The Australopithecus afarensis partial skeleton A.L. 288-1, popularly known as "Lucy"
is associated with nine vertebrae. The vertebrae were given provisional level assignments
to locations within the vertebral column by their discoverers and later workers. The
continuity of the thoracic series differs in these assessments, which has implications
for functional interpretations and comparative studies with other fossil hominins.
Johanson and colleagues described one vertebral element (A.L. 288-1am) as uniquely
worn amongst the A.L. 288-1 fossil assemblage, a condition unobservable on casts of
the fossils. Here, we reassess the species attribution and serial position of this
vertebral fragment and other vertebrae in the A.L. 288-1 series. When compared to
the other vertebrae, A.L. 288-1am falls well below the expected size within a given
spinal column. Furthermore, we demonstrate this vertebra exhibits non-metric characters
absent in hominoids but common in large-bodied papionins. Quantitative analyses situate
this vertebra within the genus Theropithecus, which today is solely represented by
the gelada baboon but was the most abundant cercopithecoid in the KH-1s deposit at
Hadar where Lucy was discovered. Our additional analyses confirm that the remainder
of the A.L. 288-1 vertebral material belongs to A. afarensis, and we provide new level
assignments for some of the other vertebrae, resulting in a continuous articular series
of thoracic vertebrae, from T6 to T11. This work does not refute previous work on
Lucy or its importance for human evolution, but rather highlights the importance of
studying original fossils, as well as the efficacy of the scientific method.