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步林(Bohlin,1951)描述的酒西盆地骟马城(又译为十二马厂)化石(Mimolagus和Anagalopsis)在分类位置与地质年代上长期存在争议。步林认为仅依据这些化石无法确定其年代,只是推测可能为第三纪的早期。后人根据Anagalopsis与内蒙古发现的Anagale对比,认为该化石点大致时代为早渐新世。化石出自哪个层位也有不同的认识。有人认为化石发现在白杨河组下部,也有人认为化石层位属于火烧沟组。鉴于其重要意义,我们于2015年4月赴酒西盆地进行了调查。根据步林的地理位置描述与照片(Bohlin,1940,1951),我们初步确定化石地点应位于骟马城沟内,火烧沟组下部骟马城段。对比内蒙古二连盆地伊尔丁曼哈组新发现的Mimolagus以及晚始新世乌兰戈楚组的Anagale,认为步林描述的化石时代也应为始新世。根据对化石产出层位的重新认识,并对比戴霜等(2005)在火烧沟剖面的磁性地层学资料,推测火烧沟组的时代为中始新世晚期至晚始新世,骟马城化石层位的地质年代大致为中始新世晚期。Mimolagus的生存年代与其近亲Gomphos的差距大大减小,古老的Anagalidae也应该在渐新世之前就已全部灭绝。
The fossils (Mimolagus and Anagalopsis) described by Bohlin (1951) are also controversial over the age of the geologic age. Only that these fossils can not confirm the age of these fossils is only the steppe forest, which is only supposed to be the early Tertiary period. According to Anagalopsis and Anagale found in Inner Mongolia, the descendants believe that the fossil point was generally Oligocene. Fossil from which horizon have different understandings. Some people think that fossils are found in the lower part of the Baiyanghe Formation. Some people think that the fossil beds belong to the Huoxuogou Formation. In view of their significance, we conducted a survey in the Western Xi Basin in April 2015. According to the description and photos of the geographical location of the woods (Bohlin, 1940, 1951), we initially determined that the fossil site should be located in the Shumachenggou and the lower part of the Huoxuogou Formation in the Shumacheng section. A comparison of the newly discovered Mimolagus from the Ildene-Manha Formation in the Erlian Basin, Inner Mongolia, and Anagale from the Late Ulyan Urangogu Formation suggests that the fossil age described by the marlin should also be Eocene. Based on the re-recognition of the fossil output horizon and the comparison of the data of magnetic stratotypes in the HuoGouGou section of Dai et al. (2005), it is speculated that the time of the Huozhangou Formation is from Late Eocene to Late Eocene. The geologic age of fossil beds is roughly in the middle Eocene. The gap between Mimolagus’s life and its close relative, Gomphos, has diminished dramatically. The ancient Anagalidae should also be extinct before Oligocene.