Figure 1.

Himalayacetus subathuensis type specimen compared with an earlier Asian mesonychid and a later Asian archaeocete. All are left dentaries shown in medial view. (a) Sinonyx jiashanensis type (6), late Paleocene, with incisor I_1–3, canine C₁, premolar P_1–4, and molar M_1–3 (China; Institute of Vertebrate Palaeontology and Palaeoanthropology IVPP 10760). (b) H. subathuensis type, early Eocene, with M_2–3 (India; Roorkee University RUSB 2003). (c) Representative middle Eocene archaeocete with P_3–4 and M_1–3 (Pakistan; Geological Survey of Pakistan–University of Michigan GSP-UM 3062, drawing reversed from right side). Note similarities in overall size and rounded molar profiles, suggesting similar trophic adaptation. H. subathuensis retains a small mandibular canal (mc) like that of earlier mesonychids, contrasting with the larger mandibular canal of Ambulocetus and all postpakicetid archaeocetes; a small mandibular canal precludes whale-like hearing in water (3).