ABSTRACT Understanding of the Asian early Paleogene avifauna is limited relative to that of North American and European avifauna of the same period. While major patterns of mammalian faunal exchange among these three regions across the Paleocene/Eocene boundary have been described, much less is known about the dynamics of bird diversity over the same time interval. Here, we report bird fossils from the earliest Eocene Bumban Member of the Naranbulag Formation in central Mongolia that add to the known record from Asia from just after this boundary. Most of this material, collected by the joint American Museum of Natural History/ Mongolia Academy of Sciences expeditions, is referable to a previously described taxon in Presbyornithidae (Anseriformes). However, five isolated elements are identified as comprising at least four species from at least three other major avian clades. While further inclusive phylogenetic analyses of each of these clades are necessary, the new remains represent possible earliest occurrences in Asia of these clades. The material includes a humerus and a furcula from shorebirds (Pan-Charadriiformes), a quadrate from a stem member of the flamingo-grebe lineage (Pan-Mirandornithes), and a coracoid from a stem galliform (Pangalliformes). We also report a humerus with uncertain phylogenetic affinities but with similarities to core Gruiformes. These new fossils expand our knowledge of the Asian avifauna during this time and have the potential to further inform our understanding of the early biogeography of these clades. The shorebird and flamingo-grebe material indicate that both these lineages were present in Asia by the earliest Eocene. The pan-mirandornithine quadrate provides insight into the early feeding ecology of the flamingo-grebe clade.

中文翻译：

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来自蒙古最早始新世的新鸟类化石

摘要 相对于同时期的北美和欧洲鸟类，对亚洲早期古近纪鸟类的了解是有限的。虽然已经描述了跨越古新世/始新世边界的这三个地区之间哺乳动物动物群系交换的主要模式，但对同一时间间隔内鸟类多样性的动态知之甚少。在这里，我们报告了来自蒙古中部 Naranbulag 组最早始新世 Bumban 成员的鸟类化石，这些化石增加了亚洲从该边界之后的已知记录。这些材料的大部分由美国自然历史博物馆/蒙古科学院联合探险队收集，可参考先前描述的长鸟科（Anseriformes）中的一个分类群。然而，五个孤立的元素被确定为包括来自至少三个其他主要鸟类进化枝的至少四个物种。虽然需要对这些进化枝中的每一个进行进一步的全面系统发育分析，但新的遗骸代表了这些进化枝在亚洲可能最早出现的地方。该材料包括来自滨鸟（Pan-Charadriiformes）的肱骨和分叉，来自火烈鸟 - grebe 谱系（Pan-Mirandornithes）茎成员的方形，以及来自茎鸡形（Pangalliformes）的喙突。我们还报告了一种具有不确定系统发育亲和力但与核心 Gruiformes 相似的肱骨。这些新化石扩大了我们在此期间对亚洲鸟类的了解，并有可能进一步帮助我们了解这些进化枝的早期生物地理学。滨鸟和火烈鸟鸬鹚材料表明，这两个谱系在最早的始新世都存在于亚洲。pan-mirandornithine quadrate 提供了对火烈鸟-grebe 进化枝的早期摄食生态的洞察。