CHARACTER SELECTION AND THE QUANTIFICATION OF MORPHOLOGY
The effect of varying the number of characters used in the quantification of morphology was examined with a morphologic dataset of early Paleozoic crinoids. A set of characters was recently compiled as part of the Assembling the Echinoderm Tree of Life project and includes 178 multistate and binary characters that encompass the entire skeletal morphology of the organisms (holdfast, stem, calyx, tegmen, and arms). Two hundred early Paleozoic crinoids were coded and the resulting matrix was analyzed to produce a morphospace using principal coordinate analysis. A rarefaction analysis was conducted on the dataset in which a subset of characters was randomly chosen, analyzed, and the structure of the resulting morphospace was then compared to the morphospace built using the original character matrix in terms of the position of taxa along the primary axis, the amount of variance, and the relative distance between taxa. The results indicate that with this character suite, similar results can be obtained using only 10-15% of the character matrix, i.e. 20-30 characters out of 178. Therefore, large character sets may not be required to detect the major morphologic patterns that are of interest in paleontological studies.