Early cretaceous mammals of Western Siberia: 3. Zhangheotheriidae

New material of Kiyatherium cardiodens Maschenko, Lopatin et Voronkevich, 2002 from the Early Cretaceous Shestakovo 3 locality (Kemerovo Region, Western Siberia) suggest that this taxon belongs to symmetrodont mammals of the family Zhangheotheriidae. Kiyatherium has relatively long and narrow upper and lower molars, with large trigon and trigonid angles (triangularity is approximately as pronounced as in Tinodontidae); a wide and deep Meckel’s groove; a reduced and strongly posteriorly inclined coronoid process of the lower jaw; a very deep posterior mandibular incisure; a strong pterygoid crest; and a small pterygoid fossa. The evolutionary level of dental and mandibular morphology suggests that Kiatherium occupies a basal position in the family. The holotype of K. cardiodens shows replacement of the first molar, which is a unique case among Trechnotheria.