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    Published: March 16, 2011

    Paleontological Research in Tanzania

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

    Introduction

    The Permian and Triassic periods (approximately 299 Mya to 199 Mya) are critical times in Earth history. Among the important events that occur during this interval are a major diversification of ancient mammal relatives called non-mammalian synapsids, a transition between from an ice-house global climate regime to a greenhouse climate regime, the largest mass extinction in Earth history, the origin of mammals, and the origin and early diversification of dinosaurs. In 2007 and 2008 Field Museum researchers Ken Angielczyk and Bill Simpson were part of an international team of scientists that traveled to the Ruhuhu Basin in southern Tanzania to collect fossils and geological data from Upper Permian and Lower Triassic rocks to gain new insight into the causes of and recovery from the end-Permian mass extinction in terrestrial vertebrate-dominated communities.

    | Tanzania Map | | Map showing location of the Ruhuhu Basin. Courtesy of C. Sidor. |

    The Ruhuhu Basin

    The Ruhuhu Basin is an ancient rift basin in which Permian and Triassic sedimentary rocks were deposited. Of particular interest to our team are the rocks of the Permian-age Ruhuhu Formation and Usili Formation, and the Triassic-age Manda beds because these rocks preserve fossils of terrestrial vertebrates.

    | | | Lithostratigraphy of the Ruhuhu Basin. Formations of interest are highlighted. Modified from Wopfner (2002). Courtesy of C. Sidor. |

    Fossils were first discovered in the Ruhuhu Basin by Gordon. Stockley in the 1930's. Subsequent collections of fossils were made in the mid-1930's by Rex Parrington of Cambridge University and Ernst and Maria Nowack, who were jointly sponsored by Cambridge University and the University of Tübingen. These collections showed that the Permian and Triassic faunas of the Ruhuhu Basin included many synapsids, as well as rarer reptiles and amphibians, and were similar to those known from the Karoo Basin of South Africa. In 1963, an expedition sponsored by University College London and the British Museum of Natural History (now The Natural History Museum) collected additional fossils from the basin, including new synapsids and archosaurs (the group that includes dinosaurs, birds, and their relatives). After 1963, no large collections of vertebrate fossils were made from the Ruhuhu Basin until our team began our research in 2007.

    Fossils of the Ruhuhu Formation

    Although there are older reports of plant fossils from the Ruhuhu Formation, the first report of vertebrate fossils was made by members of the 1963 expedition (Attridge et al., 1964; Cox, 1964; 1991; Cruickshank, 1986; Gay and Cruiskshank, 1999).

    | | | Dinocephalian tooth discovered in the Ruhuhu Formation. Photo by W. Simpson. |

    These specimens have not yet been formally described, and our team questioned whether they originated in the Ruhuhu Formation, or the overlying Usili Formation (Sidor et al., 2010). In 2008, our team discovered fragmentary fossils of dinocephalian synapsids, anomodont synapsids, and temnospondyl amphibians in the Ruhuhu Formation. The dinocephalian specimens are especially important because they are the first members of this group to be found in Tanzania, and they suggest a Middle Permian age for the Ruhuhu Formation (Simon et al., 2010). The anomodont and amphibian material is still currently under study.

    Fossils of the Usili Formation

    | | | Skull of the anomodont synapsid "Dicynodon" huenei found in the Usili Formation. Photo by K. Angielczyk |

    The great majority of Permian tetrapod fossils collected by previous workers were found in the Usili Formation. The fauna is dominated by synapsids, especially anomodonts and gorgonopsians, although therocephalians and cynodonts are rarer components of the fauna. Pareiasaurs (herbivorous armored reptiles) also are present, as well as a distinctive armored amphibian called Peltobatrachus.

    Our team collected a large number of anomodont fossils in the Usili formation, including at least one new species. We also discovered the first burnetiamorph (a type of carnivorous synapsid characterized by bony lumps on the skull) from Tanzania (Sidor et al., 2010), new specimens of the cynodont Procynosuchus (Weide et al., 2009), pareiasaurs, large saber-toothed gorgonopsians, and fragmentary specimens of Peltobatrachus.

    | | | Sterling Nesbitt shows off a canine tooth from a large gorgonopsian synapsid that he just found in the Usili Formation. Photo by R. Smith. |

    The Usili Formation tetrapod fauna is similar to coeval faunas in the Karoo Basin of South Africa in being dominated by synapsids, but also differs in having several endemic species and a mixture of broadly-distributed species that do not co-occur in South Africa.

    Fossils of the Manda Beds

    | | | Skull of the cynodont synapsid Scalenodon angustifrons found in the Lifua Member. Photo by K. Angielczyk. |

    The Manda beds are of Middle Triassic age (approximately 240 Mya),and consist of two named members, the Kingori Sandstone and the Lifua Member. Very few fossils have been collected from the Kingori Sandstone, and our team has spent little time working in this unit. The Lifua Member is much richer, with previous workers recovering a mixture of anomodont and cynodont synapsids, as well as several archosaurs and rhynchosaurs (a group of herbivorous reptiles related to archosaurs). Our team collected a few fragments of a very large amphibian, some rhynchosaur specimens, and some anomodont material, mostly representing an animal called Sangusaurus. Cynodont specimens also are common at certain localities, and we have representatives of at least six species. Most importantly, we discovered several archosaurs, including relatives of dinosaurs and crocodiles. To date, we have described one of these archosaurs, the dinosaur relative Asilisaurus kongwe (Nesbitt et al., 2010).

    | | | Artist's reconstruction of Asilisaurus kongwe (foreground). The sail-backed archosaur in the background is Hypselorhachis mirabilis. Image by M. Donnelly. |

    Asilisaurus is a small, lightly built herbivore, but it is one of the closest relatives of dinosaurs known. Furthermore, its presence in the Middle Triassic implies that dinosaurs must have originated by this time, which is about ten million years earlier than previously thought. The other archosaurs are under study, and when combined with previously described material, they suggest that the Middle Triassic fauna of Tanzania had a much greater diversity of archosaurs than contemporary faunas in South Africa.

    The End-Permian Mass Extinction

    Approximately 252 Mya, at the end of the Permian Period , terrestrial and marine ecosystems were struck by the largest mass extinction in Earth history. Although the exact cause of the extinction is still debated, it appears likely that massive volcanic eruptions in Siberia were the ultimate cause, with global warming and changes in ocean chemistry as important kill mechanisms for marine and terrestrial animals and plants. Our picture of how terrestrial vertebrate faunas were affected by this event and how they recovered primarily comes from the Karoo Basin of South Africa and the fore-Ural region of Russia. A major goal of our work in Tanzania is to document the Permo-Triassic transition in the Ruhuhu Basin for comparison with the better-studied South African and Russian records.

    Although there appears to be a hiatus in the early Triassic fossil record in the Ruhuhu Basin, we can make inferences about the effects of the extinction by comparing the Late Permian Usili Formation fauna to that known from the Lifua member. The Usili Formation fauna is quite comparable to that seen in South Africa, with synapsids dominating in both diversity and abundance. In addition, the synapsids in both places appear to have been strongly affected by the extinction, because many groups become completely extinct, and even the survivors show patterns of turnover (i.e., replacement of older species by new species). Despite this apparent similarity in the effects of the extinction, the recovery process in South African and Tanzania appears to have proceeded differently. South African faunas in the Early and Middle Triassic consist of a fairly balanced mix of synapsids, reptiles, and amphibians, with only a few species of archosaurs present. In contrast, a much greater diversity of archosaurs is present in Tanzania in the Middle Triassic, and these species show greater signs of ecological differentiation than their South African contemporaries (which were all carnivores). Synapsids are relatively common in Tanzania as well, but amphibians and small reptiles are rare to completely absent. We are now investigating why the recovery process proceeded in different ways in Tanzania and South Africa, and are also studying Permian and Triassic communities in Zambia to see whether they more closely resemble the patterns observed in Tanzania or South Africa.

    Our Fieldwork Teams

    | | | The 2007 Ruhuhu Basin Fieldwork Team: (left to right): Ken Angielczyk, Sterling Nesbitt, Roger Smith, Linda Tsuji, Christian Sidor, Anthony Tibaijuka. Photos courtesy of C. Sidor. |

    | | | The 2008 Ruhuhu Basin Fieldwork Team: (back row, left to right): Linda Tsuji, Ken Angielczyk, Sebastien Steyer, Bill Simpson, Christian Sidor; (front row, left to right) Laurent Nampunju, Mohammed (our excellent cook), Roger Smith. Photo courtesy of R. Smith. |

    I Dig Tanzania!

    | | | Students in New York City conduct their virtual fossil dig in Teen Second Life. Photo courtesy of Global Kids. |

    During the 2008 field season, our team collaborated with The Field Museum's Education Department, the Biodiversity Synthesis Center, and Global Kids on a digital learning pilot program called “I Dig Tanzania!” Through this program, groups of high school students followed the progress of our fieldwork in real time by watching short videos we filmed and uploaded by satellite internet connection, and by talking to us on satellite phone calls. The students also used the 3D virtual world Teen Second Life to participate in a virtual fossil dig of their own, which had activities designed to replicate various aspects of our research, and to build virtual museums exhibits detailing the results of their work. In addition to learning about science, the students studied Tanzanian history, politics, and culture, and received behind-the-scenes tours at museums. I Dig Tanzania! was made possible by funding from The John D. and Catherine T. MacArthur Foundation.

    Publications

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    Our team has published several journal articles and abstracts based on our research in the Ruhuhu Basin. PDF copies of the following papers are available on request.

    Journal Articles

    Simon, R. V., Sidor, C. A., Angielczyk, K. D., and Smith, R. M. H. 2010. First record of a tapinocephalid (Therapsida: Dinocephalia) from the Ruhuhu Formation (Songea Group) of southern Tanzania. Journal of Vertebrate Paleontology 30: 1289-1293.

    Sidor, C. A., Angielczyk, K. D., Weide, D. M., Smith, R. M. H., and Tsuji, L. A. 2010. Tetrapod fauna of the lowermost Usili Formation (Songea Group, Ruhuhu Basin) of southern Tanzania, with a new burnetiid record. Journal of Vertebrate Paleontology 30: 696-703.

    Nesbitt, S. J., Sidor, C. A., Irmis, R. B., Angielczyk, K. D., Smith, R. M. H., and Tsuji, L. A. 2010. Ecologically distinct dinosaurian sister-group indicates early diversification of Ornithodira. Nature 464: 95-98.

    Weide, D. M., Sidor, C. A., Angielczyk, K. D., and Smith, R. M. H. 2009. A new record of Procynosuchus delaharpeae (Therapsida: Cynodontia) from the Upper Permian Usili Formation, Tanzania. Palaeontologia africana 44: 21-26.

    Angielczyk, K. D., Sidor, C. A., Nesbitt, S. J., Smith, R. M. H., and Tsuji, L. A. 2009. Taxonomic revision and new observations on the postcranial skeleton, biogeography, and biostratigraphy of the dicynodont genus Dicynodontoides, the senior subjective synonym of Kingoria (Therapsida, Anomodontia). Journal of Vertebrate Paleontology 29: 1174-1187.

    Abstracts

    Angielczyk, K. D., Sidor, C. A., Smith, R. M. H., Nesbitt, S. J., Steyer, J.-S., and Fröbisch, J. 2009. Permian and Triassic Tetrapod Faunas and Paleoenvironments of Tanzania and Zambia: Implications for the Permo-Triassic Transition. Geological Society of America Abstracts with Programs 41 (7): 242.

    Angielczyk, K. D., Sidor, C. A., Smith, R. M. H., Steyer, J.-S., and Gostling, N. J. 2009. A re-evaluation of the dicynodonts (Therapsida, Anomodontia) of the Permian Ruhuhu Formation (Songea Group, Ruhuhu Basin), Tanzania. Journal of Vertebrate Paleontology 29 (supplement to 3): 55A.

    Sidor, C. A., Angielczyk, K. D., Hopson, J. A., Kammerer, C. F., and Smith, R. M. H. 2009. New information about cynodonts from the Middle Triassic Manda Beds (Ruhuhu Basin) of Tanzania. Journal of Vertebrate Paleontology 29 (supplement to 3): 181A.

    Angielczyk, K. D., Sidor, C. A., Tsuji, L. A., Nesbitt, S. J., and Smith, R. M. S. 2008. The Permo-Triassic dicynodont fauna of the Ruhuhu Basin, Tanzania: new discoveries and their implications. Journal of Vertebrate Paleontology 28 (supplement to 3): 46A.

    Sidor, C. A., Angielczyk, K. D., Hospon, J. A., Nesbitt, S. J., and Smith, R. M. H. 2008. New vertebrate fossils from the Permo-Triassic Ruhuhu Basin of Tanzania. Journal of Vertebrate Paleontology 28 (supplement to 3): 142A-143A.

    Weide, D. M., Sidor, C. A., Angielczyk, K. D., and Smith R. M.H. 2008. A new record of Procynosuchus delaharpeae (Therapsida: Cynodontia) from the Upper Permian Usili Formation (Ruhuhu Basin), Tanzania. Journal of Vertebrate Paleontology 28 (supplement to 3): 158A.

    Acknowledgments

    Our fieldwork in 2007 was funded by National Geographic (CRE #7587-05 to C. A. Sidor), the National Science Foundation (NSF Graduate Fellowship to S. J. Nesbitt; NSF DBI-0306158 to K. D. Angielczyk), and the Evolving Earth Foundation (Evolving Earth Foundation grant to S. Nesbitt). Our fieldwork in 2008 was funded by The Grainger Foundation (grant to K. D. Angielczyk), and I Dig Tanzania! was funded by The John D. and Catherine T. MacArthur Foundation. Our research in Tanzania is made possible by the support of the Tanzanian Commission for Science and Technology, the Tanzanian Ministry of Natural Resources and Tourism, and Dr. Charles Sanaane (University of Dar es Salaam).

    References Cited

    Attridge, J., Ball, H. W., Charig, A. J., Cox, C. B. 1964. The British Museum (Natural History)--University of London Joint Palaeontological Expedition to Northern Rhodesia and Tanganyika, 1963. Nature 201: 445-449.

    Cox, C. B. 1964. On the palate, dentition, and classification of the fossil reptile Endothiodon and related genera. American Museum Novitates 2171: 1-25.

    Cox, C. B. 1991. THe Pangaea dicynodont Rechnisaurus and the comparative biostratigraphy of Triassic dicynodont faunas. Palaeontology 34:767-784.

    Cruickshank, A. R. I. 1986. Biostratigraphy and classification of a new Triassic dicynodont from East Africa. Modern Geology 10: 121-131.

    Gay, S. and Cruickshank, A. R. I. 1999. Biostratigraphy of the Permian tetrapod faunas from the Ruhuhu Valley, Tanzania. Journal of African Earth Sciences 29: 195-210.

    Wopfner, H. 2002. Tectonic and climatic events controlling deposition in Tanzanian Karoo basins. Journal of African Earth Sciences 34: 167-177.

    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.