University of California, Davis
February 23, 2021
The evolution of ecological diversity: insights from strophomenide brachiopods
How do ecological traits evolve within clades and in what ways do trait differences explain how species coexist in ecosystems? Answering this question is central to explaining how biodiversity has accumulated over time and how we can conserve it in the future. In this talk, I will present results from my dissertation in which I examined changes in phylogenetic, morphological, and ecological diversity in the aftermath of the Late Ordovician mass extinction event. I will also discuss the perplexing questions that remain about brachiopods, how to begin addressing these questions, and the possible implications for paleoecological theory.
University College Dublin
February 16, 2021
Carbon release & sequestration: Extreme global climatic change events in Earth history – lessons for future climate mitigation
Earth system processes and feedback mechanisms regulate the release and sequestration of carbon, and therefore changes in the global carbon cycle throughout earth history. Past global change events are marked by major perturbations to the global carbon cycle. In this talk, I will explore processes that control carbon sequestration during the Toarcian Oceanic Anoxic Event (at ~183Ma), one of the largest global change events of the Phanerozoic. I will discuss how we can exploit this understanding to mitigate future climate change through plant-mediated silicate weathering based on controlled growth chamber experiments.
February 9 2021 21:00 UTC
Peculiar Palorchestes: Exploring forelimb form and function in a lost Australian giant
Reconstructing the palaeobiology of extinct taxa is challenging, especially when they have no living representatives and their anatomy differs greatly from animals alive today. The Palorchestidae were a rare and especially bizarre group of Australian marsupial megafauna known from the Oligocene through to their disappearance in the late Pleistocene. Reaching sizes over 1000 kilograms, these distant cousins of the wombat are best known for their ‘tapir-like’ skulls and supposed flexible trunk. With huge narrow claws and robust, oddly-proportioned forelimbs bearing near-flat humeroulnar articulations, how palorchestids used their limbs during life and the palaeoecological niche they occupied has been subject to much speculation.
In this talk I will share the latest findings from my PhD, using recently-described fossils and comparative biomechanics to explore the functional limits of the palorchestid forelimb in the context of other marsupials and potential analogues among living and extinct mammals. The apparent specialisation and functional trade-offs made by Palorchestes may underpin their ultimate demise, and highlight the extent of the marsupial ecomorphological diversity that was lost during the late Quaternary extinctions in Australia.
February 2, 2021
How in vivo data on extant species can shed light on the paleoecology of extinct species?
The reconstruction of the palaeobiology (ecology, behaviour and lifestyle) of an extinct species is a difficult exercise. Palaeobiological reconstructions assume that the morphology of a species reflects its ecological adaptation(s). Thus, to understand the adaptive nature of the morphology of the skeleton it is essential to study the relationships between bones and muscles in living species and their relation to ecology, locomotion, or behaviour while taking into account potential effects of shared ancestry. In this presentation, I show how in vivo data on extant species can shed light on the paleoecology of extinct species using two examples:1) the study of forelimb shape in relation to locomotor performance and grasping behaviour; 2) the study of the cranium and mandible shape in relation to bite force in order to make integrative inferences on feeding behavior in extinct species of strepsirrhine primates.
Florida State University
January 26, 2021
Data-Model Comparisons of Tropical Climate Change During the Common Era
The large-scale circulation of the tropical atmosphere is an essential component of the global climate system, regulating the transport of energy and moisture on regional to hemispheric scales. Billions of people around the globe depend on the seasonal and year-to-year variations in tropical rainfall that are driven by different components of this circulation, including the meridional Hadley circulation and the zonal Walker and monsoonal circulations. Importantly, it is highly uncertain how the tropical atmosphere and associated rainfall patterns will respond to continued anthropogenic warming trends, in part due to persistent biases in the representation of the tropical climate in state-of-the-art climate models. Paleoclimate records are an important tool with which to test the efficacy of such climate models, and in particular, the last 2,000 years (known as the Common Era) has been a major reconstruction target over the last decade due the relative abundance of data and the similarity of the Earth’s boundary conditions to our present climate. Paleoclimate reconstructions of the Common Era generally indicate a long-term cooling trend over the last millennium that was accompanied by widespread changes in tropical rainfall patterns. In this talk, I will review the evidence for these changes based on a compilation of ~70 paleo-hydroclimate records and compare the regional patterns in the reconstructions to those simulated by transient model simulations of the last millennium. While a number of robust regionally coherent patterns emerge from the proxy records, the model simulations exhibit weak forced long-term tropical rainfall changes that poorly agree with reconstructions, suggesting that either the tropical hydroclimate changes were unforced, or the models are unable to capture the forcings, feedbacks, or long-term hydroclimate responses over the last millennium. I will discuss the potential sources of the discrepancies and recommend future steps to better illuminate the mechanisms of the tropical hydroclimate changes over the last millennium.The origin of mammals and most of their evolutionary history took place during the Mesozoic, so their study is of paramount importance. After teeth, jaws are one of the most common fossils of Mesozoic mammals: can the functional performance of Mesozoic mammal jaws reveal their diets? In this talk, I present the results stemming from my PhD thesis on the relationship between jaw functional performance and diet in small mammals, using a combination of geometric morphometrics and biomechanical techniques, including mechanical advantage and finite element analysis.
January 19, 2021
The feeding ecology of Mesozoic mammals: a biomechanical approach
The origin of mammals and most of their evolutionary history took place during the Mesozoic, so their study is of paramount importance. After teeth, jaws are one of the most common fossils of Mesozoic mammals: can the functional performance of Mesozoic mammal jaws reveal their diets? In this talk, I present the results stemming from my PhD thesis on the relationship between jaw functional performance and diet in small mammals, using a combination of geometric morphometrics and biomechanical techniques, including mechanical advantage and finite element analysis.
December 8, 2020
The dirty truth: scientific colonialism in palaeontology
Analyses of past global biodiversity are severely hindered by sampling biases and gaps in the fossil record, previously been attributed to several geological and biological factors. However, global compilations of fossil occurrences not only reflect the physical aspects of the fossil record, but also document the historical compilation of this data over more than two centuries. This shows who has influence on the fossil data collection, access and availability by determining who has access to specimens and the ability to do research.
American Museum of Natural History
December 1, 2020
All the single forams: should we put a ring on area density?
Paleo-proxies of past atmospheric CO2 have demonstrated that continued unabated anthropogenic emissions could result in CO2 levels not documented since the Eocene period, 55 million years ago (Foster et al., 2017). However, many atmospheric CO2 paleo-proxies have large errors or are temporally and spatially limited. The area density proxy of foraminiferal shell thickness and calcification intensity has the potential to provide information about past ocean-atmosphere CO2 exchange and has the benefit of small sample requirements, simple analytical techniques, and the ability to re-use the analyzed foraminifera for other paleo-proxies. Some initial evaluation of this proxy has been done using ‘pristine’ foraminifera from sediment traps and plankton tows (Marshall et al., 2013; Osborne et al., 2016; Weinkauf et al., 2016) and through evaluation of cultured foraminifera (Davis et al., 2017; Henehan et al., 2017). Because foraminifera preserved in marine sediments can rarely be considered ‘pristine,’ we have to account for the additional influences associated with marine sediment burial and diagenesis before this proxy can be applied back in time. Using a series of multi-core core-tops collected from the southeastern Indian Ocean, we evaluate the reliability of utilizing sediment core Globigerina bulloides area density values to estimate surface ocean carbonate parameters. We find that confining area density measurements to a narrow range of values can account for influences related to cryptic speciation and shell preservation, up to a maximum area density value at which diagenesis begins to overprint the surface ocean signature. We investigate the relationship of surface ocean temperatures, carbonate ion concentrations, and phosphate concentrations with our newly defined G. bulloides area density ranges. Our developed calibrations indicate a relative insensitivity of G. bulloides area density to seawater properties, limiting their utility for reconstructing past surface ocean carbonate ion variability. Nevertheless, reconstructing the distribution of area density values in a given sample has the potential to provide valuable information on overall sample preservation as a shift in the distribution of the sample population from more well-preserved, lower area density shells to more poorly preserved, higher area density shells.