Heteroptychodus

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Heteroptychodus is an extinct genus of hybodont, a type of ancient cartilaginous fish related to sharks. It lived in Asia during the Early Cretaceous period. The teeth were low, rounded, and ridged, adapted for crushing hard prey. Species include H. chuvalovi, H. kokutensis, and H. Steinmanni. Fossils have been found in Japan, Mongolia, Malaysia, Thailand, southern China, and possibly Kyrgyzstan, mostly from freshwater deposits.