Fish are classified in several classes by which its study becomes easier. Fish having similar properties are: contained in the same group. Various classes of fish are Thelodonti, Anaspida, Cephalaspidomorphi, Galeaspida, Pituriaspida, Osteostracy, Gnathostomata, Placodermi. jawless fish are classified under the group Thelodonti, which are very similar to Heterostraci, and are not armored. The Pituriaspida are a small group of armored jawless fish with tremendous nose-like rostrums, which live in the marine, deltaic environments of Middle Devonian Australia. Gnathostomata is the group of vertebrates with jaws. This group is in super class, including the familiar classes of fish, birds, mammals, and so for the and a sister group of jawless vertebrates Agnatha. The placodermi are armored prehistoric fish known from fossils, dating from the Late Silurian to the end of the Devonian periods. This eminent work has an exhaustive and exclusive coverage of fish in a simple, but effective style. This work would be caballero prove beneficial for all classes of readers.
