What Are Fish?
Fish live in water, have gills, have a spinal column and appendages that have with no digits (aka fins). The evolution of fish goes back almost 530 million to fish like chordates, with oldest known true fish appearing in the fossil record 480 million years ago. There are about thirty two thousand, known, existing species, that live from high alpine lakes to the intertidal zone to twenty three. A dynamic arcade game for Android Pro Team Ninja-seals. As usual seals decided to eat fish, but in each she disappeared in the magic portal. Cats rushed into a portal for my breakfast, and ended up in another reality in which these same fish want to destroy them.
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The scientific definition of fish is complex and more than a little confusing. So here is a much simplified definition. Fish are: chordates, they have a backbone or notochord (cartilaginous support), live entirely in water, have apparatus to extract oxygen from water (gills), appendages without digits, fins, and are generally ectothermic. There are exceptions to these characteristics, for example some fish can live for long periods of time out of water and some fish, like tuna and large sharks have body temperatures well above the temperature of the surrounding water, but for the most part these characteristics describe fish. Fish can have jaws or be jawless, have scales or skin, drink water or not. A number of organisms we call fish actually are not fish at all. Crayfish are not fish, they do not have a backbone, and their appendages have digits, in this case claws. Likewise shellfish are not fish, this is a marketing term to refer to organisms from the water that have shells. There are about 32,000 species of fish that live in both freshwater and saltwater and from the high mountains lakes to the intertidal zone to 23,000 feet deep in the ocean abyssal plains.
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Where Are Fossil Fish Found?
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Fossil fish can be found on every continent, including Antarctica. There are a number of significant fossil sites around the world.
* The Green River Formation, Wyoming produces large quantities of fossil fish including rays. It is also known for its amazing preservation which results is some of the most stunning fish fossils.
* Solnhofen Limestone, Germany. This site has produced some of the most amazing fossils ever discovered, including the famous Archeopteryx fossil. It also produces fish and other marine animal fossils.
* Some of the most exquisitely preserved, Cretaceous fish in the world come from the limestone deposits near Byblos, Lebanon. The discovery of amazingly preserved fossil fish dates back many centuries. In fact they were first mentioned in writing by Herodotus, over 450 years before the birth of Christ.
* The Crato Formation of Brazil has yielded twenty five species of early Cretaceous fish, many with their stomach contents in tact.
* The Gogo Formation, Australia has produced fifty species of fish, many with soft body preservation of anatomical features as small as nerves.
These are only a few of the most famous fish fossil sites.