Morphological comparison between the extant Polypterus and the Devonian Osteolepis 插畫檔

This illustration presents a comparative study of two ganoid fishes, highlighting the evolutionary continuity of specific anatomical features. The upper figure depicts a modern species, characterized by an elongated body covered in thick, rhomboidal scales and a unique dorsal fin composed of a series of separate finlets. The lower figure shows an ancient lobe-finned fish from the Devonian period, which possesses a similar armor of heavy, bony scales and a robust head-shield. Both specimens are illustrated to emphasize the structure of the pectoral fins, where the fin-rays are organized around a fleshy central lobe. This shared limb-like architecture in the ancient specimen represents a critical evolutionary link toward the development of terrestrial vertebrates, demonstrating the transition from simple aquatic fins to more complex skeletal supports.