Pteraspis

Pteraspis is an extinct genus of jawless fish that lived during the Silurian and Devonian periods. These early vertebrates are characterized by their distinctive bony armor, which covered their heads and thoraxes. The name Pteraspis itself means "wing shield," referring to the large, wing-like pectoral plates that likely aided in stability or maneuverability in the water.

Fossil evidence suggests that Pteraspis inhabited freshwater and possibly estuarine environments. Their diet is thought to have consisted of small invertebrates and organic matter, which they likely sifted from the sediment using their mouths. Unlike modern fish, Pteraspis lacked paired fins, relying on a caudal fin for propulsion and their pectoral plates for some degree of control.

The armor of Pteraspis was composed of thin, bony plates fused together, forming a solid shield. This protective covering may have defended them against predators or provided structural support. The arrangement and shape of these plates varied among different species within the Pteraspis genus, offering clues about their evolutionary relationships and adaptations to their specific ecological niches. The study of Pteraspis provides valuable insights into the early evolution of vertebrates and the development of bony skeletons and armor.