Molar crown morphometrics in Paucituberculata (Mammalia: Marsupialia)

Abstract

The Paucituberculata are a group of marsupials endemic to South America, recorded from the Early Eocene to the present. In terms of taxonomy and qualitative morphology, paucituberculatans are a quite diverse and disparate group, especially considering their extinct representatives. This study aimed to investigate the variability in the quantitative morphology of paucituberculatans in the context of the largest morphometric study of the group performed to date. Due to the fragmentary fossil record, this work focused on lower dental morphology which allowed us to compare around 95% of paucituberculatan species through the measurement and analysis of almost 1500 specimens. Dental measurements of 27 variables were analysed by Principal Component Analysis and Partial Least Squares correlation as exploratory methods. As a result, it is shown that the continuous variability is expressed not only in size differences among species but also in morphological variability of individual teeth, and differences in size and proportions along the molar row. We conclude that paucituberculatans are a group of important morphological diversity regarding quantitative morphology. Many of the quantitative taxonomic features discussed in the literature were corroborated in this study. In addition, we discussed potential evolutionary and palaeoecological implications of this study, highlighting prospects for future studies.