Monday, July 27, 2015

Always learning....

Going to the aquarium in Virginia Beach is a very enjoyable experience. As well as the aquariums full of marine life there are other very interesting exhibits, such as this one showing the Silurian age in Virginia.  You can enlarge the following photos for a clearer look.

The Silurian Period was 443.7 to 416.0 million years ago.  Mind boggling!  It was at a time when the Earth underwent considerable changes that had important repercussions for the environment and life within it.  One result of these changes was the melting of large glacial formations.  This contributed to a substantial rise in the levels of the major seas.  The Silurian witnessed a relative stabilization of the Earth's general climate, ending the previous pattern of erratic climate fluctuations.  

(If you have difficulty reading the writing in the photo below it says: Silurian Virginia was a hot, dry desert surrounded by warm, shallow seas.  Earth's first land dwellers appeared during this period, but most plants and animals still lived in the water.  Trilobites, sea scorpions and other arthropods shared the sea floor with brachiopods, clam-like organisms that were the most common shelled animals.  Above the bottom, bony-armored fishes and squid relatives cruised in search of prey.  On land, spiders, centipedes and worms lived among fungi and simple plants.) 

Coral reefs made their first appearance during this time, and the Silurian was also a remarkable time in the evolution of fishes.  Not only does this time period mark the wide and rapid spread of jawless fish, but also the highly significant appearances of both the first known freshwater fish as well as the first fish with jaws.  It is also at this time that our first good evidence of life on land is preserved, such as relatives of spiders and centipedes, and also the earliest fossils of vascular plants.

The Silurian is a time when many biologically significant events occurred.  In the oceans there was a widespread radiation of crinoids, a continued proliferation and expansion of the brachiopods, and the oldest known fossils of coral reefs.  As mentioned earlier this time period also marks the wide and rapid spread of jawless fish, along with the important appearances of both the first known freshwater fish and the jawed fish.  Other marine fossils commonly found throughout the Silurian record include trilobites, graptolites, conodonts, corals, stromatoporoids and mollusks.

I found the above fascinating information and much more at this website.