Echimyidae is the most widely diversified family among hystricognath rodents, both in the number of species and variety of lifestyles. In the Patagonian Subregion of southern South America, extinct echimyids related to living arboreal species (Echimyini) are recorded up to the middle Miocene, whereas all the known southern fossils since the late Miocene are linked to terrestrial and fossorial lineages currently inhabiting the Chacoan open biome in eastern South America. In this work, we describe a new genus of echimyid rodent, Paralonchothrix gen. nov., from the late Miocene of northwestern Argentina and western Brazil. Its single recognised species, Paralonchothrix ponderosus comb. nov., is represented by two hemimandibles. One of them comes from a level of Loma de Las Tapias Formation, underlying a tuff dated at 7.0 ± 0.9 Ma (Huayquerian age, late Miocene); the other specimen comes from the ‘Araucanense’ of Valle de Santa María (type locality, Huayquerian age, late Miocene). A phylogenetic analysis linked Paralonchothrix to Lonchothrix, both being the sister group to Mesomys. Thereby, for the first time, an echimyid linked to living Amazonian arboreal clades is recognised for the late Miocene of southern South America. Paralonchothrix gen. nov. thus represents an exceptional record that raises the need to review the postulated evolutionary pattern for echimyids recorded at high latitudes since the late Miocene. The new genus provides a minimum age (ca.7 Ma) in the fossil record for the divergence between Mesomys and Lonchothrix. The palaeoenvironmental conditions inferred for the late Miocene in western and northwestern Argentina suggest savanna-type environments, with areas with more closed woodlands in peri-Andean valleys. The record of Paralonchothrix gen. nov. supports the hypothesis that this area would have maintained connections with tropical biomes of northern South America during the late Miocene.

中文翻译：

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副线虫属 11 月，南美洲南部中新世晚期 Echimyini (Rodentia, Octodontoidea) 的首次记录

Echimyidae是hystricognath啮齿动物中最广泛多样化的家庭，无论是物种数量还是生活方式的多样性。在南美洲南部的巴塔哥尼亚次区域，与活树栖物种（Echimyini）相关的已灭绝的棘齿动物被记录到中新世中期，而自中新世晚期以来所有已知的南方化石都与目前居住在查科安开放生物群落的陆地和化石谱系有关在南美洲东部。在这项工作中，我们描述了一种新的棘齿类啮齿动物属，副线虫将军 十一月，来自阿根廷西北部和巴西西部的晚中新世。其单一公认的物种，Paralonchothrix ponderosus梳子。nov.，由两个半下颌骨代表。其中一个来自 Loma de Las Tapias 组，位于 7.0 ± 0.9 Ma（Huayquerian 时代，晚中新世）的凝灰岩之下；另一个标本来自 Valle de Santa María 的“Araucanense”（模式产地，Huayquerian 时代，晚中新世）。系统发育分析副线虫到长丝线虫, 都是姐妹组中体肌. 因此，在南美洲南部的中新世晚期，首次发现了一种与生活在亚马逊地区的树栖进化枝有关的棘齿动物。副线虫将军 十一月 因此代表了一个特殊的记录，它提出了需要审查自中新世晚期以来在高纬度地区记录的棘爪动物的假定进化模式。新属提供了最低年龄（约.7 Ma) 在化石记录中的差异中体肌和长丝线虫. 阿根廷西部和西北部中新世晚期的古环境条件表明存在热带稀树草原型环境，在安第斯山脉附近的山谷中有更多封闭的林地。的记录副线虫将军 十一月 支持该地区在中新世晚期与南美洲北部热带生物群落保持联系的假设。