Five marsupial species are recognized from the Brule Formation at two localities in southwestern North Dakota: Fitterer Ranch and Obritsch Ranch (middle Oligocene; Whitneyan North American Land Mammal Age [NALMA]). The herpetotheriids Herpetotherium fugax Cope, 1873a, Copedelphys superstes new species, and the peradectid Nanodelphys hunti (Cope, 1873b) are represented at both localities. A fourth species is H. sp., cf. H. merriami (Stock and Furlong, 1922), represented by a single specimen from Fitterer Ranch, being limited elsewhere to the later Arikareean NALMA. A fifth species is represented by two isolated lower cheek teeth, interpreted as m1s, from Fitterer Ranch that are unique in lacking a trigonid (only two cusps present) while having a well-developed talonid. These specimens are referred to an indeterminate herpetotheriine species. The new species of Copedelphys is distinct from other species of the genus in that the anterior two lower molars are enlarged relative to the posterior molars. Overall, this new species is more similar in proportions to the latest Eocene (Chadronian) C. titanelix (Matthew, 1903) than the Oligocene (Orellan and Whitneyan) C. stevensoni (Cope, 1873b). This study adds a third and fourth Whitneyan marsupial fauna from the Great Plains region of North America, increases the known diversity of Whitneyan marsupials, and provides further evidence that marsupial diversity during the late Paleogene in North America was relatively stable until the late early Arikareean NALMA.UUID: http://zoobank.org/b8534802-b9ed-4120-baca-fc72917f7d6a

中文翻译：

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北达科他州布鲁尔组（惠特尼延，渐新世）的有袋动物（哺乳动物，Metatheria）

在北达科他州西南部两个地方的布鲁尔组发现了五种有袋动物：Fitterer Ranch 和 Obritsch Ranch（渐新世中期；Whitneyan 北美陆地哺乳动物时代 [NALMA]）。爬虫类Herpetotherium fugax应对，1873a，Copedelphys superstes新物种和peradectidNanodelphys Hunti（Cope，1873b）在两个地方都有代表。第四种是H. sp.，参见H.梅里亚米(Stock and Furlong, 1922)，以来自 Fitterer Ranch 的单个标本为代表，在其他地方仅限于后来的 Arikareean NALMA。第五个物种由两个孤立的下颊齿代表，被解释为来自 Fitterer Ranch 的 m1s，它们的独特之处在于缺乏三角齿（仅存在两个尖齿），同时具有发达的爪齿。这些标本被称为不确定的herpetotheriine 物种。新品种Copedelphys与该属的其他物种的不同之处在于，前两颗下磨牙相对于后磨牙增大。总体而言，这个新物种在比例上与最新的始新世（Chadronian）更为相似C.泰坦利克斯（马修，1903）比渐新世（奥雷兰和惠特尼安）C.史蒂文索尼（科普，1873b）。这项研究增加了来自北美大平原地区的第三种和第四种惠特尼有袋动物群，增加了惠特尼有袋动物的已知多样性，并提供了进一步的证据，表明北美古近纪晚期有袋动物的多样性相对稳定，直到早期的阿里卡里 NALMA .UUID：http://zoobank.org/b8534802-b9ed-4120-baca-fc72917f7d6a