User:Shaheenl/Lucy (Australopithecus)

Sacrum and Spine
While Examining Lucy's fossilized remains, it was believed that Lucy's sacrum had five fused elements. The sacrum was found to be in good condition with little damage done. Although the sacrum had five fused elements, the transverse processes of the most caudal element were not seen to connect to the segments craniad to it. This would result in researchers concluding that the sacrum suffered fossil damage which led to the fifth segment not connecting.

Although this was the case, recent studies are now coming out with new theories as to why Lucy's fifth sacral segment is in that shape. Some researchers conclude that Lucy has only four sacral segments. Published in the American Journal of Physical Anthropology, researchers suggest that fossil damage did not shorten the transverse process and that Lucy's sacrum was in this state from the beginning. This specific study points to Lucy's sacrum having four sacral segments which researchers say conforms with the "long-back" model of hominoid vertebral evolution. There are some disagreements in the community about the fifth sacral segment and if fossil damage was enough to change the fifth segment or if it was originally in that state. Discussed in the Journal, researchers conclude that Lucy having only four sacral segments is consistent with other findings related to early Miocene hominoids.

Lucy's back is associated with approximately 9 vertebrae. Although Lucy was found with a relatively intact and well preserved sacrum, she was missing pieces in her spinal column. Lucy's discoverers and later workers had given the vertebrae provisional level assignments (Positions in the vertebral column) to locations within the vertebral column. Interestingly, some vertebrae were in worse conditions than others. Lucy had a worn out upper thoracic neutral arch. Researchers have yet to find a cause as to why this particular vertebrae was in worse condition than the other pieces. While accessing and restructuring Lucy's spinal column, it was noted to have been missing pieces that leave it incomplete. Not including an oddly worn out upper thoracic neutral arch, and the lumbar vertebrae, the other remaining thoracic vertebrae were compiled to form an incomplete formation. The formation was arranged from the sixth thoracic vertebrae (T6) to its caudal end (T12), with the seventh thoracic vertebrae (T7) missing. Currently the the continuity differs in the thoracic series between researchers and it being reevaluated. Although there are new studies and reassessments being done, it does not refute previous work or conclusions about Lucy's spine.