Argyrolagus constitutes, both for its craniodental and postcranial anatomy, one of the most notably specialized South American Neogene metatherians. Differentiating it from any other South American mammal, bipedal jumping has been proposed for Argyrolagus, even though this hypothesis was not supported by morphofunctional studies. Here, we describe the postcranium of A. scaglai (from the Pliocene of Argentina), perform a functional analysis, and interpret it against a varied background of locomotor adaptations of extant mammals. The configuration of joints, the degree of development and location of muscular insertions were mainly analyzed, and functional indices were evaluated. This study indicates that Argyrolagus had stabilized glenohumeral and humeroulnar joints, a great development of the arm retractors, flexors-extensors of the digits, pronator, and supinator muscles, low restrictive humeroradial joint, powerful extensor muscles of the hip, knee, and ankle, good development of the iliac muscle, and restrictive hind limb joints. Joint configurations are interpreted to be optimal to resist the impacts during jumping, avoiding dislocation, compatible with digging activity. A compromise between the capacities to dig and manipulate objects is inferred. It is concluded that Argyrolagus had bipedal jumping locomotion as well as good capacity to dig, constituting an astonishing case of convergence with the small bipedal rodents and small Australian macropodids. We suggest that bipedal jumping in Miocene and Pliocene argyrolagids should not be necessarily related to a particular arid environment. Finally, we evaluate the importance of postcranial features to understand the phylogenetic relationships of Argyrolagidae in a comprehensive phylogeny of Metatheria.

中文翻译：

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Argyrolagus (Marsupialia, Argyrolagidae) 的古生物学：南美哺乳动物双足行走的惊人案例

Argyrolagus 的颅牙和颅后解剖结构构成了南美新近纪最显着的特化动物之一。与任何其他南美哺乳动物不同的是，Argyrolagus 提出了双足跳跃，尽管这一假设没有得到形态功能研究的支持。在这里，我们描述了 A. scaglai（来自阿根廷的上新世）的后颅骨，进行了功能分析，并在现存哺乳动物运动适应的不同背景下对其进行了解释。主要分析关节的形态、发育程度和肌肉插入的位置，并评估功能指标。这项研究表明，Argyrolagus 稳定了盂肱关节和肱尺关节，手臂牵开器、手指屈肌-伸肌的巨大发展，旋前肌和旋后肌，低位限制性肱桡关节，强大的髋、膝和踝伸肌，髂肌发育良好，以及限制性后肢关节。关节配置被解释为在跳跃过程中抵抗冲击的最佳方式，避免错位，与挖掘活动兼容。推断出挖掘和操纵物体的能力之间的折衷。结论是，Argyrolagus 具有双足跳跃运动以及良好的挖掘能力，构成了与小型双足啮齿动物和小型澳大利亚巨脚类动物融合的惊人案例。我们建议中新世和上新世 argyrolagids 的双足跳跃不一定与特定的干旱环境有关。最后，