The multiscale architecture of tessellated cartilage and its relation to function

When describing the architecture and ultrastructure of animal skeletons, introductory biology, anatomy and histology textbooks typically focus on the few bone and cartilage types prevalent in humans. In reality, cartilage and bone are far more diverse in the animal kingdom, particularly within fishes (Chondrichthyes and Actinopterygii), where cartilage and bone types are characterized by features that are anomalous or even pathological in human skeletons. This review discusses the curious and complex architectures of shark and ray tessellated cartilage, highlighting similarities and differences with their mammalian skeletal tissue counterparts. By synthesizing older anatomical literature with recent high-resolution structural and materials characterization work, this review frames emerging pictures of form–function relationships in this tissue and of the evolution and true diversity of cartilage and bone.