The appendages of cockroaches and turtles are modified for creeping movements, but their internal structures are completely different from each other's. What could be the possible interpretation for this similarity? The appendages of cockroaches and turtles are homologous structures, and they have evolved from two different ancestors. The appendages of cockroaches and turtles are homologous structures, and they have evolved from a common ancestor. The appendages of cockroaches and turtles are analogous structures, and they have evolved from two different ancestors.