Figure 5.

(a) Posterodorsal view of the sphenoid region of Petrogale penicillata ZMB_EMB_MA585 showing the shape and location of the presphenoid. This bone is often overlooked in osteological studies; it originates from two different ossification centers at the anterior part of the braincase. Its ventral part connects successively to the orbitosphenoid, vomer, and basisphenoid, whereas the dorsal part forms two winglike lateral extensions that first connect to the frontal and at a later stage to the alisphenoid. Regarding the presphenoid, Clark and Smith²² reported that it connects to the orbitosphenoid almost immediately after the individual ossification of both bones. Although the orbitosphenoid is generally the first bone the presphenoid connects to in our data, it occurs late in development (median: 0.79), and the orbitosphenoid first connects to the maxilla (0.14), alisphenoid (0.69) pterygoid (0.69), and frontal (0.73) before connecting to the presphenoid. (b) Medial view of the middle ear region of Pe. penicillata ZMB_EMB_MA587 showing the close proximity of the goniale and ectotympanic.