurian period. There were some earlier vertebrates, animals with soft cartilage bones. By the end of the Silurian period, animals with jaws and real bones were swimming in water. These animals soon would rule the seas.

Terrestrial

The most significant progressive development of this period was that of the first true terrestrial ecosystem. 

The first fossil records of vascular plants, that is, land plants with tissue was of those which carries food, occurred during the Silurian period. The vascular plants were simple plants that had not developed individual stems and leaves.

By the middle of the Silurian period, a very simple early terrestrial community with simple plant producers, millipede herbivores, centipede and arachnid carnivores, worm detritivores, and fungal decomposers had developed.

The Mid-Late Silurian terrestrial biota included small plants along with the water's edge and arthropods such as trigonotarbids and myriapods. Fungi, nematodes, and perhaps earthworms were most likely present as well, although they did not leave a fossil record (except for possible fungi).

Did You Know?

• The name Silurian originated from the Celtic from Whales.

• During this period, the sea fluctuated between transgression and regression due to the climatic change and continental buildup.

• The first fossil record of the Vascular plants appeared in the second half of the Silurian period.