Abstract. The origin of biodiversity is a broad field that can be studied from a multitude of analytical perspectives. Macroevolutionary studies in secondarily aquatic tetrapods (SATs) tend to favour taxic diversity and not enough attention is paid to ecological disparity, which is essential to formulate integral conclusions. Here, we use non-metric multidimensional scaling (NMDS) and principal coordinate analyses (PCOa) to build an ecospace of marine tetrapods during the Cenozoic. We identify four main phases of ecospace evolution that illustrate how Cenozoic marine tetrapods recovered following the K/Pg mass-extinction event. Pulses of diversification reflect a bottom-up recovery following a positive feedback model and show how marine tetrapods adapted to changes in ocean systems and gave rise to the modern assemblage. The interpretation of these phases indicates that ecological diversity increased over time in a discrete incremental progression of disparity punctuated by stasis. Evaluation of macroevolutionary trends in the light of important events in geobiological history within the palaeontological record points to a composite of biotic and abiotic factors driving evolution, instead of one major catalyst being responsible for diversity.

Bio. Piero is a Peruvian PhD student at George Mason University working on the evolution of whales. He received a BA in Geography from the Pontificia Universidad Catolica del Peru and a Master’s degree in Paleobiology from the University of Bristol, UK. He has done fieldwork in the Peruvian Piscio Basin recovering and prospecting for marine mammal remains. This presentation is from his work at Bristol under Professor Mike Benton and is in the process of being published.