Extended Data Fig. 1: Cranio-mandibular morphology of J. kielanae (holotype IVPP V20778).
From: Cretaceous fossil reveals a new pattern in mammalian middle ear evolution
a, Skull in dorsal view and right mandible in lateral view. b, Skull in ventral view, left mandible in lateral view, and right mandible in medial view. c, Close-up view of cranio-mandibular features. d, Close-up medial view of the right dentary. The flat glenoid fossa accommodates the mandibular condyle, which is positioned below the occlusal level of the lower molars and faces posteriorly in IVPP V20778. Together with the distinct masseteric fossa—which presumably provides attachment for a well developed masseteric muscle, inserting anteriorly below P4—the glenoid fossa produces a palinal (posterior) power stroke with distinct posterior chewing.
