Boyer diss 2009 1046..

including the lumbar, sacral and proximal part of the caudal region. Generally speaking,
vertebrae described in this section were identified as being part of the thoracic region by
the presence of rib facets on the body or transverse processes and in some cases by the
orientation of the zygapophyseal facets. The craniocaudal position of a given thoracic
vertebra, other than whether it comes before or after the diaphragmatic position is
difficult to determine due to extensive postmortem deformation that prevents assessments
through articulation or detailed measurements. Often centrum length, height or overall
size increases progressively from anterior to posterior. The first thoracic vertebra (Fig.
4.42A) is craniocaudally shorter than the others, but there is no pattern of increase in the
remaining prediaphragmatic vertebrae (Table 4.27; Fig. 4.42B-I). This is demonstrated
beyond any doubt by the only two vertebrae preserved in articulation (Fig. 4.42E), in
which the more cranial one is slightly, but definitely, longer. However, the two
postdiaphragmatic thoracic vertebrae (Fig. 4.42J-K) are longer than the ten vertebrae
cranial to them. The first three thoracic vertebrae exhibit dorsoventrally shallow cranial
and caudal centrum facets, while T4-T10 are deeper, with no discernable pattern of
increase or decrease. T12 cannot be measured cranially and T13 cannot be measured
caudally, but together they are the deepest caudally and deepest cranially (respectively) in
the thoracic region. Centrum mediolateral widths are even less tractable. T1 is wider
cranially than all vertebrae that follow until T13. Caudally it is the widest of the thoracic
region. Of the vertebrae with preserved transverse processes, the most caudal ones are
mediolaterally narrower than the more anterior ones (i.e., Fig. 4.42E vs. 4.42H-I). Of
those with intact laminae and spinous processes, the more posterior postions have more
vertically oriented processes. The prediaphragmatic spinous processes are all longer
366