Fig. 4
From: From Land to Water: the Origin of Whales, Dolphins, and Porpoises
Astragali (bone of the ankle) of the raoellid Indohyus (RR 224), the pakicetid Pakicetus (H-GSP 98148), a modern pig (3/84), and a modern deer (2/93). This shape of the astragalus, with a proximal trochlea (hinge joint) as well as distal trochlea, only occurs in even-toed ungulates (artiodactyls)