Fig. 7
From: From Land to Water: the Origin of Whales, Dolphins, and Porpoises
Detail of the ear region of a skull in Fig. 6 (RR 208). M3 is the last molar in the upper jaw, and the mandibular fossa is the jaw joint. The middle ear is filled with air in life and has a bony wall, similar in shape to a nutshell. The bony wall is broken in this specimen, showing the thickness of the wall (medial tympanic wall). It also exposes the inside of the middle ear, which is filled with sediment here