Pantodonta was one of the first groups of eutherians to evolve at the beginning of Cenozoic era,including the largest herbivores at that time.Pantodonta shows considerable diversity during the Paleocene and Eocene,with most of the species having been discovered in Asia and North America.Here,we report on a new pantodont,represented by lower jaws with well-preserved dentition,discovered from the Middle Paleocene Nongshan Formation of the Nanxiong Basin,Guangdong Province,China.Its unique dental and mandibular characteristics distinguish it well from any known Asian pantodont,but are quite consistent with North American taxa,especially Pantolambda and Titanoides.The new specimen is identified as Nanxiongilambda yei gen.et sp.nov.,characterized by the combination of the following morphological features:thick and robust mandible with a conspicuous anteroexternal flange,high positioned condyloid process,posteriorly protruding angular process,robust but not elongated lower canines,double-rooted p1,small but distinct talonids on posterior lower premolars,talonids nearly as wide as trigonids on lower molars,and m3 with a well-developed hypoconulid and a distinct entoconid.The new discovery marks the first record of a pantolambdid pantodont outside of North America,suggesting a broader geographical distribution and intercontinental dispersal of this clade during the Paleocene.Considering the more primitive Pantolambda only found from Torrejonian to early Tiffanian NALMA(equivalent to middle-late Shanghuan to early Nongshanian ALMA),which is slightly earlier than Nanxiongilambda(early Nongshanian ALMA),pantolambdids have likely undergone a particular wave of migration from North America to Asia during the Early-Middle Paleocene.Previous researches have suggested that pantodonts had dispersed only from Asia to North America during the Early Paleocene,but our new specimen indicates the biotic dispersal may have occurred in the opposite direction.The new specimen also contributes to the renewal of the evolutionary history of
甘肃临夏盆地因巨厚的新生代陆相沉积和大量的哺乳动物化石而闻名于世,其中奇蹄目化石因在生物地层和古环境研究方面有重要意义而备受关注。本文描述了甘肃省临夏盆地发现的3种爪兽和一种安琪马化石。椒子沟地点的Schizotherium ordosium进一步证实椒子沟组的时代当属晚渐新世;老沟地点和上沟地点的Schizotheriinae gen. et sp. indet.和Anisodon sp.表明在中中新世全球气候适宜期,我国北方爪兽类的生物多样性是比较高的;上沟地点的Anchitherium gobiense是通古尔期的代表物种之一,它的存在说明上沟化石地点的时代为中中新世晚期。爪兽类和安琪马都是林栖型的动物,指示了临夏盆地晚渐新世以疏林环境为主,中中新世晚期温湿森林更加普遍。
