Successional stages of a Maastrichtian plesiosaur fall community from Antarctica

Abstract

Research on ecological successions in recent skeletal remains, such as those of whales, has revealed specific colonization patterns and four distinct succession phases. These succession patterns can also be inferred in the fossil record from evidence such as bioerosion traces, bone encrustation, and associated body fossils. The study of ecological successions in fossil bones of Mesozoic marine reptiles not only helps to understand the phases of degradation and entombing in the past but also contributes to our knowledge of the communities associated with these carcasses during that time. In this work, the presence of sclerobionts (represented by micro and macroborings) in bone remains of a plesiosaur from the upper Maastrichtian of Antarctica was identified and described, interpreting the phases of ecological succession in a high-latitude marine environment. Macroborings were assigned to Trypanites and Osedacoides. The microborings, similar to Wedl tunnels, were attributed to cyanobacteria and fungi, indicating that the bones were exposed for a long time. Furthermore, framboid pyrite in the bones shows anaerobic stages associated with bacterial activity. The four known stages of ecological succession were documented: the mobile scavenger stage, identified by bite marks; the opportunistic enrichment stage by Osedacoides; the sulfophilic stage, marked by modified vascular channels filled with pyrite; and the reef stage, by Trypanites traces, which indicate colonization by organisms before final burial. These findings enhance our understanding of the interactions between microorganisms and mineralization in ancient marine vertebrates, and aid in reconstructing paleocommunities associated with marine reptile falls, offering valuable insights into past ecosystem dynamics.