Lobe finned fish themselves are not a strictly independent phylogenic assemblage. All are sarcopterygians, the subclass encompassing both Dipnoi and Crossopterygians, and examples of lobe fins are found from both of these groups. The lungfish above is a member of the Dipnoi lobe fins.
It is generally believed that tetrapods arose from the extinct Rhipidistian lobe finned fish. The living examples of lobe fins today are strictly lungfish from the Dipnoi side. They are, however, still useful in research into what the behavoir of their extinct counterparts might have been.
Lobe-fins are characterised as being supported by a set of articulated bones attached to the shoulder and pelvic bones. These are moved by muscles that stretch out from the body into the characteristic stumpy 'lobe-like' fins.
Some general characteristics of lobe fins: