Five partially preserved mammaliaform petrosals recovered from Middle Jurassic sediments of the Berezovsk coal mine (Krasnoyarsk Krai, Russia) show similarities to other early mammaliaforms like the morganucodontan Morganucodon and the docodontan Haldanodon in having an inflated promontorium and a curved and apically inflated cochlear canal, but they are distinct from dryolestoid and derived mammalian petrosals by the weak coiling of the cochlear duct and the presence of a perilymphatic foramen with an open perilymphatic sulcus. The two larger and robust specimens exhibit striking similarities to docodontan petrosals. Inside the bone an intricate circumpromontorial venous plexus was discovered, as recently described for the docodontan Borealestes, confirming that this structure is consistently present in basal non-mammalian mammaliaforms. The three smaller and slender petrosals probably belong to haramiyidans and are unique in showing a septum-like structure medially along the cochlear nerve entrance. The protruding perforated bony bar, which is preserved in two of the three, is interpreted here to be a remnant of a bony septum with multiple foramina for cochlear nerve fibres, representing an autapomorphic feature of Haramiyida. This newly described passageway for nerve fibres shows that the formation of the osteological structure surrounding the nervous pathways of the cochlea is more plastic among the non-mammalian mammaliaforms than previously thought.

中文翻译：

---

来自西西伯利亚（俄罗斯）的侏罗纪哺乳动物形岩层及其对早期哺乳动物内耳解剖学的影响

从别列佐夫斯克煤矿（克拉斯诺亚尔斯克边疆区，俄罗斯）的中侏罗纪沉积物中发现的五个部分保存完好的哺乳动物形岩体与其他早期哺乳动物形体（如 morganucodontan Morganucodon 和 docodontan Haldanodon）相似，具有膨胀的海角和弯曲且顶部膨胀的耳蜗管，但由于耳蜗管的卷曲较弱，并且存在带有开放的外淋巴沟的外淋巴孔，它们与干卵和衍生的哺乳动物岩骨不同。这两个更大、更结实的标本与多齿龙岩有着惊人的相似之处。在骨骼内部发现了一个错综复杂的环前静脉丛，正如最近对北极齿鲨所描述的那样，证实了这种结构始终存在于基础的非哺乳动物哺乳动物中。三个较小而细长的岩骨可能属于haramiyidans，并且在沿耳蜗神经入口内侧显示出隔膜状结构是独特的。突出的穿孔骨条保留在三个中的两个中，在这里被解释为具有多个耳蜗神经纤维孔的骨隔的残余物，代表了Haramiyida的自生特征。这种新描述的神经纤维通道表明，在非哺乳动物哺乳动物中，围绕耳蜗神经通路的骨结构形成比以前认为的更具可塑性。保留在三个中的两个中，在这里被解释为具有多个用于耳蜗神经纤维的孔的骨性隔膜的残余物，代表了Haramiyida的自变形特征。这种新描述的神经纤维通道表明，在非哺乳动物哺乳动物中，围绕耳蜗神经通路的骨结构形成比以前认为的更具可塑性。保留在三个中的两个中，在这里被解释为具有多个用于耳蜗神经纤维的孔的骨性隔膜的残余物，代表了Haramiyida的自变形特征。这种新描述的神经纤维通道表明，在非哺乳动物哺乳动物中，围绕耳蜗神经通路的骨结构形成比以前认为的更具可塑性。