Carpals and tarsals

The carpus (wrist) and tarsus (ankle) of land vertebrates primitively had three rows of carpal or tarsal bones. Often, some of these have become lost or fused in evolution. Figure to the right shows locations of rare accessory bones of the foot (presence variable from person to person): 1 = os cuneometatarsal I plantare, 2 = os uncinatum, 3 = os sesamoideum tibialis posterior, 4 = os sesamoideum peroneum, 5 = os cuboideum secundarium, 6 = os trochleare calcanei, 7 = os in sinus tarsi, 8 = os sustentaculum tali, 9 = os talocalcaneale posterius, 10 = os aponeurosis plantaris, 11 = os subcalcaneum, 12 = os sesamoideum tibialis anterior, 13 = os cuneometatarsal I tibiale, 14 = os intermetatarsal I, 15 = os cuneometatarsal II dorsale, 16=os paracuneiforme, 17 = os cuneonaviculare, 18 = os intercuneiforme, 19 = os intermetatarsal IV, 20 = os talonaviculare, 21 = os vesalianum pedis, 22 = os tibiale externum, 23 = os talotibiale dorsale, 24 = os supratalare, 25 = os calcaneus secundarius, 26 = os subtibiale, 27 = os subfibulare, 28 = os retinaculi, 29 = os calcaneus accessorius, 30 = os trigonum, 31 = os supracalcaneum, 32 = os tendinis calcanei.

Comparative vertebrate anatomy

Abbreviations: A, Scaphoid bone; B, Lunate bone; C, Triquetrum; D, Trapezium; E, Trapezoid; F, Capitatum; G, Hamatum; P, Pisiform; Cc, Central carpal; M, Metacarpal; (A-G, Cc, and P are Carpals). 1–5, thumb and digits two to five. R, Radius; U, Ulna. From the classic German encyclopedia Meyers Konversations-Lexikon 1888. Frog four limbs and human foot compared.