ABSTRACT Sparassodont metatherians were the dominant terrestrial mammalian predators during South America's long Cenozoic isolation. This group's early fossil record is very poor, however, particularly for the late Eocene and early Oligocene. Here, we describe a new sparassodont, Chlorocyon phantasma, gen. et sp. nov., based on a specimen from Los Helados, a new locality within the Abanico Formation of the Andean Main Range of central Chile. New 40Ar/39Ar dates at Los Helados bracketing the fossil-bearing level constrain the age of this specimen to 37–36 Ma (late Eocene), indicating that this new taxon likely pertains to the Mustersan South American Land Mammal “Age.” Chlorocyon is the first Paleogene sparassodont reported from Chile and the first sparassodont described from the Abanico Formation. Distinctive features, including a p3 with an anterior edge that is more curved than the posterior edge and the lack of a hypoconulid on m4, suggest that Chlorocyon is a borhyaenoid closely related to Pharsophorus or Plesiofelis, although much smaller. Chlorocyon represents a welcome addition to the sparse record of late Eocene sparassodonts and indicates that the diversity of non-proborhyaenid borhyaenoids prior to the late Oligocene was greater than previously thought.

中文翻译：

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Chlorocyon phantasma，一种来自智利中部安第斯主要山脉洛斯赫拉多斯地区的晚始新世 Borhyaenoid（哺乳动物：Metatheria：Sparassodonta）

摘要 在南美洲新生代的长期隔离期间，Sparassodont metatherians 是主要的陆生哺乳动物捕食者。然而，该组的早期化石记录非常差，尤其是始新世晚期和渐新世早期。在这里，我们描述了一种新的 sprassodont，Chlorocyon phantasma，gen。等 sp. 11 月，基于来自洛斯赫拉多斯的标本，这是智利中部安第斯主山脉阿巴尼科组内的一个新地点。Los Helados 的新 40Ar/39Ar 日期将含化石水平括起来，将这个标本的年龄限制在 37-36 Ma（始新世晚期），表明这个新分类群可能属于 Mustersan 南美陆地哺乳动物“年龄”。Chlorocyon 是第一个从智利报道的古近纪 sparassodont，也是从 Abanico 组描述的第一个 sprassodont。特色鲜明，包括前缘比后缘更弯曲的 p3 以及 m4 上没有下锥体，表明 Chlorocyon 是一种与 Pharsophorus 或 Plesiofelis 密切相关的 borhyaenoid，尽管要小得多。Chlorocyon 代表了晚始新世 sprassodonts 的稀疏记录的一个受欢迎的补充，并表明晚渐新世之前的非 proborhyaenid borhyaenoids 的多样性比以前认为的要大。