Abstract: Two acrodont iguanians from the middle Eocene Huadian Formation, Jilin Province, China, highlight the diversity of Acrodonta early in the Tertiary. The first is characterized by a high number (six) of anterior pleurodont tooth loci and by unicuspid, labiolingually compressed cheek teeth. These teeth, however, show no special similarity to those of major acrodontan clades in which the accessory cusps are absent (e.g., Hydrosaurus, Agaminae). Its relationships are poorly constrained. The dentition of the second taxon is similar to that of a number of living tricuspid agamids (viz., Leiolepis and Draconinae) and species of the fossil taxon Tinosaurus; one osteological feature suggests it may be related to a clade including Agaminae, Hydrosaurinae, Draconinae and Amphibolurinae, but more numerous and complete specimens are required before conclusions are drawn. A comparative examination of living agamids demonstrates that tricuspid teeth similar to those of Tinosaurus spp.are probably characteristic of some 200 living species in Leiolepis and Draconinae.Tinosaurus is inadequately diagnosed with respect to these clades. Because Acrodonta is thought to have been diversifying in the early Cenozoic, fossils from eastern Asiahave great potential to elucidate the evolutionary history of the clade, particularly in combination with molecular-genetic methods. However, the multiplication of new taxon names based only on jaw fragments brings us no closer to this goal.Considerable effort must first be dedicated to the collection and study of modern comparative skeletal material.

摘要： 中国吉林省中始新世桦甸组的两种端生齿鬣蜥类化石突显出端生齿类(Acrodonta)在第三纪早期的分化。第一种化石的特征为具有多个(6个)前侧生齿位及单尖且侧扁的颊齿。其牙齿与牙齿缺失附尖的主要端生齿类(如鬣蜥亚科Agaminae的海蜥属Hydrosaurus)无特别相似之处，其亲缘关系也并不清楚。第二种的牙齿与很多现生有三尖齿的鬣蜥类(即蜡皮蜥属Leiolepis和飞蜥亚科Draconinae)以及化石响蜥属的许多种相似；一个骨骼特征显示其可能与包括鬣蜥亚科、海蜥属、飞蜥亚科和须鬣蜥亚科(Amphibolurinae)的支系有关，但尚需更多更完整的标本以做结论。与现生鬣蜥类的比较研究表明，与响蜥属牙齿相似的三尖型齿很可能是蜡皮蜥属及飞蜥亚科中大约200个现生种的典型特征。相对于这些支系，响蜥属的鉴定特征并不充分。由于端生齿类的分化被认为始于新生代早期，因而东亚的化石材料很可能有助于阐明这一支系的演化历史，尤其是结合分子遗传学的研究方法。然而仅基于破碎颌骨材料的新分类单元名称的成倍增加并不能使我们更接近这一目标，尽力采集标本并研究可对比的现生骨骼材料应是第一位的。