Updated geology and vertebrate paleontology of the Triassic Ntawere Formation of northeastern Zambia, with special emphasis on the archosauromorphs

ABSTRACT

The two vertebrate fossil assemblages from the ?Middle Triassic Ntawere Formation have been known since the 1960s, but little new work has been done since the description of novel taxa in the 1960s and 1970s. Three recent field seasons have increased vertebrate diversity in the upper Ntawere assemblage and expanded biostratigraphic connections between the lower and upper Ntawere assemblages and assemblages in fossiliferous basins across southern Pangea. The upper Ntawere contains hybodontoid sharks, ptychoceratodontid lungfish, large- and small-bodied stereospondyl amphibians (Cherninia, ‘Stanocephalosaurus,’ Batrachosuchus, a new taxon), stahleckeriid dicynodonts (Sangusaurus, Zambiasaurus), traversodontid and trirachodontid cynodonts (Luangwa, a new species, Cricodon), and at least four archosauromorphs, including a large loricatan pseudosuchian, a shuvosaurid poposauroid, and silesaurid dinosauriforms (Lutungutali), whereas the lower Ntawere contains the cynodonts Cynognathus and Diademodon and species of the dicynodont Kannemeyeria. The lower and upper Ntawere assemblages have been correlated with the middle and upper subzones of the Cynognathus Assemblage Zone of the Karoo Basin, South Africa, into a network of connections between assemblages in modern day Tanzania, Argentina, Brazil, Namibia, Antarctica, and India. Although lower Ntawere correlations are reinforced by the occurrence of Cynognathus, new observations from the upper Ntawere, in combination with field work in Tanzania, Namibia, and Brazil, have shifted the geographic focus of biostratigraphic connection away from the Karoo later in the Triassic. A recent radiometric date from Argentina from below the horizon correlated with both the Karoo and the lower Ntawere places these, and all higher assemblages, into the Carnian Stage of the Late Triassic.

Citation for this article: Peecook, B. R., J. S. Steyer, N. J. Tabor, and R. M. H. Smith. 2018. Updated geology and vertebrate paleontology of the Triassic Ntawere Formation of northeastern Zambia, with special emphasis on the archosauromorphs; pp. 8–38 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

ACKNOWLEDGMENTS

We would like to thank the team members of the 2009, 2011, and 2014 expeditions to the Luangwa Valley, including C. A. Sidor (University of Washington, Seattle), K. D. Angielczyk (Field Museum of Natural History, Chicago), S. J. Nesbitt (Virginia Tech, Blacksburg), K. Mwamulowe and J. Museba (National Heritage Conservation Commission, Lusaka), S. Tolan (Chipembele Wildlife Education Trust, Mfuwe), A. Goulding (Lusaka), R. Whatley (Columbia College, Chicago), and J. Menke (Elizabeth Glaser Pediatric AIDS Foundation, Lusaka). The National Heritage Conservation Commission of Zambia graciously provided permits for the collection and temporary export of fossils. Research on the Triassic vertebrate fauna of Zambia has been supported by the National Geographic Society (grant 8571-08 to J. S. Steyer and 8962-11 to C. A. Sidor), The Grainger Foundation and Field Museum/IDP Foundation, Inc. African Partners Program (to K. D. Angielczyk), and the National Science Foundation (EAR-1337569 to C. A. Sidor; EAR-1337291 to K. D. Angielczyk; EAR-1336986 to P. Roopnarine; Doctoral Dissertation Improvement Grant 1051097 to B.R.P.). We thank P. Barrett, L. Steel, and A. Milner (NHMUK); B. Rubidge, S. Jirah, and B. Zipfel (BP); and T. and M. Kemp (Oxford) for hospitality and help with Ntawere specimens in collections. We thank especially A. Huttenlocker (University of Southern California, Los Angeles), M. Whitney (University of Washington), and J. Lungmus (University of Chicago, Chicago) for providing interpretive and technical help with histology, as well as the attendees of the 2nd International Symposium for Paleohistology held in Bozeman, Montana, in 2013. B.R.P. was supported by a National Science Foundation Graduate Research Fellowship during the writing of the manuscript and the 2011 expedition. We thank SVP memoirs editor R. Irmis as well as reviewers W. Parker and J. Fröbisch for improving the manuscript.

Additional information

Funding

National Geographic Society 8571-08,8962-11; National Science Foundation 1501097,EAR-1336986,EAR-1337291,EAR-1337569