The extinction of conodonts--in terms of discrete elements--at the Triassic-Jurassic boundary

Abstract

The extinction of conodonts at the end of Triassic times is studied. The possibility of random extinetion is considered. Extinction and origination rate averages for lineages of the Phanerozoic marine invertebrates are not coherent with the dynamics of this group. Their extinction rate diminished since the Lower Triassic to the Upper Triassic, but the lineage origination rate diminished since the Ladinian as well, and the clade had negative growth rate, and the probability of extinction was high. Diffuse competition with better animal designs belonging to Paleozoic and Modern evolutionary faunas and, in a more secondary way, a decrease of available marine areas and spreading of environments with abnormal Salinity in the Western Tethys are pointed out as possible causes of their extinction.