Students and Postdocs

Postdoctoral Associates

James Lamsdell

My research interests centre around exploring patterns in macroevolution and macroecology through a phylogenetic framework. My work specifically focuses on Palaeozoic arthropods, with a particular focus on aquatic chelicerates (eurypterids and xiphosurans). I have a specific interest in applying phylogenetic methodologies to fossil groups, both to resolve issues of arthropod systematics and to tackle broader macroevolutionary questions, especially surrounding mass extinction events. My work combines phylogenetic and morphometric analyses to quantify patterns of morphological change in response to extinction events and subsequent recoveries, and compares changes in evolutionary rates and ecological preferences to search for selective patterns across these events and subsequent recoveries. With these data I am able to explore how different evolutionary lineages respond to different extinction forcing mechanisms.

I am currently studying specimens from a series of Ordovician Lagerstätten, particularly from the Winneshiek Shale of Iowa and Fezouata in Morocco, some of which represent the oldest known eurypterids. The Ordovician is a particularly important period of geologic time, witnessing the transition from a predominantly Cambrian-type fauna to the more typical Palaeozoic fauna. Aside from my work on eurypterids and macroevolutionary research, other research interests include: the importance of lagerstätten for informing on arthropod evolution; studying evidence for arthropod development in the fossil record and the role of heterochrony in arthropod evolution, including the importance of ontogenetic data for phylogenetic analyses and calculations of morphospace; the relationship between diversity, morphological disparity, and ecological variety; and the generality of ecological preferences across and within clades.

Sean McMahon

I am a geobiologist and geomicrobiologist with broad interests in early life and astrobiology.

At Yale, I am developing new experimental techniques for examining the interplay of decay and mineralization in the formation of exceptionally preserved fossils. Microorganisms, chiefly fungi, bacteria and archaea, are critically involved in both of these processes and interact multifariously with the physical, chemical and mineralogical environment of the decaying carcass. Unpicking these complex interactions requires novel applications of microbiological and histological techniques. The results could greatly improve our understanding of biases in the Precambrian fossil record, in particular that of the well-known Ediacara biota, which consists of the oldest known complex multicellular organisms on Earth.

Other research interests include the origin of life, Precambrian microfossils and other biosignatures, the geobiology of the deep subterranean biosphere, and the possibility of life on Mars.

Erin Saupe

The goal of my research is to explore how life evolved on our dynamic planet, with emphasis on understanding how biogeographical processes impact macroevolution. Specifically, I am interested in elucidating the controls on species’ responses to environmental change, and I do so by integrating biological data with information obtained from the fossil record. Although spiders are my true passion, I use mollusks for most of my macroecological and macroevolutionary research because of their exceptional fossil records.

My current work investigates the controls on biotic turnover events, with focus on the post-Pliocene regional mass extinction that occurred in the southeastern USA. I am working to explicitly and quantitatively test if temperature changes generated observed patterns of biotic turnover using both empirical and simulation data. Analyses will determine the factors that led to the biotic turnover, which is vital for understanding current and future diversity changes, and will also identify whether species’ niche characteristics (e.g., niche breadth) impact evolutionary outcomes.

In addition to my macroevolutionary research, I am working to clarify macroecological concepts and theories, particularly as they relate to the application of Ecological Niche Modelling (ENM). Current research focuses on understanding the relationship between genetic distance between geminate species pairs and niche differentiation. 

Lidya Tarhan

My research interests center upon developing a multidisciplinary understanding of ancient life during key intervals in earth history. I am especially intrigued by the interplay between animals and environments (particularly animal-substrate-microbe interactions) and the role of metazoans as ecosystem engineers in both modern and ancient settings. I am also interested in the processes of fossilization and the role preservational processes play in modifying the stratigraphic records of both ecosystems and environments. My research is heavily field- as well as laboratory-based.

I am currently investigating the biogeochemical, taphonomic and diagenetic pathways responsible for the exceptional silicified preservation of Ediacaran and lower Paleozoic soft-bodied faunas (‘Ediacara-style’ preservation), using a combination of field-based, paleontological, petrographic, experimental and geochemical techniques.

Other research interests include the advent and development of infaunal mixing by burrowing animals in the early Paleozoic; modern marine microbialite-infauna interactions; Ediacaran taphonomy and paleoecology; turnover between Ediacaran and Cambrian faunas; and the role of environment, taphonomy and tracemaker diversity in the formation, preservation and distribution of trilobite-produced trace fossils such as Rusophycus and Cruziana.

Peter Van Roy

The “Cambrian Explosion” and the “Great Ordovician Biodiversification Event” are the two major adaptive radiations of the Phanerozoic. The Cambrian Explosion saw the apparently sudden appearance of all major metazoan phyla and the establishment of complex ecosystems. The subsequent Great Ordovician Biodiversification witnessed an exponential increase in diversity within animal phyla. The origins of this critical event, establishing the “Palaeozoic Evolutionary Fauna” which dominated the biosphere for the next 240 Ma, are complex and hotly debated. Exceptionally preserved biotas have an important role to play in our understanding of the Ordovican radiation, but their scarcity, and the fact that the few previously reported examples are taxonomically depauperate and from restricted marine environments, has resulted in this event being studied almost exclusively using “shelly” faunas. The main focus of my work is on an exceptionally preserved biota from the Lower Ordovician of south-eastern Morocco. This represents the first Early Ordovician Konservat-Lagerstätte from a normal, open marine setting, and hence fills an important gap in our knowledge. Apart from systematic work on this biota, I also intend to address the questions of whether the Cambrian and Ordovician radiations are separate events, or whether the latter is a continuation of the former, and what ecosystem restructuring occurred during the Ordovician. More generally, my main research interests include the taphonomy of exceptionally preserved fossils, metazoan origins and early evolution, and, in particular, arthropod biology. 

Graduate students

Ross Anderson

I am interested in the co-evolution of life and environments. I plan to investigate the relationship between Earth’s physical, chemical, and biological records through geologic time. Physical features of sedimentary rocks and biogeochemical signatures provide evidence of paleoenvironments, allowing us to learn how Earth has changed. I will explore how environmental proxies correlate with changing morphologies and inferred physiologies of fossils, to further understand how life and environments have evolved together.  To date my research has centered on the Neoproterozoic Era (1000-542 Ma), a period that saw large perturbations in both environment and biology. In particular, I have worked on probable new records of eukaryotic diversity within the Scottish Dalradian Supergroup.  I have recently initiated new projects in southwestern Mongolia and Scotland using experimental, analytical and field methods to investigate taphonomy of eukaryotic microfossils during both the Neoproterozoic Era and during the Cambrian Period when biomineralising forms diversified. Understanding the preservational biases enables us to reconstruct patterns of diversity temporally with respect to environmental change and to refine biostratigraphy of these intervals.  Other areas of active research include the visual system of Silurian eurypterids and biological controls on modern ooid formation.

Liz Clark

My research is centered on the study of echinoderm morphology to elucidate the evolutionary history of the group in light of its vast biodiversity, both extant and within the fossil record. I am currently working on understanding the movement capabilities and locomotion of Paleozoic ophiuroids and stylophorans by studying specific aspects of their morphology and using modern analogues. When this study of functionality is put within an evolutionary and ecological context, we will be able to better understand the history of the echinoderm clade. In addition, the study of novel forms of locomotion used by these enigmatic groups may have broader practical applications.

Emma Locatelli

My research interests lie in taphonomy, specifically decay and diagenesis in the formation of plant fossils. Fossil plants aid in the reconstruction of ancient environments, climates, and the evolutionary trajectories of major plant lineages.  Understanding the taphonomic filters that affect the formation of plant assemblages is critical to interpreting the information held within the fossils. For my doctoral research I am exploring different aspects of exceptional plant preservation, using fossil-based and experimental approaches. My thesis projects explore: An exceptionally preserved flora from New Caledonia; differential decay rates of land plants (bryophytes + tracheophytes) as an initial control on the plant fossil record; the role of clay minerals in the preservation of leaves in coarser grained sandstone (e.g. Dakota Sandstone); and the role of decay in promoting silicification.

Tory McCoy

My research focuses on exceptional fossilization within carbonate concretions.  In particular, I am investigating how the process of concretion formation affects decay and mineralization to promote soft tissue preservation.  This includes statistical analyses of data from the literature on concretion sites, geochemical analyses of fossiliferous concretions, and laboratory experiments to test how some of the factors affecting concretion formation impact decay and mineralization.  I am currently studying the Mazon Creek concretionary Lӓgerstatten.  

Chris Whalen

I am primarily interested in macroevolution and systematics, both vertebrate and invertebrate.  I study the Nektonic Revolution and the Late Devonian Biodiversity Crises (the Kellwasser and Hangenberg events), which profoundly and permanently altered the state of marine ecosystems.  The Devonian (419-359 Ma) saw the rapid colonization of the water column by metazoans, especially vertebrates and cephalopods.  The period has been called the “Age of Fishes” owing to the great diversity of jawed-vertebrates (gnathostomes), including the extant chondrichthyans (cartilaginous fishes) and osteichthyans (boney fishes) and the extinct placoderms (armored fishes) and acanthodians (spiny sharks); however, this period also saw the diversification of the extremely successful ammonoid and nautiloid cephalopods.  These lineages then severely declined during the crises that mark the periods’ climax, with the previously dominant placoderms completely eradicated.  I am investigating the phylogenetic interrelationships of Paleozoic ammonoids and early gnathostomes (with a focus on placoderms and acanthodians) as this information is critical for a proper understanding of the interesting and significant changes that occurred during the Devonian.  In an unrelated project I am also investigating modern squids and in the past I studied woolly mammoths.

Recent former students and postdoctoral associates

Arnaud Bignon

My work is based mainly on Devonian trilobites. These charming fossils allow me to work on different topics: i. Thanks to the numerous instars preserved in the fossil record, we know the ontogeny of trilobites very well. Comparison of the ontogenetic trajectories of different species from statistical shape analyses is fundamental to establishing the importance of developmental modifications to evolutionary processes. ii. Trilobites allow the relationship between environmental changes and fluctuations in biodiversity to be explored. My research focuses on the effects of the expansion of coral reefs on trilobite communities and trophic webs. iii. Presently, I am interested in the hydrodynamic functions of exoskeleton shape. I simulate the flow structure from Computational Fluid Dynamics in order to explain developmental modifications and/or the presence of particular structures. The objectives of these different research activities are to elucidate the influence of the environment on speciation and how evolution responds to environmental change.  Arnaud Bignon is now a postdoc at Universidad Nacional de Córdoba, Argentina.

Michelle Casey

My research focuses on the impact of eutrophication on the molluscan predator-prey ecology of Long Island Sound. To this end, I use several different methods including stable isotopes of nitrogen and carbon to investigate trophic position and diet, predation traces such as drill-holes and repair scars to examine predation intensity, and comparisons of the living and dead communities to examine ecological disturbance. I also work with a combination of modern and archaeological shell material in order to establish a pristine, pre-anthropogenic ecological baseline. Michelle Casey is now Assistant Professor at Murray University in Kentucky.

Simon Darroch

I am currently pursuing two main research directions: 1) the paleoecology and evolution of early animal communities, and how they affected sedimentary environments and ocean structure; and 2) the impact of mass extinctions on ecosystem structure and function, and how these lessons help to interpret present-day patterns of diversity loss.

1) The Ediacaran-Cambrian transition is a critical interval in the history of life, marking the explosive radiation of complex animals that have since dominated the surface of the planet, with the concurrent disappearance of enigmatic Ediacaran organisms.  I am working on Ediacaran sections in central and southern Namibia, where both latest Ediacaran and earliest Cambrian rocks are exposed in unparalleled volume and lateral extent, making this is an ideal area for investigating questions in Ediacaran-Cambrian geobiology.

2) Most analyses of mass extinctions have neglected the spatial dimensions of diversity change. One of the most fundamental biogeographic patterns is beta diversity, which describes variation in taxonomic composition across space. Quantifying beta diversity is central to understanding changes in the spatial distributions of species, and underpins much of conservation theory and practice. Most recently I have been investigating the responses of beta diversity to pulses of Ordovician-Silurian extinction at local, regional, and global scales, with a view to building predictive models for current/future biodiversity loss.

Simon Darroch is now Assistant Professor at Vanderbilt University in Nashville, Tennessee.

Una Farrell

My research focuses on the paleoecology and taphonomy of sites of exceptional preservation from the Late Ordovician Taconic Foreland Basin of Upstate NY. Beecher’s Trilobite Bed, near Rome NY, is a locality known for the preservation of trilobite soft-tissues in pyrite. Recent fieldwork has led to the discovery of multiple new sites with similar preservation in the same depositional basin, indicating that conditions for pyritization occurred multiple times. I am particularly interested in assessing oxygen levels in the water column and determining the diagenetic environment in which the trilobites and other organisms were preserved. The project includes microstratigraphical logging, sampling and paleontological analyses in addition to geochemical techniques for determining paleoenvironmental conditions, such as analyses of iron systematics, sulfur isotopes and trace element concentrations.  Una Farrell is now Collections Manager for Invertebrate Paleontology at the University of Kansas, Lawrence. 

Carolin Haug

The goal of my research project at Yale is the elucidation of the evolution of the raptorial apparatus of stomatopods, or mantis shrimps. These impressive predators possess a highly derived morphology compared to other malacostracan crustaceans and the eumalacostracan ground pattern. Yet, this derived morphology is bridged by various fossil representatives reaching back into the Carboniferous. Material comes, e.g., from the famous localities Mazon Creek and Bear Gulch. In addition to stomatopods, I investigate other arthropod taxa with comparable raptorial appendage morphologies, for example, Hoplostraca or Thylacocephala. These comparative studies are aimed at providing insight into the selective pressures leading to similar raptorial morphologies and lifestyle. My studies are based on the application of sophisticated imaging techniques that provide access to details inaccessible by conventional methods, e.g., fluorescence microscopy or stereo photography.  Carolin Haug is now Research Associate at Ludwig Maximilians University, Munich.

Joachim Haug

My field of research is referred to as palaeo-evo-devo. This research approach equals the intersection of the fields of developmental genetics, larval biology, comparative morphology, phylogenetic systematics and paleobiology. The main goals of such an approach are contributing to our understanding of evolution, diversification, and ecology by investigating the developmental patterns of fossil organisms. The group I am focusing on is Arthropoda (sensu lato). My approach demands for exceptionally preserved fossils, with fine morphological details such as limbs, eyes, details of the feeding setation, but also including sequences of developmental stages. Therefore, I work on fossils from deposits such as ‘Orsten’, Solnhofen, Chengjiang or Mazon Creek. During my project in Yale I am focusing on fossils from the famous Burgess Shale. A major part of the work includes developing new concepts for combining knowledge from so many different research fields into a cohesive theoretical framework, but also the presentation of such knowledge. As one aspect, I reconstruct the fossils I am studying as 4D virtual computer models, i.e., three-dimensional models of a series of developmental stages. Joachim Haug is now Postdoctoral Fellow at Ludwig Maximilians University, Munich.

Thomas Hegna

Arthropods are an incredibly diverse and successful group of organisms comprising over three-fourths of all known fossil and living species. Despite their ubiquity, many large questions remain about the interrelationships between and within the major clades of arthropods. My project aims to synthesize data from the fossil record, living animals and molecular phylogenetics to reconstruct the history of a peculiar group of crustaceans: the branchiopods (including tadpole shrimp, fairy shrimp, clam shrimp and water fleas). This group is of particular interest due to their hypothesized phylogenetic proximity to the origin of the hexapods and their early invasion of freshwater ecosystems, which may have been a key step toward terrestrialization. Ultimately this work will contribute to a better understanding of the phylogeny of Crustacea and its relationship to the Hexapoda. Thomas Hegna is now an Assistant Professor at Western Illinois University. 

Richard Krause

Differential preservation is always a concern for paleontologists. Even organisms with easily preserved hard parts, such as calcitic brachiopods, can exhibit a wide range of preservational styles depending on the interplay of a number of extrinsic and intrinsic factors. This raises the possibility that nearly identical faunas could appear to have highly divergent characteristics if subjected to different diagenetic histories. Using the Schuchert Brachiopod Collection of the Peabody Museum, I am working toward a more detailed understanding of temporal fluctuations in preservational style, and quantifying the effect that differential preservation has on our understanding of diversity, abundance, and size in brachiopod faunas. Richard Krause is now a Research Assistant in the Department of Paleontology, Institute of Earth Sciences, Johannes Gutenberg University, Mainz, Germany. 

Isabelle Kruta

I work on ammonites and other cephalopods and my main interest is on feeding structures (buccal mass elements), their function and their use for reconstructing ammonite feeding habits as well as phylogenies. In order to do so I work on elements found in situ using CT scans as well as Synchrotron light techniques, but also on elements found ex situ in order to work on morphological and microstructural variability. I also work on other ammonite’s related structures that can be found inside the body chamber. The aim of these studies is to reconstruct the paleobiology and paleoecology of ammonites in order to do synecological studies and establish the role and importance of this fossil group in Mesozoic communities. Isabelle Kruta holds a temporary professorship at University of Paris 6.

Marc Laflamme

My research interests lie in the classification and preservation of the Ediacara biota, the oldest large and complex organisms in the rock record. These globally-distributed soft-bodied organisms abruptly appear in the fossil record some 578 million years ago, and represent the dominant members of early ecosystems up until the Cambrian explosion of animals. My research focuses on the enigmatic Rangeomorphs and Erniettomorphs, which likely represent extinct lineages on par with animals and plants. I have used traditional and landmark-based morphometric techniques to study the growth and differentiation in closely related species, and recently applied modeling techniques to evaluate the likely feeding strategies employed by these enigmatic organisms.
My present research focuses on the taphonomic pathways that allowed for the preservation of soft-bodied Ediacara biota in coarse sediments. Environmental scanning electron microscopy (ESEM) is being used to study the chemical differentiation found in Ediacaran preservational settings. Marc Laflamme is now Assistant Professor in the Department of Geology, University of Toronto, Mississauga.

Maria McNamara

I am interested in fossil preservation, in particular, the exceptional preservation of non-biomineralised ‘soft’ tissues (e.g. skin, muscle, cuticle) in the fossil record. I use fossil-based and experimental approaches to understanding how such soft-bodied fossils are preserved - their taphonomy. My previous research on the taphonomy of exceptionally preserved higher vertebrates (i.e., amphibians, reptiles, birds and mammals) focused on processes of decay, skeletal disarticulation, and soft tissue preservation (as mineralized or organic remains). I am currently working on the preservation of structural colour in the fossil record, primarily in insects. I am especially interested in the fidelity of preservation, and the functional implications, of the colour. My research on vertebrate and invertebrate taphonomy is stimulated, and connected, by the fundamental need to elucidate the various controls upon exceptional preservation and thus to assess the fidelity of the fossil record. Maria McNamara is now Lecturer in Geology at University College, Cork.

Jakob Vinther

I work on the early evolution of molluscs and annelids as part of my PhD thesis. This involves description of exceptionally preserved fossils as well as reconstructing the evolutionary relationships using molecular biological techniques. My aim is to understand how phylogenies and fossils can illustrate morphological evolution of bodyplans.
I am also interested in taphonomy, especially preservation of melanin and I am working on interpreting original colors of fossil birds and their stem groups.  Jakob Vinther is now a lecturer in the Schools of Earth Sciences and Biological Sciences, University of Bristol, U.K.

Amelinda Webb

Broadly speaking, my research interest is in Phanerozoic ecology, although I prefer to work in the Paleozoic and the modern (as an analogue). My thesis focuses on developing and implementing methods for quantitatively measuring the ecologic response of marine invertebrate communities to major environmental changes, specifically during mass extinction events (Ordovician-Silurian and Devonian). Various other projects, past and present, include: the ecology of encrusting organisms on Devonian brachiopods, foraging strategy in Zoophycus burrows, predation on modern and Carboniferous brachiopods and molluscs, biomineralization in brachiopods and molluscs related to the repair of non-fatal predation damage, using morphology to detect competition between Carboniferous and Permian brachiopods, ecological impact of rapid global warming events such as the Paleocene-Eocene thermal maximum, and biotic response of modern organisms to different rates and magnitudes of environmental disturbances. Amelinda Webb is now Izaak William Killam Memorial Postdoctoral Fellow at the University of Alberta, Edmonton.

Jo Wolfe

My dissertation research addresses the origins of arthropod diversity, especially the evolution of segmentation and appendage development. This includes exploring the phylogenetic relationships between the major clades of arthropods: chelicerates, crustaceans, hexapods, myriapods, and extinct groups. I am comparing molecular vs. morphological data (including fossils from diverse Paleozoic Lagerstätten), and parsimony vs. other model-based approaches. I will be applying data on developmental gene expression patterns across taxa to make inferences about mechanisms of limb evolution in the Cambrian explosion. Jo Wolfe is now a postdoc at MIT.