Investigating niche partitioning and feeding behavior in fossil caimanines of the Amazon through multi-body analysis, finite element analysis and morphospace analysis

Abstract

The fossil fauna of caimanine crocodylians (Crocodyliforms, Caimaninae) during the Miocene of the Amazon in South America is one of the most taxonomically diverse and morphologically disparate of the evolutionary history of crocodyliforms. It includes taxa considered as apex predators (Purussaurus), gulp-feeders (Mourasuchus), durophagous (Caiman brevirostris) and generalists (Acresuchus), which suggests the presence of niche partitioning among these forms. However, nearly all assessments on the feeding habits and niche partitioning of these taxa have been largely theoretical and speculative, while empirical, quantifiable assessments are notably lacking. This project has the objective of providing a thorough assessment on the feeding habits, paleoecology and niche partitioning of the fossil caimanines of the Miocene of Amazon. The feeding habits of key taxa of the fauna (Acresuchus, C. brevirostris, Mourasuchus and Purussaurus) will be investigated through the combination of two techniques, the Multi-Body Analysis (MDA, which has only recently been employed in biology and paleontology), and the Finite Element Analysis (FEA), both based on the use of CT-scans of specimens of the taxa of interest. Both techniques will be employed separately (the FEA-only approach is part of the ongoing project of the applicant) and in conjunction; as such, three distinct approaches will be employed. The proposed combination of techniques allows estimations of bite force, maximum opening angle of the mandibles, and feeding simulations that will allow the estimation of stress and strain distribution along the skull bones and teeth of the analyzed taxa. The results of these estimations will determine the nature and size of prey consumed by each taxon, as well as their food processing mechanisms and foraging techniques. The results of the MDA-only and of the combined MDA and FEA approaches will complement the FEA-only analyses of the ongoing project of the applicant; the results of the three approaches will be compared regarding their efficiency and potentialities. Additionally, a morphospace analysis will be performed to examine the niche partitioning hypothesis between the fossil caimanines of the Amazon area. This analysis will also be performed through the CT-scans of the specimens, using geometric morphometrics characters to establish the morphospace occupation of each taxon, therefore elucidating whether or to which degree the ecological niches of the analyzed taxa were separated or overlapped. Therefore, these analyses will provide the first thorough assessment on the feeding habits and niche partitioning of one of the most diverse and interesting crocodyliform fossil faunas: the South American Miocene caimanines of the Amazon. (AU)