张和兽（Zhangheotherium）是目前唯一保存完整骨架的对齿兽类。其西列特征表明它属于兽科（Spalacotheriidae），该科为原始兽类中主要繁衍于北方大陆中生代后期一个咀嚼方式以上下日齿对咬为主的单系类群。张和兽骨骼形态显示其前肢姿势处于外展趴卧（sprawling）与内收直立（parasagittal）之间，兼有树上和地面活动的能力，是原始兽类中趋于以地面活动为主的成员。附录列举了哺乳类的主要齿列和骨骼性状序列及分布矩阵。 Zhangheotherium is the only pachydermous with complete skeleton preserved. Its Seleucus feature indicates that it belongs to the genus Spalacotheriidae, which is a monophyletic group of the primitive mammals that mainly breeds in the late Mesozoic Mesozoic in the northern half of the continent with a chewing pattern of upper and lower teeth. Zhang and animal skeletons show that their forelimb posture is between sprawling and parasagittal, with both tree and ground activity, which is mainly dominated by ground activities in primitive mammals member. The appendix lists the major dentition and skeletal traits and distribution matrices in mammals.