Crurotarsus

Crurotarsus refers to a specific ankle joint structure found in archosaurian reptiles, including crocodilians, birds, and extinct dinosaurs. This term describes a mesotarsal ankle where the astragalus and calcaneum are fused, and the articulation between them allows for a hinge-like motion. The tibiotarsus and the tarsals articulate at a single joint. This type of ankle structure is in contrast to the crurotarsal ankle found in some other archosaurs, where the astragalus and calcaneum are not fused, and the articulation allows for more complex rotational movements. The crurotarsal ankle is a key characteristic used in the classification and understanding of the evolutionary relationships between different groups of archosaurs. It is considered a primitive feature within Archosauria. The presence or absence of this specific ankle morphology has been instrumental in paleontological research for differentiating dinosaur clades and understanding their locomotion. The evolution of the crurotarsus played a role in the diversity and success of these reptilian groups throughout the Mesozoic Era.