Morphological Features of Conodonts of the Genus Icriodus from the Ust’-Yarega Formation (Frasnian, Upper Devonian) of the Southern Timan, Russia

A large diversity of wide-platform conodonts of the genus Icriodus is found in the section of the Ust’-Yarega Formation (Ukhta River, outcrops 14 and 14A) of Southern Timan. This section covers the Timanian and Sargaevian boundary beds (Frasnian Stage, Upper Devonian). The mass emergence of wide-platform Icriodus is observed in deeper facies of the Sargaevian Regional Substage, compared to the shallow-water Timanian Regional Substage. It is likely that changes in feeding preferences contributed to the expansion of platforms and increased grinding surfaces in some taxa.