tarsi

Tarsi are the distal parts of limbs in various animals. In vertebrates, the tarsus (plural tarsi) refers to the cluster of ankle and midfoot bones that connect the lower leg to the metatarsals. It consists of seven bones: the talus, calcaneus, navicular, cuboid, and the three cuneiforms (medial, intermediate, and lateral). The tarsus forms the ankle joint with the tibia and fibula (the talocrural joint) and the subtalar joint with the calcaneus, enabling movements such as plantarflexion, dorsiflexion, inversion, and eversion. It also distributes body weight across the foot and contributes to the arches that absorb shock and adapt to varying surfaces. Clinically, problems affecting the tarsus include tarsal coalitions, talipes (clubfoot), pes planus (flatfoot), and midfoot arthritis.

In arthropods, especially insects and arachnids, the tarsus is the final segment of the leg. In insects, it is subdivided into one or more tarsomeres and typically ends with claws or pads that aid in locomotion and grasping. The number of tarsomeres and the presence of claws or adhesive structures are useful taxonomic characters. In spiders, scorpions, and related groups, the tarsus is likewise the distal leg segment and often bears claws, scopulae, or tactile pads.

Overall, the term tarsi encompasses both the anatomical hindfoot structure in vertebrates and the distal leg segment in many invertebrates, reflecting diverse functional adaptations across taxa.