Figure 6. Proposed middle ear structure across some extant vertebrate taxa.

Skulls are shown in black, tympanic ears in yellow, connections between the ears (Eustachian tubes or through the buccal cavity) in green. The dashed line on the avian diagram indicates trabeculated bone. The proposed diapsid ancestral condition is also shown. The dashed branch to testudines indicates their suggested phylogenetic position [33]–[35].