MORPHOLOGY AND PALEOECOLOGY OF THE LATE PLEISTOCENE EXTINCT DUNG BEETLE ONTHOPHAGUS PILAUCO (COLEOPTERA, SCARABAEIDAE, ONTHOPHAGINI)

The extinct dung beetle Onthophagus pilauco Tello, Verdú, Rossini & Zunino represents the southernmost paleorecord of the onthophagine dung beetle fauna in the New World. Here, we report new fore-, mid-, and posterior leg fossil remains of this extinct beetle and present a morphological comparison of the leg phenotypes observed in the fossil record. Moreover, we illustrate and describe the fossil legs and provide paleoecological inferences based on morphological analysis. We hypothesized that the differences in size and morphology of the remains are related to sexual dimorphism. To test this hypothesis, we applied parametric and non-parametric statistical approaches to the measurement of leg traits. Based on the leg traits identified in O. pilauco, we also discuss the phylogenetic affinities with modern species. Significant differences in foretibial morphology (i.e., length, width, tooth shape, curvedness) support the sexual dimorphism hypothesis. We found that O. pilauco’s forelegs shared a lack of secondary denticles with the O. hippopotamus species complex, although our diagnostic suggests that this trait evolved independently in these species groups. Finally, we discuss the paleoecology of the species based on the morphology of males and females and propose that this extinct species had paracoprid and hypophagic nesting behavior.