Is the coelacanth a ‘living fossil’?
Definitely not if you think that means these fish have not evolved since the dinosaur days.
These sketches show the huge variety of body shapes and sizes (in meters) that evolved among the coelacanths. Some had a short, round body, some had a long, slender body, some were eel-like, others resembled trout or even piranha, Casane and Laurenti point out. You can see how Latimeria, the lone surviving coelacanth lineage, attained double the body length of its closest relative, the extinct Macropoma, and also developed a very different body shape.
Source: Why coelacanths are not ‘living fossils’ A review of molecular and morphological data, by Didier Casane and Patrick Laurenti, Bioessays (2013)