|Title / Titel||The Early and Middle Triassic biotic recovery of marine Chondrichthyes and Osteichthyes: Diversity, palaeogeography and palaeoenvironments|
|Abstract (PDF, 14 KB)|
|Summary / Zusammenfassung||The end-Permian mass extinction wiped out more than 90% of all marine species. It was the most severe mass extinction in the Phanerozoic. Fast or slow recovery of the survival fauna and flora is still hotly debated. It has been argued that the Early Triassic biotic recovery was generally very slow and not completed until the
beginning of the Anisian (Middle Triassic). However, based on the recent research amongst others by members of the Paleontological Institute of the University of Zurich, it is now clear that at least certain groups of organisms (e.g. conodonts and ammonoids) reached their pre-extinction diversity very rapidly although with
partially high turnover rates. In order to better understand the recovery after the Permian-Triassic biotic crisis, a
detailed analysis of additional surviving taxa is important.
So far, the main research on Early Triassic biotic recovery has focused on invertebrates due to their high
abundance. The fossil record of vertebrates is much more incomplete compared to that of the invertebrates and only little is known about their recovery patterns after the end-Permian mass extinction. Fishes (Chondrichthyes, Osteichthyes) are the most common vertebrate fossils and therefore are the most useful vertebrates for such an analysis. In order to cover the extinction and rediversification dynamics of Early Triassic and Anisian fishes this project was started in April 2008. For this analysis, fish material from several classical and new Early Triassic localities is being studied. The focus is being laid on marine to brackish ichthyofaunas since they can be better stratigraphically correlated than freshwater assemblages. In the center of our research project are the marine Early Triassic fishes newly discovered in the Candelaria hills (Nevada, USA) as well as in Spiti (India) and the classic fauna from Spitsbergen (Norway).
Based on the recovery patterns of certain organism groups it seems that the Early Triassic was a time of high
environmental stress. This is also reflected by recently published C-isotope curves, which show several positive and negative shifts within this time inteval. The causes for these excursions in the C-isotopic record are still controversial. Some suggest that the negative shifts might be produced by huge releases of isotopically light carbon into the atmosphere, for example, due to massive volcanic eruptions. Prolonged volcanic activity has a high impact on the pH of the ocean and Earth’s climate, specifically global temperature. A detailed analysis of the Early Triassic relative paleotemperatures has therefore also been included in this project. A curve of the relative paleotemperature of that time interval may help to interpret the extreme C-isotope excursions as well as the extinction and rediversification patterns of the fauna and flora during the Early Triassic. Suitable, not diagenetically altered material for oxygen isotope analyses is difficult to find. However, for the present research program material (osteichthyan teeth and conodonts) of exceptionally good quality from the Early Triassic of the Salt Range (Pakistan) is available.
The goals of the ongoing project are to improve the taxonomy, systematics and phylogeny of the advanced
gnathostomian fishes, to reconstruct and analyze their spatial and chronological distribution in the aftermath of the end-Permian extinction event, and to obtain relative paleotemperature changes in space and time from
oxygen isotopic composition of biogenic phosphate.
|Keywords / Suchbegriffe||paleobiogeography, Early Triassic, evolutionary radiation, marine fishes, oxygen isotopes|
|Project leadership and contacts /
Projektleitung und Kontakte
|Funding source(s) /
|SNF (Personen- und Projektförderung)
|Duration of Project / Projektdauer||Jan 1998 to Dec 2012|