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Published: July 24, 2012

Brazil 2012 Fieldwork Diary Entry 15: The Evolutionary Process of Science

Ken Angielczyk, MacArthur Curator of Paleomammalogy and Section Head, Negaunee Integrative Research Center

An idiosyncrasy of traveling to and from Teresina is that many of the flights arrive and depart between about midnight and 4:00am. So, it's currently 3:00am and I'm in the departure lounge waiting for my flight to São Paulo, where I will pick up my flight back to the U.S. Most of my collaborators have already left, so the trip is nearly completely over. Over the last three days, though, we've spent time doing some sorting and comparisons of the specimens we collected this year, as well as thinking about the next steps in this particular project.

Prospecting for fossils at an outcrop near Nova Iorque. Photo by Ken Angielczyk.

An idiosyncrasy of traveling to and from Teresina is that many of the flights arrive and depart between about midnight and 4:00am. So, it's currently 3:00am and I'm in the departure lounge waiting for my flight to São Paulo, where I will pick up my flight back to the U.S. Most of my collaborators have already left, so the trip is nearly completely over. Over the last three days, though, we've spent time doing some sorting and comparisons of the specimens we collected this year, as well as thinking about the next steps in this particular project.

One of the things that I've found to be a constant in my time as a scientist is that science itself is an evolutionary process of sorts. Very few are the projects that end in exactly the way you would think when you embark on them. Instead, each new piece of data causes a rethinking of your previous ideas, your expectations for future results, and your thoughts about what the interesting and important parts of the project really are. Sometimes the changes are minor, but in other cases things can change fairly significantly as you go, and I consider it important that we as scientists be open to following the data wherever they may lead. In the case of our research in the Parnaíba Basin, I think our discoveries are leading us in a different direction than we thought when we first started collecting specimens last year, or even at the beginning of this trip, but the questions along the new path are equally promising.

As I noted previously, it seems increasingly unlikely that we will find fossil synapsids in the Pedra de Fogo Formation. Even though the rocks of the formation were formed at about the right time and in a seemingly well-situated place to preserve such fossils, the specific environments that were present in the basin apparently weren't conducive to synapsids living there (or at least leaving a fossil record for us). So even as work was proceeding this year, the importance of synapsids in our minds was diminishing as we were thinking about the meanings of the fossils we were finding and our new geological data.

Even though we did not find synapsids, we did discover a lot of animals that we think are either new species or new records of species known from elsewhere that were not thought to be present in the Parnaíba Basin. As a result, the assemblage of animals preserved in the Pedra de Fogo Formation seems to be much more diverse than previously appreciated. That's a nice result because we really don't have much information about what animals were living in central Pangaea during the Permian, and our work will help to fill in that gap. The geographically closest areas that preserve similarly-aged fossils are found in places like Morocco and Niger. There is little overlap between the animals present in those places and in the Parnaíba Basin, even though there seems to be similarities in the environments in which the animals were living. This might mean that the assemblages are of slightly different ages, or there might have been more differentiation among environments and the animals they supported than is often thought to be the case for Pangaea (where an animal could theoretically walk from Antarctica to Siberia).

With this in mind, I think a lot of our work on this project going forward will focus on the biogeographic implications of the specimens that we collected. For example, as we study our new amphibian specimens, it will be very interesting to see where their closest relatives are found. Do they represent southern range extensions for groups that are mainly known from the northern hemisphere, as seems to be the case for Prionosuchus plummeri? This could imply that the Parnaíba Basin did lie along an important dispersal corridor, even if synapsids didn't pass through the area. Likewise, how many species in the assemblage are endemic to the Parnaíba Basin (i.e., occur there and nowhere else), like Anisopleurodontis pricei? If many of the species are endemic, it could mean that the animals in the basin were relatively isolated for an extended period of time, giving them time to diverge from their close relatives living elsewhere. Or it might mean conditions in the basin were unusual, and animals living there were forced to adapt to them or become extinct. We'll see where the data lead us, and I'm happy that my collaborators and I will be able to follow them into unexplored territory.

It's time to get on the plane now. Hopefully I can get some sleep, and perhaps dream of an oasis in a sandy desert, surrounded by tree ferns, with a Prionosuchus lurking just below the water's surface, waiting for a breakfast-sized lungfish to swim by…

Ken Angielczyk
MacArthur Curator of Paleomammalogy and Section Head

I am a paleobiologist interested in three main topics: 1) understanding the broad implications of the paleobiology and paleoecology of extinct terrestrial vertebrates, particularly in relation to large scale problems such as the evolution of herbivory and the nature of the end-Permian mass extinction; 2) using quantitative methods to document and interpret morphological evolution in fossil and extant vertebrates; and 3) tropic network-based approaches to paleoecology. To address these problems, I integrate data from a variety of biological and geological disciplines including biostratigraphy, anatomy, phylogenetic systematics and comparative methods, functional morphology, geometric morphometrics, and paleoecology.

A list of my publications can be found here.

More information on some of my research projects and other topics can be found on the fossil non-mammalian synapsid page.

Most of my research in vertebrate paleobiology focuses on anomodont therapsids, an extinct clade of non-mammalian synapsids ("mammal-like reptiles") that was one of the most diverse and successful groups of Permian and Triassic herbivores. Much of my dissertation research concentrated on reconstructing a detailed morphology-based phylogeny for Permian members of the clade, as well as using this as a framework for studying anomodont biogeography, the evolution of the group's distinctive feeding system, and anomodont-based biostratigraphic schemes. My more recent research on the group includes: species-level taxonomy of taxa such as Dicynodon, Dicynodontoides, Diictodon, Oudenodon, and Tropidostoma; development of a higher-level taxonomy for anomodonts; testing whether anomodonts show morphological changes consistent with the hypothesis that end-Permian terrestrial vertebrate extinctions were caused by a rapid decline in atmospheric oxygen levels; descriptions of new or poorly-known anomodonts from Antarctica, Tanzania, and South Africa; and examination of the implications of high growth rates in anomodonts. Fieldwork is an important part of my paleontological research, and recent field areas include the Parnaíba Basin of Brazil, the Karoo Basin of South Africa, the Ruhuhu Basin of Tanzania, and the Luangwa Basin of Zambia. My collaborators and I have made important discoveries in the course of these field projects, including the first remains of dinocephalian synapsids from Tanzania and a dinosaur relative that implies that the two main lineages of archosaurs (one including crocodiles and their relatives and the other including birds and dinosaurs) were diversifying in the early Middle Triassic, only a few million years after the end-Permian extinction. Finally, the experience I have gained while studying Permian and Triassic terrestrial vertebrates forms the foundation for work I am now involved in using models of food webs to investigate how different kinds of biotic and abiotic perturbations could have caused extinctions in ancient communities.

Geometric morphometrics is the basis of most of my quantitative research on evolutionary morphology, and I have been using this technique to address several biological and paleontological questions. For example, I conducted a simulation-based study of how tectonic deformation influences our ability to extract biologically-relevant shape information from fossil specimens, and the effectiveness of different retrodeformation techniques. I also used the method to address taxonomic questions in biostratigraphically-important anomodont taxa, and I served as a co-advisor for a Ph.D. student at the University of Bristol who used geometric morphometrics and finite element analysis to examine the functional significance of skull shape variation in fossil and extant crocodiles. Focusing on more biological questions, I am currently working on a large geometric morphometric study of plastron shape in extant emydine turtles. To date, I have compiled a data set of over 1600 specimens belonging to nine species, and I am using these data to address causes of variation at both the intra- and interspecific level. Some of the main goals of the work are to examine whether plastron morphology reflects a phylogeographic signal identified using molecular data in Emys marmorata, whether the "miniaturized" turtles Glyptemys muhlenbergiiand Clemmys guttata have ontogenies that differ from those of their larger relatives, and how habitat preference, phylogeny, and shell kinesis affect shell morphology.

A collaborative project that began during my time as a postdoctoral researcher at the California Academy of Sciences involves using using models of trophic networks to examine how disturbances can spread through communities and cause extinctions. Our model is based on ecological principles, and some of the main data that we are using are a series of Permian and Triassic communities from the Karoo Basin of South Africa. Our research has already shown that the latest Permian Karoo community was susceptible to collapse brought on by primary producer disruption, and that the earliest Triassic Karoo community was very unstable. Presently we are investigating the mechanics that underlie this instability, and we're planning to investigate how the perturbation resistance of communities as changed over time. We've also experimented with ways to use the model to estimate the magnitude and type of disruptions needed to cause observed extinction levels during the end-Permian extinction event in the Karoo. Then there's the research project I've been working on almost my whole life.

Morphology and the stratigraphic occurrences of fossil organisms provide distinct, but complementary information about evolutionary history. Therefore, it is important to consider both sources of information when reconstructing the phylogenetic relationships of organisms with a fossil record, and I am interested how these data sources can be used together in this process. In my empirical work on anomodont phylogeny, I have consistently examined the fit of my morphology-based phylogenetic hypotheses to the fossil record because simulation studies suggest that phylogenies which fit the record well are more likely to be correct. More theoretically, I developed a character-based approach to measuring the fit of phylogenies to the fossil record. I also have shown that measurements of the fit of phylogenetic hypotheses to the fossil record can provide insight into when the direct inclusion of stratigraphic data in the tree reconstruction process results in more accurate hypotheses. Most recently, I co-advised two masters students at the University of Bristol who are examined how our ability to accurately reconstruct a clade's phylogeny changes over the course of the clade's history.

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