Global climate changes account for the main trends of conodont diversity but not for their final demise
Résumé
Conodonts, one of the longest-lived early groups of vertebrates, have a very complete fossil record ranging from the late Cambrian to the end of the Triassic and persisted through many global climatic and biotic events. In this paper, we analyse a large dataset harvested from the Paleobiology Database to compute global diversity curves at the generic level and explore patterns of conodont paleogeographic distribution. Our results partly confirm the most prominent findings of earlier studies including the occurrence of an Ordovician acme, a Permian nadir and a short-lived Triassic recovery. Major peaks of origination were found in the Early Ordovician and Early Triassic, while major extinctions occurred in the Upper Ordovician and Pennsylvanian. Paleogeographical extent of conodonts was impacted by i) the position of paleo-continents (notably impacting the latitudinal gradient of diversity), ii) the available continental shelf area and iii) ice sheets expansion. Diversity trends were mostly impacted by transitions between hothouse and icehouse ages, with major glaciations and associated marine regressions co-occurring with major extinctions. The influence of global sea level was less marked than that of temperature. However, the final demise of conodonts at the end of the Triassic did not coincide with either a major glaciation or marine regression. This supports the view that extinction of the group was mostly due to biotic factors such as competition with ‘Mesozoic’ taxa.
Domaines
Biodiversité et Ecologie
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