The Stagodontidae include the largest metatherians known from the Cretaceous of North America. Of the recognized species of the stagodontid genus Eodelphis, E. cutleri is larger and has a more robust dentary, more inflated premolars, and third premolars specialized for crushing, as opposed to the more gracile E. browni. These differences have led to the hypothesis that an E. cutleri-like ancestor gave rise to Didelphodon—another, mostly younger, stagodontid, which has been interpreted as a durophagous predator-scavenger. If correct, E. cutleri would be expected to show more morphological adaptation toward durophagy than E. browni does. Here, we describe two new dentary fossils referable to E. browni and test the evolutionary hypothesis by applying beam theory to estimate bending force capabilities of 22 dentaries of Cretaceous stagodontids and other metatherians. The resulting diversity of bending force profiles of the sampled dentaries implies that Cretaceous metatherians had a wide range of feeding behaviors. Among the stagodontids, E. cutleri has a mediolateral bending force profile of the dentary that is more similar to that of Didelphodon than it is to that of E. browni; whereas its dorsoventral bending force profile is more similar to that of E. browni. These results indicate that anteriorly the dentary of E. cutleri was capable of resisting high torsional stresses from hard-object feeding but lacked other dorsoventral buttressing associated with exceptionally high bite forces of Didelphodon. Our results imply that some morphological changes associated with durophagy evolved twice within this clade, independently in E. cutleri and Didelphodon.

中文翻译：

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晚白垩世Metatherian Eodelphis 的新标本与Stagodontidae 硬物摄食的演变

Stagodontidae 包括已知的北美白垩纪最大的后兽类。在公认的 stagodontid 属 Eodelphis 中，E. cutleri 更大，具有更坚固的牙齿、更膨胀的前磨牙和专门用于压碎的第三前磨牙，而不是更纤细的 E. browni。这些差异导致了一种假设，即一种类似 E. cutleri 的祖先产生了 Didelphodon——另一种主要是年轻的 stagodontid，它被解释为一种无食性的捕食者-清道夫。如果正确，E. cutleri 预计会比 E. browni 表现出更多的对硬食性的形态适应。在这里，我们描述了两个与 E 相关的新齿类化石。Browni 并通过应用梁理论来估计白垩纪 stagodontids 和其他 metatherians 的 22 齿的弯曲力能力来测试进化假设。由此产生的采样齿的弯曲力曲线的多样性意味着白垩纪后兽类具有广泛的摄食行为。在 stagodontids 中，E. cutleri 的齿的中外侧弯曲力分布更类似于 Didelphodon，而不是 E. browni；而其背腹弯曲力分布更类似于 E. browni。这些结果表明，E. cutleri 的前齿能够抵抗来自硬物进食的高扭转应力，但缺乏与 Didelphodon 异常高咬合力相关的其他背腹支撑。