The Triassic Transition: Analyzing niche replacement between major clades of fossil vertebrates
Final Report Abstract
The transition between Permian (298.9–251.9 million years ago) and Triassic (251.9–201.3 million years ago) faunas represents one of the most extreme periods of turnover in animal history. The Permo-Triassic mass extinction resulted in a radical restructuring of terrestrial ecosystems, with replacement of assorted ‘archaic’ animal groups by a more modern fauna. Although this transition has been subject to extensive study, many questions concerning the dynamics of this turnover and its temporal and geographic extent remain. This project explored these issues in the context of the major group of terrestrial vertebrates, the amniotes. The Permo-Triassic mass extinction was a global catastrophe, but the preserved record of this event is strongly geographically biased, with the majority of information on amniote turnover derived from the Karoo Basin of South Africa. We studied Permian and Triassic amniote faunas globally, giving particular attention to historically understudied regions. In the course of this work we described ten new species of Permo-Triassic amniotes, including taxa from previously poorly understood assemblages in Brazil, India, and Russia. More than just naming new species, however, this research provided new information on faunal commonalities and variation across the Permo Triassic Earth. In some cases, we were able to show that ‘traditional’ patterns originally derived from Karoo data do hold at the broader scale and can be used to infer cosmopolitan trends. For example, our description of new sabre-toothed synapsids from Russia demonstrated that the same patterns of turnover observed between the major groups of Permian carnivores in South Africa also occurred in the northern hemisphere. By contrast, the Permian Brazilian record includes representatives of major synapsid groups unknown in South Africa in similar-aged deposits, indicating that global diversity estimates extrapolated from the latter are likely misleading. The shift between synapsid-dominated Permian amniote faunas and Triassic faunas, where increasingly the most abundant and diverse amniotes are archosauromorphs (dinosaurs, crocodiles, and their extinct relatives), is an important aspect of the Permo-Triassic transition. However, we have shown that this transition is not as straightforward as previously believed, and likely contains substantial geographical and even lower-level ecological variation. We found that the replacement of synapsids by archosaurs is not as complete as historically presented, with synapsids continuing to be important components of terrestrial communities even into the Late Triassic. Dicynodont synapsids, which were the dominant herbivores of the Permian and were decimated by the Permo Triassic extinction, not only survived into the Late Triassic but co-existed with large herbivorous dinosaurs, a group usually thought to arise only after dicynodont extinction. Looking at the Permian side of things, we also found that the characteristic ‘Triassic fauna’ (numerically dominated by archosauromorph reptiles and cynodont synapsids) is actually present in certain exceptional deposits prior to the Permo-Triassic extinction. In particular, we showed that the unique Permian fissure fillings from the Korbach locality in central Germany preserves a fauna typical of the Early Triassic in South Africa, suggesting that faunal turnover over the extinction boundary may correspond more closely with expansion and contraction of preferred habitats for the major amniote groups than hard extinction and origination points.
Publications
-
2018. Cranial anatomy of the gorgonopsian Cynariops robustus based on CT-reconstruction. - PLoS ONE 13(11): e0207367
Bendel, E.-M., Kammerer, C.F., Kardjilov, N., Fernandez, V. & Frobisch, J.
-
2018. Evolutionary rates of mid-Permian tetrapods from South Africa and the role of temporal resolution in turnover reconstruction. - Paleobiology 44: 347-367
Day, M.O., Benson, R.B.J., Kammerer, C.F. & Rubidge, B.S.
-
2018. Non-mammalian synapsids: the deep roots of the mammalian family tree. Chapter 2 (pp. 117-198) in Asher, R. & Zachos, F. (eds.) Handbook of Zoology: Mammmalia. Berlin, DeGruyter
Angielczyk, K.D. & Kammerer, C.F.
-
2018. The first skeletal evidence of a dicynodont from the lower Elliot Formation of South Africa. - Palaeontologia africana 52: 102-128
Kammerer, C.F.
-
2019. A new dicynodont (Anomodontia: Emydopoidea) from the terminal Permian of KwaZulu-Natal, South Africa. - Palaeontologia africana 53: 179-191
Kammerer, C.F.
-
2019. Cranial anatomy of the early cynodont Galesaurus planiceps and the origin of mammalian endocranial characters. - Journal of Anatomy 234(5): 592-621
Pusch, L., Kammerer, C.F. & Frobisch, J.
-
2019. Diversity patterns of nonmammalian cynodonts (Synapsida, Therapsida) and the impact of taxonomic practice and research history on diversity estimates. - Paleobiology 45(1): 56-69
Lukic-Walter, M., Brocklehurst, N., Kammerer, C.F. & Frobisch, J.
-
2019. Revision of the Tanzanian dicynodont Dicynodon huenei (Therapsida: Anomodontia). - PeerJ 7: e7420
Kammerer, C.F.
-
2019. The many faces of synapsid cranial allometry. - Paleobiology 45(4): 531-545
Krone, I.W., Kammerer, C.F. & Angielczyk, K.D.
-
2020. Novel endocranial data on the early therocephalian Lycosuchus vanderrieti underpin high character variability in early theriodont evolution. - Frontiers in Ecology and Evolution 7(464): 1-27
Pusch, L., Ponstein, J., Kammerer, C.F. & Frobisch, J.
