Figure 7.

Ankle evolution within Archosauriformes. (A) Evolution of different ankle morphologies for both the Nesbitt⁶¹ (foreground) and Ezcurra³⁶ (shadowed) topologies. The suchian tarsus evolved once and is ancestral to phytosaurs, pseudosuchians and avemetatarsalians in either tree. The nomenclature of the ankle morphotypes follows Sullivan⁴⁵. (B) Illustrations of ankle morphologies for exemplary taxa of the displayed groups. (C) Uncertain timing of the transition between a rotary and parasagittal ankle joint within archosaurs. Phytosaurs could either represent a transitional phase⁶¹ (in the foreground) or either a reversal of the joint function or a parasagittal ankle joint evolved twice independently³⁶ (shadowed). The ankle bones of the taxa as in Fig. 1 are depicted.