Fig. 1

Morphology of calcaneus (a, b) and astragalus (c, d) in Tamquammys robustus (A, C; IVPP V24136.1 and V24136.4 respectively) and Tamquammys wilsoni (B, D, IVPP V V24137.2 and V24137.4 respectively; mirror images) from Nuhetingboerhe, Nei Mongol, China. Bones shown in dorsal (A1, B1, C2, D2), medial (A2, B2, C3, D3), lateral (A3, B3, C4, D4), and plantar (D1, C1) views. Abbreviations (yellow denotes articular surfaces, white other major anatomical structures, and black, grooves for major tendons): af, astragalofibular articulation surface; ah, astragalar head; anas, astragalonavicular articulation surface; atid, distal astragalotibial articulation surface (aff, astragalar groove for tendon of flexor fibularis muscle sensu Chester et al. 2015); cacu, calcaneocuboid articulation facet; cb, calcaneal body; cff, calcaneal groove for tendon of flexor fibularis muscle; cnl, calcaneonavicular ligament; ct, calcaneal tuber; dhp, dorsal heel process; dpt, distal plantar tubercle; ef, ectal facet (on both calcaneus and astragalus); gtpb, grove for tendon of peroneus brevis muscle; gtpl, grove for tendon of peroneus longus muscle; lc, lateral astragalar crest; lpct, lateral process of calcaneal tuber; ltf, lateral tibial facet; mc, medial crest of astragalar trochlea; mpct, medial process of calcaneal tuber; ne, astragalar neck; php, plantar heel process; pp., peroneal process; su, sustentaculum tali with sustentaculum facet; suf, sustentacular facet of astragalus; suh, sustentacular hinge; tt, trochlea tali