Data from: Palaeoecological inferences for the fossil Australian snakes Yurlunggur and Wonambi (Serpentes, Madtsoiidae)

Madtsoiids are among the most basal snakes, with a fossil record dating back to the Upper Cretaceous (Cenomanian). Most representatives went extinct by the end of the Eocene, but some survived in Australia until the late Cenozoic. Yurlunggur and Wonambi are two of these late forms, and also the best-known madtsoiids to date. A better understanding of the anatomy and palaeoecology of these taxa may shed light on the evolution and extinction of this poorly known group of snakes and on early snake evolution in general. A digital endocast of the inner ear of Yurlunggur was compared to those of 81 species of snakes and lizards with known ecological preferences using three-dimensional geometric morphometrics. The inner ear of Yurlunggur most closely resembles both that of certain semiaquatic snakes and that of some semifossorial snakes. Other cranial and postcranial features of this snake support the semifossorial interpretation. While the digital endocast of the inner ear of Wonambi is too incomplete to be included in a geometric morphometrics study, its preserved morphology is very different from Yurlunggur and suggests a more generalist ecology. Osteology, palaeoclimatic data, and the palaeobiogeographic distribution of these two snakes are all consistent with these inferred ecological differences.

玛德松蛇科（Madtsoiidae）是最为原始的蛇类类群之一，其化石记录可追溯至晚白垩世（森诺曼阶）。该科绝大多数类群在始新世末期走向灭绝，但仍有部分支系在澳大利亚延续至晚新生代。尤伦贡蛇（Yurlunggur）与沃纳比蛇（Wonambi）便是其中两类晚存续的代表，也是目前已知知名度最高的玛德松蛇科物种。
对这两个类群的解剖结构与古生态特征开展更深入的研究，或可为阐明这一鲜为人知的蛇类类群的演化与灭绝历程，乃至整体早期蛇类的演化脉络提供重要启示。研究人员借助三维几何形态测量学（three-dimensional geometric morphometrics），将尤伦贡蛇的内耳数字化颅内模与81种已知生态偏好的蛇类和蜥蜴的内耳颅内模进行了对比分析。结果显示，尤伦贡蛇的内耳结构与部分半水生蛇类以及部分半穴居蛇类的内耳结构最为相似。该蛇的颅骨骼与颅后骨骼特征也进一步佐证了其半穴居的生态推断。
尽管沃纳比蛇的内耳数字化颅内模保存状况残缺严重，无法纳入本次三维几何形态测量学研究，但其保留的形态结构与尤伦贡蛇差异显著，暗示其生态位更为泛化。两类蛇的骨骼学数据、古气候资料以及古生物地理分布，均与上述推断出的生态差异相吻合。