Inquiring into the paleoecology of extinct forms is always a challenge, particularly when the taxa under study correspond to derived ecomorphs of ancient and completely extinct clades. In this contribution, the configuration of the masticatory apparatus and associated features of the Neogene pachyrukhines Paedotherium and Tremacyllus are studied in a detailed, mainly qualitative, comparative analysis of 36 specimens. Tooth morphology and the reconstructed muscular configuration of pachyrukhines indicate an important mediolateral component during chewing, and predominant crushing over grinding, as well as anteroposterior movements for the coupling and action of stronger gnawing incisors. These actions are more compatible with hard and brittle or turgid fruit food consumption than specialized folivorous, and particularly grazing, habits. The infraorbital and palatal foramina morphology and other rostral features indicate increased touch sensibility for object recognition and are congruent with the presence of infoldings of the lips protecting the gingiva during gnawing on hard foods. Additionally, there was a morphological gradient between Tremacyllus and P. bonaerense, from high selection of relatively soft and small food items, to specialized hard item consumption and higher resistance for abrasion and masticatory efforts (e.g., in eventual association with digging habits), respectively. Paedotherium typicum presents intermediate characteristics, with incisors designed for better cropping action or poorer selectivity during feeding. This more profound understanding of the feeding habits of pachyrukhines further allows the suggestion of paleoecological factors that could have contributed to niche segregation between these long-term coexisting rodent-like taxa.

中文翻译：

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追踪 Paedotherium 和 Tremacyllus（Pachyrukhinae，Notoungulata）的古生物学，最新的 Sciuromorph 南美本土有蹄类动物 - 第一部分：鼻子和咀嚼装置

探究已灭绝形式的古生态学始终是一个挑战，特别是当所研究的分类群对应于古老且完全灭绝的进化枝的衍生生态形态时。在这篇文章中，对 36 个标本进行了详细的、主要是定性的比较分析，研究了新近纪 pachyrukhines Paedotherium 和 Tremacyllus 的咀嚼器官的构造和相关特征。牙齿形态和 pachyrukhines 重建的肌肉构造表明在咀嚼过程中是重要的中间成分，主要是碾碎而不是磨削，以及更强的咬合门牙的耦合和作用的前后运动。与专门的食叶习惯，特别是放牧习惯相比，这些行为更适合吃硬脆或膨胀的水果食物。眶下和腭孔形态和其他嘴部特征表明物体识别的触觉敏感性增加，并且与在啃硬食物期间保护牙龈的嘴唇折叠的存在一致。此外，在 Tremacylus 和 P. bonaerense 之间存在形态梯度，分别从相对较软和较小的食物的高选择，到专门的硬食物消耗以及对磨损和咀嚼努力的更高抵抗力（例如，最终与挖掘习惯有关），分别. Paedotherium typicum 具有中等特征，其门牙设计用于更好的种植动作或在进食过程中较差的选择性。