Published: July 23, 2012

Brazil 2012 Fieldwork Diary Entry 8: Finding Fossils from Space

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

In my previous entry, I noted the difficulties that sometimes accompany efforts to relocate historical fossil localities. Today, I would like to describe an instance when using a combination of the scientific literature and new technologies worked to help us find fossils.

Juan Cisneros, Domingas de Conceiçáo, and Martha Richter examine a newly discovered fossil shark spine. Photo by Ken Angielczyk.

In my previous entry, I noted the difficulties that sometimes accompany efforts to relocate historical fossil localities. Today, I would like to describe an instance when using a combination of the scientific literature and new technologies worked to help us find fossils.

One of the main scientific papers that we're using in our efforts is one published by Dr. Barry Cox and others in 1991. This paper describes fossils he and his collaborators found in the area near Pastos Bons and Nova Iorque in 1970 and 1972. In the paper they provided information on what level in the local rock sequence they found their fossils, as well as where they found them in terms of a distance from Pastos Bons along the road to Nova Iorque and a distance away from the road. Barry also graciously sent me some photos from his work in the area, so we have an idea of what the actual outcrops look like and how the fossils are exposed on the surface. Unlike most of the fossils we found in the quarry, which were still embedded in the surrounding rock, Barry's specimens were found loose on the surface.

Based on Roger Smith's work over the last few days, we now have a good idea of the local sequence of rocks (or stratigraphy) of the area, as well as how exposures of those rocks tend to be situated relative to local geographic features, such as ridges or river beds. So, our first step was to determine how the rocks Barry described fit into our picture of the local stratigraphy. Once we had done that, we could make a prediction about where exposures of those rocks might occur geographically.

To refine our prediction, we went onto Google Earth and examined satellite photos of the region near Nova Iorque. Working from areas that we had visited and in which we knew the rocks, we determined a general area where the target rocks were likely located. Then, we looked at the satellite images in detail to find exposures of rock in the area of interest. We also double-checked this location to see if it was about the right distance down the road and about the right distance from the road to correspond to Barry's fossil localities. Finally, we obtained latitude and longitude coordinates from Google Earth for the outcrops we could see. We entered these into our GPS receivers, and then it was off to the field.

It was just a short walk from the side of the road to the exposure, and our GPS receivers pointed the direction we needed to go to reach the outcrop. Within a few minutes of arriving, we had found a fossil shark spine. Things don't usually go quite this smoothly, but it does provide a good example of one of processes we use to reconstruct this kind of information and how things happen when everything goes right.

Fossil shark spine found loose on the surface of the outcrop we targeted using Google Earth. Note that the ornamentation of the spine is similar to one that we found a few days earlier in the quarry. Scale bar is in centimeters. Photo by Ken Angielczyk.

In addition to finding the shark spine and other fossils at the locality, this exercise was important for another reason. The preservation style of these fossils and how they appear on the surface is somewhat different than most of the fossils we have discovered so far on this trip and on our reconnaissance trip in 2011. So we now have a new search image to use for finding fossils in the area, and one that we think will be very useful. Just before we returned to our houses, we stopped at a similar outcrop to the one at which we found the shark spine that we visited briefly in 2011. We didn't find much last time, but with the new search image, we found some very exciting fossils. In particular, Jörg Fröbisch discovered a small piece of a lower jaw with two teeth that seems to belong to Prionosuchus plummeri, the large fossil amphibian known from the Parnaíba Basin. Although we've found other specimens that seem to belong to amphibians on this trip, this is the first one we can say with some certainty represents Prionosuchus. Tomorrow, our plan is to return to this area to see if we can find more because our searching was suspended on account of darkness.

Jaw fragment of the temnospondyl amphibian Prionosuchus plummeri. The photo is taken looking down at the two broken teeth. Scale bar is in centimeters. Photo by Ken Angielczyk.


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.