My creature is part of one of the many eras of the past. My creature was part of the Palezoic Era (Pa-le-zo-ic). This era lasted 570 million years ago to 240 million years ago. This era also was the era of the introduction of half land animals or lizards.My exact era of the six subdivisions of the Palezoic Era is the Carboniferous Period. This era is the second youngest of all six. My animal or organism is the crassigyrinus (crass-i-ji-rinus-us) or in its scientific name Crassigyrinus scoticus. Now, the Carboniferous Period also had two branches the Mississippi and the Pennsylvanian Period. The crassigyrinus is from the Pennsylvanian Period. This era lasted 320-286 million years ago. This period was also the time when many scientists say that the Earth was rich with carbon dioxide.There were many, many plants in swamps at the time. And at the time the whole land was made up of swamps because the land was barely out of sea level. The plants later turned into large coal deposits. That is why it is called the Carboniferous Era.
The crassigyrinus could grow up to 7 feet and basically looked like a huge tadpole. It had a huge, heavy, muscular jaw and the bottom half is the whole head really! His jaw was lined with a row of very sharp teeth to eat the fish he caught. The lower jaw is deep and scientists have been fascinated along time how his head is formed. It had a tough, long sausage-like body for swimming on the bottom of the swamps or ponds. This is a very good adaptation because the deeper you go the more water pressure pushes down. It had a similar deep fish-like tail. It used its very tiny hands to crawl on land when it wanted to. It was could to walk on land because air in the water is not as concentrated as the air above.
The crassigyrinus was actually a development of the "Lung-fish". This lung fish dates back about 400 million years ago. The lung fish is believed to be the first fish to breathe out of the water.The lung-fish was more able to survive because other fish couldn't go on land and travel more but the lung-fish could. The way it can breathe is by a lung organ called the bladder or the gas bladder. This was a good adaptation because the air above is more concentrated than the air below in the water.
The reason that it may be extinct today and didn't make it to the Mesozoic (Me-so-zo-ic) Era is because of the earth changing. After the first land animal (dinosaurs) appeared about 245 million years ago the Earth and climate changed (dinosaurs died because of comets that fell to Earth and crashed into the Earth). It was adapted to the large coal deposits and the plants. The Earth shifts on crust plates called tectonic plates and when they move into each other they cause volcanoes, and earthquakes. Back then the Earth was moving around on the tectonic plates and the Earth changed. Some swamps might have disappeared or dried. All around was mostly land except for the big oceans in which the crassigyrinus couldn't get to because of the long travel. It wasn't adapted to the new species of marine life and the deep oceans. Unlike lizards such as: monitors, Komodo Dragons, etc., they can hold water and don't have to have water all the time. Crassigyrinus did.
Clack, Jennifer, Crassigyrinus scoticus, http://ag.arizona.edu/ENTO/tree/eukaryotes/animals/chordata/crassigyrinus/, c1998.
Hieb, Monte, and Hieb, Harrison, Carboniferous Period and West Virginia 300 million years ago, cEducational Series ED 3A, 1978.
By: Carolyn C.
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