Ganoid fish are a group of ancient fish characterized by their unique scales, which are made of a hard, bony material called ganoid. These scales are typically diamond-shaped and provide protection. Ganoid fish include species such as sturgeons and gars, which are often found in freshwater environments. These fish have a streamlined body and a distinctive structure in their skeletons, which can include a mix of cartilage and bone. Ganoid fish are known for their ability to thrive in various habitats, and they play important roles in their ecosystems as both predators and prey.