Exploring biodiversity evolution in tropical seas based on comparisons of the Triassic fauna of the Cassian Formation with modern faunas
Final Report Abstract
We studied the community composition of faunal assemblages from the Late Triassic Cassian Formation and compared these with other fossil and recent assemblages. Our aim was to evaluate how reef-associated and basinal tropical communities have changed since the Triassic and what effect taphonomy has on our assessment of diversity patterns. Our main hypothesis was that reef basin assemblages have not changed significantly in their principal ecological composition and diversity since the Late Triassic, and that most of the observed changes are due to taphonomic biases. Our main focus was on alpha- and gamma diversity and its sources and drivers, in the Cassian Formation and other assemblages. This project included a methodological study which was based on the analysis of Recent assemblages from the Red Sea using different mesh sizes that led to the conclusion that neither mesh sizes nor sediment depth (analyzing the uppermost 10 cm vs. the subjacent 10 cm of the bottom sediments) explains most of the observed variability. Instead, the location of the samples within the reef environments is the main predictor for diversity and composition. These results can also be applied to the Cassian paleoenvironment. Analyses of our own samples as well as a compilation of occurrences from the literature show high values of gamma, beta, and alpha diversities as well as taxon proportions comparable to those in similar modern environments. One central finding of this project is the high proportion of gastropods among the Cassian fauna, which is on par with Cenozoic and modern assemblages. We introduced a new type of fossil lagerstätte describing assemblages that feature easy extractability of fossils, called liberation lagerstätten. Liberation lagerstätten such as the Cassian Formation, which yields a high diversity of molluscs and particularly gastropods, may be key to uncovering biodiversity patterns throughout the Phanerozoic.
Publications
- 2016. Drill hole convergence and a quantitative analysis of drill holes in mollusks and brachiopods from the Triassic of Italy and Poland, Palaeogeography, Palaeoclimatololgy, Palaeoecology, 457: 342–359
Klompmaker, A. A., Nützel, A. & Kaim, A.
(See online at https://doi.org/10.1016/j.palaeo.2016.06.017) - 2018. Influence of setting, sieve size, and sediment depth on multivariate and univariate assemblage attributes of coral reef‐associated mollusc death assemblages from the Gulf of Aqaba. Facies, 64: 1–10
Hausmann, I., Domanski, H. & Zuschin, M.
(See online at https://doi.org/10.1007/s10347-018-0530-7) - 2018. New record of halimedacean algae from the Upper Triassic of the Southern Alps (Dolomites, Italy). Rivista Italiana di Paleontologia e Stratigrafia 124: 421–431
Nose, M., Schlagintweit, F. & Nützel, A.
(See online at https://doi.org/10.13130/2039-4942/10607) - 2018. Racheliella, a new mathildoid gastropod genus (Gastropoda, lower Heterobranchia) from the Late Triassic St. Cassian Formation (N Italy). Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 287/2: 207–211
Nützel, A.
(See online at https://doi.org/10.1127/njgpa/2018/0713) - 2018: The youngest ophiocistioid: a first Palaeozoic-type echinoderm group representative from the Mesozoic. Palaeontology 61: 803–811
Reich M., Stegemann T. R., Hausmann I. M., Roden V. J. & Nützel A.
(See online at https://doi.org/10.1111/pala.12392) - 2020. Drivers of beta diversity in modern and ancient reef-associated soft-bottom environments. PeerJ 8: e9139
Roden, V.J., Zuschin, M., Nützel, A., Hausmann, I. M. & Kiessling, W.
(See online at https://doi.org/10.7717/peerj.9139) - 2020. Fossil liberation: A model to explain high biodiversity in the Triassic Cassian Formation. Palaeontology 63: 85-102
Roden, V. J., Hausmann, I. M., Nützel, A., Seuss, B., Reich, M., Urlichs, M., Hagdorn, H. & Kiessling, W.
(See online at https://doi.org/10.5061/dryad.6s5651k)
