Boyer diss 2009 1046..

the skull (Fig. 2.1). The length of the eam from its anterolateralmost point to the crista
tympanica is roughly 5.5 mm. The anteroposterior diameter is larger, 5.75 mm. Thus,
although the ectotympanic is not ring-like, it is certainly not tubular. It is merely
moderately laterally expanded. While the remains of the crista tympanica can be
recognized as a raised, ring-like ridge on the internal surface of the ectotympanic, the
ectotympanic does not preserve evidence of a distinct “annular component.” Whether the
ectotympanic formed a substantial component of the bullar walls and floor is not
discernable from this specimen.
Occipital.—The basioccipital is preserved on the ventral surface of the skull
between the two petrosals (Figs. 2.2, 3). It measures 8.46 mm in anteroposterior length.
The anterior end, where it would have met the basisphenoid at the spheno-occipital
synchondrosis, measures 3.25 mm in mediolateral width (Fig. 2.2: 27). The
anteroposterior midpoint is only 2.96 mm wide and the posterior end is 4.36 mm wide
(Fig. 2.2). HRxCT reveals it to be a thin bone, but that may only mean that any dorsal
thickness to the bone has been pulverized. The only clearly preserved remnants of the
exoccipitals are the left occipital condyle (Figs. 2.2, 3: 28) and the corresponding
hypoglossal foramen (Figs. 2.2, 3: 29). The root of the right occipital condyle is
preserved, which is only informative inasmuch as it delineates the boundary of the
foramen magnum (Figs. 2.2, 3: 30). The occipital condyle measures 3.87 mm
dorsoventrally by 2.47 mm mediolaterally. The hypoglossal foramen is located a short
distance anterior to the condyle. It is 1.03 mm by 0.86 mm. The hypoglossal canal is
split in two by a septum that is inset within it. The foramen magnum appears only
slightly distorted; its mediolateral width measures about 7.4 mm. The exoccipital and
47