Boyer diss 2009 1046..

Figure 4.47. Caudal vertebrae comparisons. A, proportional length of the first 18 caudal
vertebrae of Plesiadapis cookei, Cynocephalus, and a subset of the comparative sample
(standardized to sacrum length of each specimen by taking the natural log ratio of each
vertebral length to the sacrum length). Note that the last several vertebrae of the tail of
Cynocephalus decrease in proportional length more drastically than in the other taxa.
Also note that, after the euprimate Saguinus, P. cookei has the proportionally longest
inferior caudal vertebrae starting at Ca6. B, cumulative proportional length shows that by
the 18 th caudal vertebra, P. cookei has the second longest tail relative to its sacrum (for
the calculation of P. cookei’s tail length, missing vertebrae Ca2-3 were assumed to each
be the same length as Ca1, and missing Ca5 was represented by the average between Ca4
and Ca6). Although Cynocephalus has the third longest tail at Ca18, this represents the
tip of its tail, while all other taxa in this sample have additional vertebrae, including P.
cookei.
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