The ankle of "Westlothiana", as well as that of most other "reptiliomorphs", is intermediate between these two conditions. Smithson (1989) reported that "Lizzie" had nine ankle bones, including an astragalus and calcaneum, and that the third and fourth centrales were already fused or lost. Yet he also noted that centrales one and two (which formed the navicular bone) were unfused. Smithson "et al." (1993) later claimed that there were ten bones, arguing that the components of the astragalus were not completely fused, with the intermedium and tibiale still separate. Piñeiro, Demarco, & Meneghel (2016) could not determine which of these two interpretations were superior, but did note that the largest bone more closely resembled a fused astragalus rather than an unfused intermedium.