Abstract: A unique canal (calcaneal canal) running diagonally through the calcaneus was commonly considered as characteristic for lagomorphs, both extant and fossil, but absent in rodents and otherpertinent lagomorph relatives. However, our investigation of a calcaneus from the Middle Paleocene of Qianshan, Anhui Province and specimens previously grouped in Mimotonidae also shows presence of canals on calcaneus bones. To further explore the unique character, we scanned calcanei of Ordolagus, Mimolagus, Gomphos,Rhombomylus, and Oryctolagus using microCT and investigated the calcanei in some other related taxa under microscope. Three-dimensional reconstructions of the calcanei based on CT data of these taxa confirmed the presence of apertures traversing the large medullary cavity. The diagonally oriented calcaneal canal is present not only in lagomorphs, but also in non-lagomorph duplicidentates, such as Mimotona, Gomophos, and simplicidentates, such asRhombomylus, though smaller in size. Hence, the presence of calcaneal canal may be one of the synapomophic characters for Glires, not only for the order Lagomorpha. The shared calcaneus character confirms the close relationship between Simplicidentata and Duplicidentata. 

摘要： 2002年Bleefeld和Bock发现跟骨上一个独特的解剖结构——跟骨管——仅在现生与化石兔形目种类中存在，而在啮齿类以及相关类群中缺如，并认为这个独特的解剖特征支持了兔形目是一个单系类群。对安徽潜山古新世地层中发现的基干啮型类标本(IVPP V 7422)的观察表明其跟骨上也存在清晰的跟骨管，使得我们重新审视这一独特解剖特征。结合显微镜观察与CT扫描技术，发现兔形目种类，如Dawsonolagus, Ordolagus等存在较大的跟骨管，其进口与出口皆与骨体内部髓腔贯通；在双门齿啮型类如Mimolagus, Gomphos, 单门齿啮型类Rhombomylus上也存在清晰的跟骨管。因此，跟骨管的存在可能是啮型类的共近裔性状，也支持了兔形类与啮齿类具有更近的亲缘关系。