Gaffneylania auricularis

GAFFNEYLANIA AURICULARIS

Only the posterior region of the braincase of G. auricularis is preserved; the cranial endocast is missing the forebrain and most of the midbrain ( Fig. 3 View Figure 3 ). The hindbrain, however, is complete and exhibits several traits, allowing comparisons with the other two meiolaniids ( Fig. 5B, E, H View Figure 5 ).

Cranial endocast proper

The medulla oblongata is a more or less horizontal tube, with a flat ventral surface and a convex dorsal margin unlike the straight and posterodorsally-oriented dorsal margin present in M. platyceps and N. argentina ( Fig. 5E View Figure 5 ). The posterior-most section of the pituitary of G. auricularis is reconstructed, indicating it was a small structure, as in other turtles.

The posterior margins of CN V are preserved in the braincase. CN VI is reconstructed on the left side of the endocast. This passage is small in diameter, short and anteroventrally projected ( Fig. 5E, H View Figure 5 ). CN VII is a small foramen posterior to CN V ( Fig. 4 View Figure 4 ), which enters the hiatus and is observed in lateral view because the lateral wall of the hiatus is broken. CNs IX–XI leave the endocranial cavity through a single opening, the foramen jugulare anterius (= metotic foramen), as in M. platyceps and other studied turtles. This passage runs posterolaterally and leads into the recesus scalae tympani. A markedly smaller passage diverges from the main passage dorsally before entering the recesus scalae tympani, and corresponds to CN IX ( Fig. 4 View Figure 4 ).