Stress-Related Evolution in Triassic Conodonts and the Middle Norian Juvenile Mortality

Conodonts are of great importance in Paleozoic and Early Triassic stratigraphy, which is proven by the large number of studies on their biostratigraphic relevance. Less emphasis was placed on the paleoecology of this group, even though environmental controls highly affect the distribution and applicability of conodonts. Few records are available from the Triassic, in which lethal or sublethal environmental stress is considered as the driving factor of evolutionary trends. Such cases are reviewed from the Permian-Triassic transition involving studies on the genera Hindeodus, Isarcicella, and Neogondolella. A summary is given on the characteristic taxa (e.g., Pseudofurnishius murcianus, Nicoraella budaensis, and Mockina slovakensis) of the Middle and Upper Triassic, which often formed monospecific faunas in the unstable environments of the restricted basins and marginal seas of the Tethys.