The search for or study of Ichthyes (Fish) whose existence or survival is disputed or unsubstantiated.
Osteichthyes is a very broad umbrella term. It separates into three other groups. The Agnatha Ichthyes, the Chondrichthyes and the True Osteichthyes. The Agnatha Ichthyes are jawless and are quite primitive. This group includes Lampreys and Hagfishes. The second group, the Chondrichthyes are your cartilaginous fish. This group contains Sharks, Chimaeras, Sawfishes, Skates and Rays. Finally the last group are the bony fish. They are then divided into two more groups. They are the Sarcopterygii (Lobe-Finned Fish) and the Actinopterygii (Ray-Finned Fish). The Sarcopterygii include Coelacanths, Lungfish, and extinct advanced fish like Tiktaalik. All the rest of the fishes are Actinopterygii. But they are sub-divided even more to cartilaginous fish showing some forms of ossification (Chondrostei) and the fully developed ossified fish (Neopterygii). The Chondrostei contains Sturgeons, Paddlefishes, Reedfishes and Bichirs. Finally the Neopterygii contains the rest.
