Which features of a brown trout represent the generalized protacanthopterygian body plan?

The brown trout (Salmo trutta) serves as a standard model for the generalized protacanthopterygian body plan, exhibiting nonspecialized morphology that allows it to thrive in diverse ecological niches. Its features representing this generalized plan include:1

• Streamlined Symmetry: The body and fins are streamlined and symmetrical, facilitating efficient movement.1
• Scales: The body is covered with small, smooth cycloid scales.1
• Fin Structure: The fins are composed of soft supporting rays rather than spines.1
• Fin Placement: The dorsal fin is positioned midway along the back. The paired pectoral fins are located directly behind the head, while the paired pelvic fins are situated directly beneath the dorsal fin. A single anal fin is located beneath the adipose fin.1
• Adipose Fin: A small, fleshy adipose fin is present between the dorsal fin and the tail, a characteristic feature of many members of this group.12
• Caudal Fin: The well-developed tail (caudal fin) indicates powerful swimming capabilities.1