Tumelty Molly, Lautenschlager Stephan
School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, UK.
The Lapworth Museum of Geology, Birmingham, UK.
Anat Rec (Hoboken). 2025 Sep;308(9):2371-2391. doi: 10.1002/ar.25630. Epub 2025 Jan 24.
Determining the ecology of fossil species presents considerable challenges due to the often fragmentary preservation of specimens. The mammaliaform Hadrocodium wui from the Jurassic of China is known only from the cranium and mandible but may have had a fossorial lifestyle. It shares morphological similarities with talpid moles and soricid shrews and is closely related to other fossorial mammaliaforms. However, the lack of postcranial elements has so far precluded a definitive assessment regarding its fossorial behavior. Using a combination of geometric morphometric analysis of the lower mandible and finite element analyses of the cranium, comparisons between H. wui and extant groups are made. H. wui resembles talpid moles more closely than shrews in mandible shape. However, there are more similarities between H. wui and semi-fossorial/semi-aquatic moles than fully fossorial moles. The skull of H. wui is particularly weak in every tested biomechanical scenario when compared to the related mammaliaform Morganucodon oehleri and talpid moles. This weakness is potentially a result of the reduction in thickness of the zygomatic arch. In contrast, the shrew crania show similar stress magnitudes and distribution. These results imply that H. wui was not fully fossorial and fed on a diet of softer invertebrates. Skull morphology may therefore not be sufficient to infer fossoriality in forelimb-digging species.
由于化石标本的保存往往不完整，确定化石物种的生态环境面临着巨大挑战。来自中国侏罗纪的哺乳形动物吴氏巨颅兽仅知其颅骨和下颌骨，但可能具有穴居的生活方式。它与鼹形鼠和鼩鼱在形态上有相似之处，并且与其他穴居哺乳形动物关系密切。然而，迄今为止，由于缺少颅后骨骼元素，无法对其穴居行为进行明确评估。通过结合下颌骨的几何形态测量分析和颅骨的有限元分析，对吴氏巨颅兽与现存类群进行了比较。吴氏巨颅兽在下颌形状上与鼹形鼠的相似性高于与鼩鼱的相似性。然而，吴氏巨颅兽与半穴居/半水生鼹鼠之间的相似性比与完全穴居的鼹鼠更多。与相关的哺乳形动物奥氏摩根齿兽和鼹形鼠相比，在每种测试的生物力学情况下，吴氏巨颅兽的头骨都特别脆弱。这种脆弱可能是颧弓厚度减小的结果。相比之下，鼩鼱的颅骨显示出相似的应力大小和分布。这些结果表明，吴氏巨颅兽并非完全穴居，以较软的无脊椎动物为食。因此，头骨形态可能不足以推断前肢挖掘物种的穴居性。
