Prediction of marsupial body mass

Cranio-dental variables are correlated with body mass in marsupials, using a species data-set derived from extant australidelphian representatives, to predict body mass in fossil species. Thirty-eight extant australidelphian species, including 10 dasyuromorphians, 22 diprotodontians, 1 notoryctomorp hian and 5 peramelemorphians, were analysed. Where sexual dimorphism was pr ominent, genders were evaluated separately. Twenty-nine cranio-dental varia bles were measured for each specimen and species averages calculated. Body masses were taken as recorded for each specimen or as published species ave rages. The cranio-dental measures for each morpho-species were then regress ed against average body mass in four distinct data-sets: (1) the entire spe cies sample, (2) only dasyuromorphian taxa, (3) only diprotodontians, and ( 4) all species excluding dasyuromorphians. Each cranio-dental variable was then ranked according to various error statistics and correlation coefficie nts. Results suggest that predictors of body size in eutherians (such as fi rst lower molar area), commonly used to estimate body mass in marsupials ma y not be reliable or accurate indicators. Significant differences in the us efulness of predictor variables between taxonomic data-sets were also obser ved. Total jaw length is the most reliable predictor for diprotodontians, a s well as for all species combined, whereas lower molar row length appears to be more appropriate for dasyuromorphians. Multiple variable regressions variably offer more precision than those derived from individual parameters .